October 07 onwards
Thu, Oct 4, '07 
Ed McCann, LancasterElectrons in bilayer graphene


Thu, Oct 11, '07 
Benjamin Doyon, DurhamQuantum impurities in nonequilibrium steady states With the present experimental interest in quantum dots and other mesoscopic objects submitted to electric currents, an efficient theoretical framework for studying quantum impurities in nonequilibrium steady states is much needed. After reviewing the topic of quantum impurities with relevant experiments and theoretical ideas, I will present aspects of some recent progress I made. It is a new theoretical framework that I developed recently in the interacting resonant level model (IRLM). I will explain how a nonequilibrium steadystate (Hershfield's) density matrix can be defined, why it is related the physical (SchwingerKeldysh) construction of steady states, and how the dynamics can be encoded into conditions on the Hilbert space ("impurity conditions"). Then I will show how these simple but slightly abstract concepts immediately give the full perturbative series (as multiple integrals), without using Feynmann diagrams or Keldysh timeordering; I will discuss the RGimproved results in the IRLM. Finally, if time allows, I will discuss how these same concepts can be used to answer the question of integrability in equilibrium and in nonequilibrium steady states.


Thu Oct 18, '07 
Roddy Vann, YorkFrequency Splitting of Compressional Alfvén Waves


Thu, Oct 25, '07 
Matthias Schmidt, BristolInterfacial properties of colloidal platelet dispersions


Thu, Nov 1, '07 
David MacKay, CavendishSustainable Energy  Without the Hot Air


Thu, Nov 8, '07 
Julia Yeomans, OxfordSwimming with a friend at low Reynolds number


Thu, Nov 15, '07 
Kai Bongs, B'ham & HamburgCold atoms  the world of the ultracold


Thu, Nov 22, '07 
Stephen Wells, WarwickRigidity and flexible motion in biomolecules It has been known since Maxwell that a count of degrees of freedom and constraints can establish if a structure is, overall, floppy, rigid or stressed (overconstrained). The "pebble game" algorithm can rapidly identify the rigid and stressed regions of a twodimensional framework. The "Molecular Framework Conjecture" states that the "pebble game" is valid for networks with nearestneighbour and nextnearestneighbour constraints, or equivalently, to frameworks with fixed bond lengths and angles and variable dihedral angles. So, we can apply rigidity analysis to protein structures (as obtained from Xray or neutron crystallography) and identify rigid substructures. Rigidity analysis provides a natural coarsegraining for a simplified model of protein motion. This in turn allows us to address flexible (slow, lowenergy) motions in proteins using the technique of "geometric simulation". Finally, I will show an example of synergy between moleculardynamics simulation and geometric simulation in the field of protein structure prediction.


Thu, Nov 29, '07 
Seminar has been postponed 

Thu, Dec 6, '07 
Arash Mostofi, ImperialMaximallylocalised Wannier functions as building blocks of electronic structure We combine largescale, ab initio electronic structure calculations and the maximallylocalised Wannier function (MLWF) approach in order to study the electronic properties of complex nanostructures. MLWFs provide an accurate, localised, minimal basis set in which to diagonalise the Hamiltonian. In the MLWF basis, Hamiltonians for large, complex systems can be constructed directly from the shortranged Hamiltonians of smaller constituent units by performing full firstprinciples calculations on either periodicallyrepeated or isolated fragments. We apply our approach to the case of DNA helices. This work has led to the development of a new opensource code called Wannier90 [1] and opens the way to obtaining a more detailed understanding of charge transport and conductance in DNA, bringing closer the prospect of engineering its electronic structure for use in nanoelectronic circuits and biotechnology applications. [1] A.A. Mostofi et al., Wannier90: A tool for obtaining maximallylocalized Wannier functions, http://arxiv.org/abs/0708.0650, http://www.wannier.org


Thu, Jan 10, '08 
James Kirkpatrick, ImperialA multiscale approach to charge mobility simulation A multiscale approach to simulation of charge mobility is presented. Classical atomistic molecular dynamics is used to obtain morphologies. The relative orientations and positions of molecules are then used to compute charge transport parameters using semiempirical Quantum Chemical methods. Once the charge transfer rates are known, simulation of charge mobility are performed on a non cubic lattice. This approach is used to compute the temperature dependence of mobility in the discotic liquid crystal hexabenzocoronene. Some remarks will be made on the time dependence of charge transport parameters in the conjugated polymer polypyrrole.


Thu, Jan 17, '08 
Petr Denissenko, WarwickFloaters, waves, and the surface tension We argue theoretically and demonstrate experimentally that in a standing wave floating particles drift towards the nodes or antinodes depending on their hydrophilic or hydrophobic properties. We explain this effect as the breakdown of Archimedes law by a surface tension, which creates a difference between the masses of the floater and displaced liquid, making the particle effectively inertial. We show analytically and confirm experimentally that the drift appears as a second order effect in wave amplitude. We investigate how the inertial effects change the statistics of floater distribution in the case of random surface waves.


Thu, Jan 24, '08 
Dimitri Gangardt, BirminghamHard core bosons in expansion: dynamics, correlations and relaxation


Thu, Jan 31, '08 
Andrew Archer, LoughboroughDynamical density Functional Theory: Dynamics of inhomogeneous liquids and glasses


Thu, Feb 7, '08 
Neil Wilson, WarwickElectronic transport in carbon nanotube networks


Thu, Feb 14, '08 
Dieter Vollhardt, AugsburgMetalInsulator Transitions of Correlated Lattice Fermions with Disorder 

Thu, Feb 21, '08 
Andrea Gamba, TorinoDomain coarsening in eukaryotic directional sensing The cells of multicellular organisms are endowed with a chemical compass of amazing sensitivity, formed as a result of billions of years of evolution. Concentration differences of the order of a few percent in attractant chemicals from side to side are sufficient to induce a chemical polarization of the membrane leading to cell migration towards the signal source. It has been realized recently that this early polarization process is the result of a phaseseparation instability in a well characterized network of diffusioncontrolled chemical reactions. We give a universal description of this early symmetry breaking process. Our description implies the existence of two clearly separated polarization regimes depending on the presence or absence of an anisotropic component in the activation pattern, and the existence of a sensitivity threshold for the anisotropic component. In particular, we find that the polarization time t_{ε} in the presence of an anisotropic extracellular signal depends on the anisotropy degree ε through the power law t_{ε} α ε^{2}, and that in a cell of radius R there should exist a threshold value ε_{th} α R^{1} for the smallest detectable anisotropy. Our results are in agreement with existing experimental data and explain the recent observation of a threshold in the degree of detectable anisotropy.


Thu, Feb 28, '08 
Paul Fendley, Virginia & OxfordTopological Quantum Computation from NonAbelian Anyons


Thu, Mar 6, '08 
Ana Lopez, OUCE OxfordFrom climate models to impacts of climate change: can we predict anything with any confidence?


Thu, Apr 24, '08 
Paul Tangney, ImperialDynamic sliding friction between coaxial carbon nanotubes


Thu, May 1, '08 
Martin Plenio, ImperialEntanglement: From scaling laws to simulations


Thu, May 8, '08 
Rudolf Roemer, WarwickCharge Migration in DNA, p53 and other speculations


Thu, May 15, '08 
Rosalind Allen, EdinburghSimulating the flipping of the bacteriophage lambda genetic switch


Thu, May 22, '08 
David Dunstan, QMULQuenching of the Inversion Transition of Ammonia  A Classical or Quantum Problem?


Thu, May 29, '08 
Andrew Ho, RHULFeshbach resonance and multiband physics in ultracold atoms trapped in optical lattices


Thu, Jun 5, '08 
Dmitriy Krizhanovskii, SheffieldIntrinsic decoherence mechanisms in the microcavity polariton condensate


Wed, Oct 1, '08 
John Dixon meetingScientific Meeting and Celebration in Honour of Dr. John Dixon 10.30 Conducting properties of the cytoskeleton and internal signal propagation in neurons Jack Tuszynski, University of Alberta 11.00 Old and new aspects of the JahnTeller Effect 12.00 Dynamics at the Nanoscale, as seen by Physicist and Biologist 12.30 Magnetic Interactions and Magnetic Resonance: Examples from the Solid State NMR Group at Warwick


Thu, Oct 2, '08 
Stephen Powell, OxfordClassicalquantum mappings for unconventional phase transitions in geometrically frustrated systems


Thu, Oct 9, '08 
Robin Ball, WTG & ComplexityQuantifying Emergent Behaviour


Thu, Oct 16, '08 
Christopher Mudry, PSIElectron fractionalization in twodimensional graphenelike structures


Thu, Oct 23, '08 
Suzanne Fielding, ManchesterPhase transitions in sheared complex fluids


Thu, Oct 30, '08 
Mario Nicodemi, WTG & ComplexityOn X Chromosome Inactivation


Thu, Nov 6, '08 
Peter Krueger, NottinghamLow dimensional physics with cold atoms


Thu, Nov 13, '08 
Kostya Trachenko, CambridgeUnderstanding liquids and glass transition on the basis of elastic interactions


Thu, Nov 20, '08 
Magnus Richardson, Systems BiologyMathematical models of cortical neurons


Thu, Nov 27, '08 
Arthur Peeters, CFSAMomentum transport due to small scale turbulence in a fusion device


Thu, Dec 4, '08 
Nick Jones, OxfordDynamic Communities in Multichannel Data Network communities are sets of nodes in a network that are connected to each other more than they are to the rest of the network. We investigate the clustering dynamics of multichannel (multivariate) time series by first representing their correlations as timedependent networks and then examining the evolution of network communities. To do this, we employ a nodecentric approach that allows us to track the functional roles of individual nodes in time without having to track entire communities. As an example, we consider a foreign exchange market network in which each node represents an exchange rate and each edge represents a timedependent correlation between the rates. Using dynamical community detection, we find that exchange rates with strong intracommunity connections are persistently assigned to communities with the same set of nodes.


Thu, Dec 18, '08 
IoP TCM Group MeetingDaan Frenkel, Department of Chemistry, Cambridge, 'Dense Packing and Beyond'; Jorge Kurchan, PMMH, Ecole Superieure PCI, Paris, 'Jamming versus Glass Transitions' 

Thu, Jan 8, '09 
Paola Carbone, ManchesterMultiscale simulation of macromolecules: static and dynamic properties from equilibrium and nonequilibrium simulations


Thu, Jan 15, '09 
Thomas Fernholz, NottinghamA quantum interface between light and atomic ensembles


Thu, Jan 22, '09 
Gunnar Moeller, CambridgeThe composite particle approach to quantum Hall bilayers at filling one


Thu, Jan 29, '09 
Fabian Essler, OxfordLocal Density of States in 1D Mott insulators with a Boundary


Thu, Feb 5, '09 
Buitelaar, POSTPONED UNTIL 30/4/09Spin Physics in Carbon Nanotube Double Quantum Dots


Thu, Feb 12, '09 
Sergei Fedotov, ManchesterAnomalous diffusion, reactions and random walk models


Thu, Feb 19, '09 
Feliciano Giustino, OxfordPhonon contribution to the photoemission kink in cuprate superconductors


Thu, Feb 26, '09 
Mike Cates, EdinburghLiving Colloids: Dynamics of Bacterial Suspensions


Fri, Feb 27, '09 
Massimo Inguscio, FlorenceAGN (Bhamrelay) Ultracold atoms in optical lattices


Thu, Mar 12, '09 
Yury Sherkunov, WarwickOptimum electron entangler at low temperatures


Thu, Apr 23, '09 
Martin McCall, ImperialNegative Refraction: Causality, Relativity and Controversy


Thu, Apr 30, '09 
Mark Buitelaar, CambridgeSpin Physics in Carbon Nanotube Double Quantum Dots


Thu, May 7, '09 
Daphne Klotsa, NottinghamStructure formations of macroscopic spheres in oscillatory fluid flows Recently there has been a lot of interest in the collective behaviour and pattern formation in granular matter [1], which can be enhanced by the presence of a fluid. We are interested in the fluidmediated interactions between macroscopic rigid particles under sinusoidal vibration in a liquidfilled cell. Various patterns and structures in these flows had been reported [2,3] but the exact details remained unknown. At finite Reynolds numbers the oscillatory motion of a rigid object gives a nonzero timeaveraged flow, called steady streaming. We have studied pairs of equalsized spheres which are found to align perpendicular to the direction of oscillation with a welldefined gap between them [4]. Consequently multiple particles form chain patterns aligned across the direction of vibration. These systems have been investigated both in experiment and in simulation. We show that the mechanisms responsible for these effects can be traced to the streaming flows induced by the motion of the solid spheres relative to the fluid [5]. [1] I. S. Aranson and L. S. Tsimring, Reviews of Modern Physics, 78, 641 (2006); [2] R. Wunenburger, V. Carrier and Y. Garrabos, Physics of Fluids, 14, 2350 (2002); [3] G. A. Voth, B. Bigger, M.R. Buckley, W. Losert, M. P. Brenner, H. A. Stone and J. P. Gollub, Phys. Rev.Lett., 8, 234301, (2002); [4] D. Klotsa, M. R. Swift, R. M. Bowley and P. J. King, Phys. Rev. E, 76, 056314 (2007); [5] D. Klotsa, M. R. Swift, R. M. Bowley and P. J. King, Phys. Rev. E, 79, 021302 (2009).


Thu, May 14, '09 
Alexey Kavokin, SouthamptonSpin effects in superfluids of excitonpolaritons


Thu, May 21, '09 
Mike Evans, LeedsStatistical mechanics in complex fluids under shear: prediction and measurement


Thu, May 28, '09 
Alessandro Troisi, WarwickModelling charge transport in soft materials: old and new physics


Thu, Jun 11, '09 
Jin Zhang + Adam SwetnamFull Counting Statistics in a Quantum Point Contact, Jin Zhang
Monte Carlo Simulations of Polymers, Adam Swetnam


Thu, Jun 25, '09 
Dr. Pragya Shukla (Indian Institute of Technology, Kharagpur, India and ICTP, Trieste)Universality in Complexity: A Generalized Random Matrix Approach Physical systems can be complicated. Lack of detailed knowledge of their interactions can be represented by randomness in generators of the dynamics. In waves (quantum, electromagnetic, etc.) the associated operators can be modelled by random matrices. 
Thu, Oct 7, '10 
Hierarchy of models for entangled polymers I will review the multiscale approach to modelling of entangled polymers, which includes molecular dynamics (MD), single chain stochastic models (slipsprings) and the tube model. After that I will concentrate on the link between many chain (MD) and single chain models. I will report results from molecular dynamics simulations on stress relaxation and show the detailed comparison with slipspring model. In the second part of the talk I will turn to the issue of microscopic definition of entanglement in molecular dynamics. We propose to define entanglement as a longlived contact between mean paths of the two chains. Using this definition, we present empirical evidence and statistical properties of such entanglements, and discuss the implications for the tube theory and the slipspring model. 
Thu, Oct 14, '10 
Ground state factorization versus frustration in spin systems We investigate the existence of factorized ground states in Heisenberglike quantum spin models with antiferromagnetic interactions of arbitrary range and exhibiting a varying degree of frustration. After reviewing a method developed for frustrationfree systems based on tools from quantum information theory, we extend it to characterize the competition between frustration and ground state factorization. Low frustration is shown to signaled by the existence of factorized ground states at specific values of the external field, while for higher frustration degrees the factorized eigenstates do not minimize the energy, leaving necessarily room for entanglement in the ground state. The compatibility threshold, characterizing the frustrationdriven transition between order (factorization) and disorder (correlation), is investigated and exact analytical factorized solutions are obtained for shortrange as well as infiniterange frustrated quantum magnets.Ground state factorization is thus revealed as an effective tool to probe quantum frustration in cooperative systems. 
Thu, Oct 21, '10 
Solitons and vortex lattices with microcavity polaritons I am going to report our recent results on two aspects of nonlinear physics of microcavity polaritons. First, is the twodimensional localization of exciton polaritons in a coherently pumped semiconductor microcavity operating in the strongcoupling regime. 2D polaritonsolitons can exist despite the fact that the effective mass of linear polaritons has the opposite signs along the orthogonal directions in the momentum space. Nonlinearities compensating the opposing mass signs have different physical origin, but act simultaneously. They are due to repulsion of polaritons, which compensate the negative mass effects, and due to parametric fourwave mixing, which compensate the positive mass effects. Both of these nonlinearities support their respective families of onedimensional solitons, which coexist one with another and with 2D solitons. Second part of my talk is about vortex lattices of exciton polaritons in microcavities operating in the fourwave mixing regime. These lattices can be practically seeded by a weak signal pulse formed by a superposition of three interfering beams and can be either very robust or can melt through annihilation of vortexantivortex pairs. 
Fri, Oct 22, '10 
Current Conservation in NonEquilibrium Networks For QuantumHallSystems network models have been successfully used to investigate questions of localizations as well as the distribution of electrochemical potentials. While the wellknown ChalkerCoddington network model [1] , which uses elastic single particle quantum tunneling at saddle points to obtain critical exponents, was used for the former task, in the latter the nonequilibrium network model [24], which describes quantities of nonquilibrium thermodynamics via the LandauerBÃ¼ttiker approach, was used. In case of local linear transport at saddles we show that the chemical potential distribution can be obtained, respecting the boundary condition of injected currents, from an inhomogeneous system of linear equations. It turns out that the solution is uniquely determined by the boundary condition, no matter how many current contacts we have. The seaming contradiction can be resolved by the fact that current is automatically conserved due to the formulation of the network. [1] J. T. Chalker and P. D. Coddington, â€œPercolation, quantum tunnelling and the integer Hall effectâ€œ, J. Phys. C: Solid State Phys. 21, 2665 (1988). [2] J. Oswald, â€œA new model for the transport regime of the integer quantum Hall effect: The role of bulk transport in the edge channel pictureâ€ﾝ, Physica E 3, 30 (1998). [3] J. Oswald and M. Oswald, â€œCircuit type simulations of magnetotransport in the quantum Hall effect regimeâ€œ, J. Phys.: Condens. Matter *18*, R101 (2006). [4] C. Uiberacker, C. Stecher, and J. Oswald, â€œ/Systematic study of nonideal contacts in integer quantum Hall systems/â€ﾝ, Phys. Rev. B *80*, 235331 (2009). 
Fri, Oct 29, '10 
Natural Mode Entanglement as a Resource for Quantum Dense Coding Natural particlenumber entanglement resides between spatial modes in coherent ultracold atomic gases. However, operations on the modes are restricted by a superselection rule that forbids coherent superpositions of different particle numbers.? This seemingly prevents mode entanglement being used as a resource for quantum communication. In this talk, I will demonstrate that mode entanglement of a single massive particle can be used for dense coding despite the superselection rule. I will show that the full quantum channel capacity is achieved if both parties share a coherent particle reservoir. The talk is based upon results in L. Heaney and V. Vedral, Phys. Rev. Lett. 103, 200502 (2009). 
Thu, Nov 4, '10 
Andrew Morris, UCL, Materials Discovery Using ab initio Random Structure Searching 
Thu, Nov 11, '10 

Thu, Nov 18, '10 
Manuel dos Santos Dias; WeiChang Lo, Competing Interactions and Chiral Magnetism in Mn Monolayers on Transition Metal Substrates: A FirstPrinciples Approach and Dynamics of Entangled Ring Polymers: A Hint of New Glassy Materials, WeiChang Lo 
Thu, Nov 25, '10 
Beyond the Quantum 
Thu, Dec 2, '10 
Vortex interactions in two component GinzburgLandau theory and type 1.5 superconductivity 
Thu, Dec 9, '10 
Ramin Golestanian, Oxford, The directed propulsion of small scale objects in water is problematic because of the combination of low Reynolds number and strong thermal fluctuations at these length scales. I introduce simple prototypes of model low Reynolds number swimmers and examine their physical properties. I also discuss a number of recent experimental realizations of such devices. 
Fri, Dec 10, '10 

Thu, Jan 20, '11 
Quantum optics with an atomic vapour: entangled images and superresolution The entanglement properties of two beams of light can reside in subtle correlations that exist in the unavoidable quantum fluctuations of their amplitudes and phases. I will review recent advances in fourwave mixing in an atomic vapour which have enabled the production and the observation of "entangled images", that is to say beams of light which are entangled "point per point" across their transverse profiles. These beams can carry quantum information not only in their average profile but also in their spatial details, opening up the field of quantum imaging. The introduction of the spatial degrees of freedom into quantum optics lets us envision novel applications for quantum light. As an example, I will present our current efforts to improve optical superresolution beyond the standard quantum limit. 
Thu, Feb 3, '11 
Efficient sampling of atomic configurational spaces using Nested Sampling 
Thu, Feb 10, '11 
Vortex interactions in two component GinzburgLandau theory and type 1.5 superconductivity 
Thu, Feb 17, '11 
Stripe Order and Pairing in the Cuprate Superconductors 
Thu, Feb 24, '11 
Exploring the structural properties and molecular mechanisms of cryoprotectants Many organisms that live in extreme environments have developed mechanisms that protect them from environmental stresses. A common mechanism involves accumulation of sugars, known as protecting osmolytes, which allow organisms to survive subzero temperatures. This method is widely utilized in industry, medicine and nanotechnology to prolong the storage life of specific components. One such protecting osmolyte is glycerol, a sugar alcohol with three hydroxyl group, which is a rich and complex system for the study of hydrogen bonded fluids. While much work has been done to characterise glycerolâ€™s dynamic properties a corresponding thorough examination of the structural properties of this molecule is lacking. In particular, little is known about the structural architecture of glycerolâ€™s hydrogen network in aqueous solution. Furthermore, the molecular mechanism by which cryoprotectants like glycerol stabilise biological molecules is yet to be elucidated. We have completed a series of neutron diffraction experiments combined with computational modelling to reveal insight into the structural properties of this important system. We have completed a range of single molecule force spectroscopy experiments to probe the mechanical stability of proteins in cryoprotectant environments. By combining these two approaches we hope to shed light onto the molecular mechanisms of cryoprotection. 
Thu, Mar 3, '11 
The Trouble with Critical Wetting A longstanding problem in condensedmatter physics concerns the nature of the critical wetting transition in threedimensional systems with shortranged forces. The controversy focused originally on the discrepancy between predictions of strongly nonuniversal critical effects, based on renormalization group analysis of an interfacial Hamiltonian, and Monte Carlo studies of wetting in the 3D Ising model, which are instead broadly consistent with meanfield expectations. This gulf between theory and simulation was widened further by subsequent refinements of the interfacial model which appeared to show that fluctuations should necessarily drive the transition firstorder. This prediction is in qualitative disagreement with the simulation studies and would radically alter the anticipated structure of the global surface phase diagram. We review recent progress made towards overcoming these problems using a new nonlocal interfacial Hamiltonian. This model, which may be derived systematically from a more microscopic theory and also applied to wetting at structured (nonplanar) substrates such as wedges, allows for the presence of twobody interfacial interactions in the wetting layer. These are characterised by an additional diverging coherence length, missing in previous descriptions of wetting. This serves to cutoff the spectrum of interfacial fluctuations that describe the repulsion of the interface from the wall which, in turn, slows down the onset of critical effects (nonuniversality) and explains why the transition is not driven firstorder, therefore preserving the structure of the global surface phase diagram. 
Thu, Mar 10, '11 
Novel superfluid phenomena in semiconductor microcavities 
Thu, Mar 17, '11 
Topological invariants and topological insulators Since their characterization over 80 years ago, physicists have believed that there is only one type of band insulator  a filled valence band below the Fermi energy with a gap to excitations in the conduction band above the Fermi energy. In the past few years, it has become clear that this is not the whole story: band insulators have topological invariants that distinguish them from each other, and phase transitions must separate insulators with different values of these invariants. Insulators with nontrivial values of these invariants have come to be known as "topological insulators." In this talk I will give simple physical descriptions of these invariants, discuss their implications, and examine the experiments that have actually observed topological insulators. Application of these topological ideas has more recently led to a similar classification of topological superconductors and superfluids, some of which are well known, and others of which have yet to be observed. Finally, I will discuss further applications of topological invariants, as well as current and future directions. 
Thu, May 5, '11 
Symmetrybroken QH states in Bilayer Graphene Bilayer graphene has attracted considerable interest due to the important role played by manybody effects, particularly at low energies. The exceptional quality of suspended devices has enabled the observation of interactiondriven brokensymmetry states and the fractional quantum Hall effect. Here we report local compressibility measurements of a suspended graphene bilayer. We find that the energy gaps at filling factors nu = 4 do not vanish at low fields, but instead merge into an incompressible region near the charge neutrality point at zero electric and magnetic field. These results indicate the existence of a zerofield ordered state and are consistent with the formation of either an anomalous quantum Hall state or a nematic phase with broken rotational symmetry. At higher fields, we measure the intrinsic energy gaps of brokensymmetry states at nu = 0, 1 and 2, and find that they scale linearly with magnetic field, yet another manifestation of the strong Coulomb interactions in bilayers. Coauthors Benjamin E. Feldman, R. Thomas Weitz, Monica T. Allen, Amir Yacoby 
Tue, May 10, '11 
Rogue Wave Solution for the NLS and DNLStype Equations In this talk, the variable coefficient nonlinear Schrodinger equation (VCNLSE), derivative nonlinear Schrodinger equation (DNLSE) and variable coefficient derivative nonlinear Schrodinger equation(VCDNLSE) are discussed. The rogue wave solution of VCNLSE, DNLSE and VCDNLSE are given. The DNLSE is solved by Darboux transformation. The solutions of VCNLSE (VCDNLSE) are given from known solutions of NLSE (DNLSE) by a transformation developed by us recently. Several figures for these solutions are plotted to understand intuitionally its dynamical evolution. 
Thu, May 12, '11 
Kyriakos Porfyriakos, Oxford (POSTPONED), On Endohedral C60 
Thu, May 19, '11 
Random search: a tool for physics discovery 
Thu, May 26, '11 
Evaporative dewetting of suspensions  closetoequilibrium approaches from DDFT to thin film hydrodynamics 
Thu, Jun 2, '11 
Endohedral Fullerenes as Building Blocks for a Quantum Computer Endohedral fullerenes offer a unique paradigm in nature: the encapsulation of atom(s) in spherical molecular structures. The encapsulated atoms bestow extraordinary properties to the fullerene cage. Many endohedral fullerenes have unpaired electrons. Electrons can carry quantum information embodied in their spinstate. Hence endohedral fullerenes have been proposed as quantum bits or â€œqubitsâ€ﾝ: the building blocks of a quantum information processing (QIP) device. N@C60 in particular is a remarkable molecule with the longest coherence time ever recorded for a molecular system (its electron spin coherence time T2 has been measured in excess of 0.24 ms 1). This property makes this molecule especially attractive for QIP. Moreover, the electronic properties of endohedral fullerenes can be tuned by appropriate chemical functionalization. In this talk, I will endeavour to explain the basic principles of QIP and the suitability of endohedral fullerenes as building blocks for a quantum computer (see Figure 1). I will describe what a fullerene based quantum computer might look like and how it could be made. Of particular importance is the scalability of such a device. I will show how scalable molecular structures can be built. I will review the stateoftheart materials science with endohedral fullerenes with emphasis on N@C60.2 I will highlight the particular challenges that are involved in working with N@C60 and how these can be overcome. 
Tue, Jun 7, '11 
IoP TCM Group Annual Meeting 2011 PLT Ivo Souza, San Sebastian, Orbital magnetoelectric coupling in insulators Insulators with magnetic order and lacking a center of spatial inversion can display a linear magnetoelectric (ME) effect, whereby an applied electric field induces a firstorder change in the magnetization. In conventional magnetoelectrics such as Cr2O3 the ME coefficient is dominated by the spinmagnetization response, but a complete description should also take into account the induced orbital magnetization. I will describe the theoretical framework for calculating the orbital ME response. Remarkably, it contains a contribution which is purely geometric, in that it can be expressed solely in terms of the Berry potential and Berry curvature of the Bloch states in kspace. Like the Berryphase polarization, this geometric ME coupling is only welldefined modulo a quantum of indeterminacy. While the geometric ME coupling is typically small in conventional magnetoelectrics, in strong topological insulators such as Bi2Se3 it equals half the quantum, which amounts to a rather large ME coupling. Some preliminary firstprinciples calculations of the orbital ME tensor will be reported. Lorna Dougan, Leeds, Exploring the structural properties and molecular mechanisms of cryoprotectants Many organisms that live in extreme environments have developed mechanisms that protect them from environmental stresses. A common mechanism involves accumulation of sugars, known as protecting osmolytes, which allow organisms to survive subzero temperatures. This method is widely utilized in industry, medicine and nanotechnology to prolong the storage life of specific components. One such protecting osmolyte is glycerol, a sugar alcohol with three hydroxyl group, which is a rich and complex system for the study of hydrogen bonded fluids. While much work has been done to characterise glycerolâ€™s dynamic properties a corresponding thorough examination of the structural properties of this molecule is lacking. In particular, little is known about the structural architecture of glycerolâ€™s hydrogen network in aqueous solution. Furthermore, the molecular mechanism by which cryoprotectants like glycerol stabilise biological molecules is yet to be elucidated. We have completed a series of neutron diffraction experiments combined with computational modelling to reveal insight into the structural properties of this important system. We have completed a range of single molecule force spectroscopy experiments to probe the mechanical stability of proteins in cryoprotectant environments. By combining these two approaches we hope to shed light into the molecular mechanisms of cryoprotection. Eugene Demler, Harvard, Learning about order from noiseThe probabilistic character of measurement processes is one of the most fascinating aspects of quantum mechanics. In manybody systems quantum noise can reveal the nonlocal correlations and multiparticle entanglement in the underlying states. In this talk I will review recent theoretical and experimental progress in the quantum noise analysis of many body states of ultracold atoms. I will discuss applications of this technique to the study of one dimensional systems in and out of equilibrium, fermionic pairing near Feshbach resonances, and magnetism in optical lattices. Jonathan Keeling, St Andrews, Condensation, superfluidity and lasing of coupled lightmatter systems, Microcavity polaritons are a system that can show coherence in a stronglycoupled light matter system at low temperatures. As such, they connect both to BoseEinstein condensation and also to lasing, and they currently provoke a number of questions about what properties such a non equilibrium superfluid might have. I will present an approach to modelling such non equilibrium condensates, and use this model to extract a number of properties addressing these questions: Firstly, I will show what ingredients allow the polariton system to show coherence while remaining in the strong coupling regime (and remaining far below the inversion required for normal lasing). Secondly, I will discuss various aspects of superfluidity in a nonequilibrium twodimensional light matter system; in particular, power law correlations in the infinite system, and how these are modified in a finite system. I will also discuss the relation between different aspects of superfluidity that should be seen in such nonequilibrium systems, and propose an approach to answering more clearly the question of whether the polariton system is superfluid. 
Tue, Jul 5, '11 
Solution of quasispecies models using coherent states Quasispecies models describe the evolution of an asexually reproducing population subject to random mutation and selection. Individuals are labelled by a DNAlike string of letters of a fixed length N, and the population is described by a distribution function on the set of possible strings. Quasispecies models are a popular starting point for theoretical studies of molecular evolution, and have recently been applied to studies of virusimmune system interactions, evolution in changing environments, and extended to include sexual reproduction. Two of the most commonly studied quasispecies models can be mapped onto a quantum spin system similar to the onedimensional quantum Ising model, which allows the application of several techniques from statistical physics. Here I present a new method for calculating the dynamics and equilibrium population distribution in these quasispecies models by constructing a spin coherentstate path integral representation of the evolution operator. In the large N limit a semiclassical approximation gives a description in terms of a classical Hamiltonian function on a sphere. Using this method I will present several new results relevant to biological systems including evolution of the mutation rate, adaptation in changing environments, and a model of escape from adaptive conflict. 
Thu, Jul 7, '11 
How FirstPrinciples Calculations Combined with ^{95}Mo SolidState NMR Can Help in the Understanding of Inorganic Materials (Joint Seminar with NMR) Since the 1980s, the expansion of solidstate NMR has increased significantly owing to the development of new techniques that enable high resolution to be achieved even in the solid state. For inorganic compounds without protons or fluorine atoms, the two dominant interactions responsible for the appearance of the NMR spectrum are the chemical shift anisotropy and the quadrupolar interaction tensors. These parameters give information about the atomic structure of the compound under investigation. It appears that in many cases, the complexity of the experimental results require a theoretical analysis for their complete understanding. Until recently, only quadrupolar interaction parameters could be calculated using periodic DFT calculations. Pickard and Mauri presented a formalism, named GIPAW, for the ab initio calculation of allelectron NMR chemical shifts in insulators using pseudopotentials. We present the combined application of 95Mo solidstate NMR and DFT calculations for the study of materials such molybdenum cluster compounds and nanoparticles. The power of this combined approach for the investigation of solidstate materials will be shown as well as its limitations. 
Thu, Oct 6, '11 
Protons to planets: Materials simulation as a window into planetary processes Most planets are so large that their characteristic pressure exceeds by orders of magnitude current experimental capability. The behavior of materials in this regime is poorly understood, but likely to be rich, with important implications for our understanding of planetary formation and evolution. The discovery of exoplanets and the development of high energy density experiments motivate a closer look. We have been using density functional theory, combined with molecular dynamics and lattice dynamics to study materials in this extraordinary regime. I will explore two cosmically abundant planetary constituents at pressures up to 1 Gbar and temperatures up to 5 eV: helium and iron, focusing on changes in the electronic structure with compression and heating, including gap closure and changes in Fermi surface topology, and the connection between electronic structure and physical properties such as fluid or crystalline structure and electrical conductivity that may have important implications for the thermal evolution of planets and the generation of magnetic fields. 
Thu, Oct 13, '11 
Meera Parish, TCM CambridgePS1.28 Highly polarized Fermi gases in different dimensions In this talk, I will consider an atomic Fermi gas in the limit of extreme spin imbalance, where one has a single spindown impurity atom interacting attractively with a spinup atomic Fermi gas. Such a scenario is an example of the canonical "polaron" problem, the solution of which is used to construct the lowenergy behavior of manybody systems. For sufficiently strong attraction, the impurity atom has the possibility of binding one or more spinup fermions and thus changing its statistics. I will explore the nature of these binding transitions and how they are affected by the system dimensionality. 
Thu, Oct 20, '11 
Jiannis Pachos, LeedsPS1.28 Seeing Topological Order Different phases of matter can be distinguished by their symmetries. This information is captured by order parameters that summarize the essential properties of the phase. Order parameters are usually defined in terms of local operators that can be measured in the laboratory. Topological insulators are materials with symmetries that depend on the topology of the energy eigenstates of the system. These materials are of interest because they can give rise to robust spin transport effects with potential applications ranging from sensitive detectors to quantum computation . However, direct measurement of topological order has been up to now impossible due to its nonlocal character. In this talk we provide a general methodology to perform a direct measurement of topological order in cold atom systems. As an application we propose the realisation of a characteristic topological model, introduced by Haldane, using optical lattices loaded with fermionic atoms in two internal states. We demonstrate that timeofflight measurements directly reveal the topological order of the system in the form of momentum space skyrmions. 
Thu, Oct 27, '11 
Igor Mekhov, Clarendon LabPS1.28 Quantum optics of quantum manybody systems 
Thu, Nov 3, '11 
Aron Cohen, CambridgeDensity Functional Theory: from the Hydrogen atom to strongly correlated physics 
Tue, Nov 8, '11 
Glenn Martyna, IBMPS1.28 Simulation and modelling of materials with atomic detail at IBM: From biophysics to hightech application 
Thu, Nov 10, '11 
Vlado Lazarov, YorkPS1.28 Atomic and Electronic Structure of Polar Oxide Films and Interfaces Intrinsic polar materials, such as metaloxides and compound semiconductors, are some of the most commonly used materials in electronic, magnetic, and chemical applications.It has been recognized for some time that polarity arising from chemical variations at surfaces and interfaces is the main driving force determining the structural and electronic properties of nanoscale materials. In this talk I will discuss the possible mechanism of polar oxide film growth on case of MgO(111), as well as atomic and electronic structure of polar oxide/oxide and polar oxide/semiconductor interfaces. Also I will give examples how the interface polarity can be effectively use for stabilisation of metastable thin film phases such as cubGaN(111)/MgO(111), and large band offsets engineering at polar oxide/semiconductor interfaces. 
Thu, Nov 17, '11 
Fabian Essler, POSTPONEDPS1.28 tba 
Thu, Nov 24, '11 
Matthias Bollhoefer, TU BraunschweigFast Algebraic Solvers for LargeScale Linear Systems and Eigenvalue Problems In this talk I will discuss algebraic approaches to solving largescale linear systems and largescale eigenvalue problems efficiently. The techniques, which I will discuss, have in common that they implicitly use information about the analytic model, while the approach itself is algebraic and uses only a few key parameters. The talk will give an overview of two approaches. One is based on hierarchical matrix approximation techniques. The other uses multilevel incomplete factorization. For a large class of partial differential equations, and related problems, these approaches allow us to solve linear systems of equations and eigenvalue problems easily with only minor problemspecific changes. 
Thu, Dec 1, '11 
Nic Shannon, Bristol/OxfordPS1.28 Angleresolved NMR The simple fact that nuclear and electronic spins interact makes NMR one of the most powerful probes of solid state magnetism. In particular, changes in NMR spectra provide vital information about magnetic order in cases where small sample size or extreme conditions render neutron scattering impossible. However as a probe of magnetic excitations, NMR is famously difficult to interpret, since excitations with many different momenta are mapped onto a single nuclear spin relaxation time. Here we revisit the existing theory of the NMR T1 relaxation rate in magnetic insulators, and show how this can be extended to take account of the tensor structure of dipolar and transferred hyperfine interactions with nuclear spins. This tensor interaction makes relaxation rates sensitive to the initial orientation of nuclear spins, and as a consequence, both the magnitude and the temperature dependence of the T1 depend on the orientation of the magnetic field used to carry out the experiment. We demonstrate that this theory is in quantitative agreement with existing data for the collinear antiferromagnets BaFe2As [1] and Li2VOSiO4, and make explicit predictions for the angledependence of T1 in the squarelattice antiferromagnets La2CuO4 and YBa2Cu3O6, and the triangular lattice antiferromagnet VCl2. We also explore how these ideas might be used to distinguish uncoventional forms of magnetic order, including spin nematic states which cannot be resolved by their static properties alone. [1] A. Smerald and Nic Shannon, Europhys Lett 92, 47005 (2010), [2] A. Smerald and Nic Shannon, arXiv:1109.0384 [accepted for publication in Phys. Rev. B] 
Thu, Dec 8, '11 
Gareth Alexander, WarwickOn Smectics in Curved Spaces (tentative title) 
Wed, Jan 18, '12 
Josh Berryman, LuxembourgPS1.28 Sampling Rare Events in NonStationary Dynamics Study of rare events such as nucleation or arrest in nonequilibrium physics is ever more fashionable, but existing rare event methods intended to enhance sampling (such as umbrella sampling and FFS) are not usually practical for general nonequilibrium conditions (away from both stationary and metastable states). A novel method for calculating the timeseries of the probability of a rare event is presented which is designed for these conditions. The method is validated for the cases of the GlauberIsing model under timevarying shear flow, the KawasakiIsing model after a quench into the region between nucleation dominated and spinodal decomposition dominated phase change dynamics, and also for the parallelopen asymmetric exclusion process. The method requires a subdivision of the phase space of the system: it is benchmarked and found to scale well for increasingly fine subdivisions, meaning that it can be applied without detailed foreknowledge of the physically important reaction pathways. 
Thu, Jan 19, '12 
Fabian Essler, OxfordQuantum Quench in the Transverse Field Ising Chain I discuss the time evolution of observables in manyparticle systems after a quantum quench, i.e. the sudden change of a parameter characterizing the Hamiltonian. I focus on the case of one dimensional systems, where recent experiments on cold atomic gases have found very unusual behaviour. I show that for the example of the transverse field Ising chain the behaviour of the system at late times after the quench can be understood in terms of a stationary state that is described by a "generalized Gibbs ensemble". 
Thu, Feb 2, '12 
Phil King (St. Andrews)PS1.28 An ARPES View of Topological Insulator Surfaces Topological insulators (TIs) are a recently discovered form of quantum matter characterized by a bulk band inversion driven by strong spinorbit coupling. They maintain a band gap in the bulk, but unusually possess unconventional surface states which are guaranteed to be metallic. Angleresolved photoemission (ARPES) is an ideal tool to study the detailed electronic structure of these surface Dirac fermions. I will present our recent ARPES measurements of the Bichalcogenide family of TIs. While several of these compounds suffer from degenerate ntype selfdoping, we show that Terich ternary compounds can have an insulating bulk. Thus, these are model examples of true topological insulators, where only a single topological surface state intersects the chemical potential. By adsorbing ntype dopants at the surface of several TIs, we mimic the effects of an externallyapplied gate voltage, of the form desirable for electronic applications. We create a twodimensional electron gas (2DEG) that coexists with the topological surface state and can be driven to develop a large Rashba spinsplitting, suggesting potential for its application in advanced spintronic devices such as the spintransistor. The tuneable surface band bending also provides a novel opportunity to probe the interplay of quantization and topological order. 
Thu, Feb 9, '12 
Robert Best, CambridgeInterpreting single molecule folding experiments: insights from molecular simulation A unique capability of single molecule experiments is the unambiguous resolution of conformational substates of biomolecules and their rates of interconversion. However, these experiments usually probe a single observable, such as a distance, and therefore specific structural information is limited. I will describe how coarsegrained molecular simulations can be used to fill in some of the details. First, I will show how coarsegrained models can be used to suggest structures for the misfolded states of titin polyproteins which are observed in singlemolecule FRET experiments. The structures of the misfolds explain their unusual stability, and are also consistent with earlier measurements by AFM. Secondly, I will consider the analysis of folding kinetics in single molecule pulling experiments, focussing mainly on the interpretation of the onedimensional models which are commonly used to interpret experimental kinetic data. 
Thu, Feb 16, '12 
Martin Gradhand, BristolThe spin Hall effect, Berry curvature, impurities, and application After the first experimental observation of the spin Hall effect in semiconductors the topic attracted more and more interest from both experimental and theoretical point of view. The potential of the spin Hall effect to overcome the problem of spin current injection from a ferromagnet into a nonmagnetic material is an important reason for the intensive study of the effect in recent years. I will present my work, methods as well as results, on first principle calculations of the spin Hall effect in metals. This talk focuses on the semiclassical approach where intrinsic and extrinsic mechanisms can be separated naturally. The intrinsic mechanism is governed by the Berry curvature of the pure band structure whereas in the extrinsic case electronimpurity scattering has to be described quantum mechanically. We implemented both contributions where we made use of special features of the applied Greenfunction method and performed broad material scans to identify materials for possible applications. One particular application where the induced spin current is used to switch a ferromagnetic island I will introduce in more detail. Special features of real slabs, more relevant to the experimental situation, will be also discussed. 
Thu, Feb 23, '12 
Rob Smith, CambridgeEffects of interactions on BoseEinstein Condensation 
Thu, Mar 1, '12 
Gavin MorleyQuantum control of electronnuclear spin systems It is technologically simpler to obtain high spin polarization with electrons than nuclei. I use dynamic nuclear polarization at high magnetic fields to transfer polarization from electrons to nuclei. This provides a good starting state for a quantum computation, as well as for NMR experiments. Bismuth atoms in silicon are particularly attractive multiqubit systems because their nuclear spin and electronnuclear coupling are both large. 
Thu, Mar 8, '12 
John Morton, OxfordStoring and manipulating quantum information using electron and nuclear spins in the solid state 
Thu, Mar 15, '12 
Pietro Cicuta, CambridgeDriving potential and noise level determine the synchronization state of hydrodynamically coupled oscillators Driving potential and noise level determine the synchronization state of hydrodynamically coupled oscillators Synchronization has been such a central topic in science over the last 50 years that one wonders whether new breakthroughs are possible. Contrary to this expectation, recent work on cilia and flagella hydrodynamics paints a new ``shade'' of synchronization, with experimental and theoretical evidence supporting the original hypothesis by Taylor in the 50s, that coordinated beating is caused by the interactions through the surrounding fluid. Understanding this physical problem has large biological importance, since cilia and flagella are ubiquitous in eukaryotes, key to the functionality of diverse human tissues, and possibly played a role in the evolution of multicellularity. Central questions are how the internal engine of cilia integrates the cues coming from the fluid in order to achieve (and lose) synchronization with neighbours, and how dynamic states of many oscillators are maintained. Current technology allows to build micronscale active units that exhibit hydrodynamic synchronization, and are simple to describe theoretically, allowing quantitative studies. This talk will present a configurationdependent geometricswitch feedback system, driving colloidal particles with optical traps. We show how the internal force engine with which the active unit pushes the fluid during each beating cycle, i.e. the driving potential, determines the dynamical steady state in competition with thermal noise. In manyoscillator systems, we show how the dynamical state can be predicted on the basis of the equilibrium coupling tensor. 
Thu, May 10, '12 
Cedric Weber, CavendishPS1.28 Dynamical meanfield theory applied to linear scaling density functional theory Interesting properties that are connected to quantum mechanics, such as magnetism, transport, and the effect of impurity atoms and disorder, and their relation to material design and energy needs are important for almost every branch of the industry. Density functional theory (DFT) was successful at making accurate predictions for many materials, in particular compounds which have a metallic behaviour. DFT combines high accuracy and moderate computational cost, but the computational effort of performing calculations with conventional DFT approaches is still non negligible and scales with the cube of the number of atoms. A recent optimised implementation of DFT was however shown to scale linearly with the number of atoms (ONETEP), and opened the route to large scale DFT calculations. Nonetheless, one bottleneck of DFT and ONETEP , is that it fails at describing well some of the compounds where strong correlations are present, in particular because the computational scheme has to capture both the bandlike character of the uncorrelated part of the compound and the Mottlike features emerging from the local strongly correlated centres. A recent progress has been made in this direction by the dynamical meanfield theory (DMFT), that allows to describe the two limits (metal and insulator) in a remarkable precise way when combined with DFT . The ONETEP +DMFT implementation will be shortly discussed, and its applications illustrated by two examples: i) the interplay of Mott and Anderson localization within disordered Vanadium dioxide and ii) a typical biological molecular system, iron porphyrin, which plays an important biological function in human haemoglobin. 
Thu, May 17, '12 
Andrew Green, UCLPS1.28 Quantum orderbydisorder near criticality and the secret of partial order in MnSi The vicinity of quantum phase transitions has proven fertile ground in the search for new quantum phases. We propose a physically motivated and unifying description of phase reconstruction near metallic quantumcritical points using the idea of quantum orderbydisorder. Certain deformations of the Fermi surface associated with the onset of competing order enhance the phase space available for lowenergy, particlehole fluctuations and selfconsistently lower the free energy. Applying the notion of quantum orderbydisorder to the itinerant helimagnet MnSi, we show that near to the quantum critical point, fluctuations lead to an increase of the spiral ordering wave vector and a reorientation away from ?the lattice favored directions. The magnetic ordering pattern in this fluctuationdriven phase is found to be in excellent agreement with the neutron scattering data in the partially ordered phase of MnSi. 
Thu, May 24, '12 
David Logan, OxfordPS1.28 Electronic transport in carbon nanotube quantum dots The talk will focus on aspects of electronic transport in CNT quantum dots  theoretically, but set firmly in an experimental context. Particular emphasis will be given to zerobias transport, and the evolution of conductance as a function of gate voltage, temperature and dotlead tunnel couplings. The symmetrybreaking role of spinorbit coupling will also be discussed; in particular its interplay with the two regimes of SU(4) Kondo physics towards the centres of the Coulomb blockade valleys, which has rather striking implications for experiment. 
Thu, May 31, '12 
Student Seminar DayPS1.28 Sally Bridgwater, Galbadrakh Dagvadorj and Stepan Ruzicka 
Wed, Jun 6, '12 
IoP TCM Group Annual Meeting 2012PLT + Concourse Nigel Cooper, Cambridge, 'Synthetic gauge fields for ultracold atoms'; 
Thu, Oct 11, '12 
Martin Weigel, CoventryPS1.28 Spin glasses with many components 
Thu, Oct 18, '12 
Alastair Kay, OxfordPS1.28 The monogamy of quantum correlations Quantum correlations are monogamous  the more entangled Alice and Bob are, the less entangled Alice can be with anyone else. Indeed, this is the fundamental concept behind most quantum cryptography schemes. However, how do we make such a statement quantitative? One route, which I will describe in the talk, is by understanding quantum cloning better; if you try and copy a quantum state, the better you make one copy, the worse the other copies have to be. I will also describe an important consequence of this monogamy of correlations  how the classical world (technically, local realism) emerges from the quantum one. The talk is based on the following papers: arXiv:1010.2016, arXiv:1208.5574. 
Thu, Oct 25, '12 
Tapash Chakraborty, Antwerp and ManitobaPS1.28 Quantum HallMarks in Monolayer and Bilayer Graphene In this talk, I shall discuss the properties of interacting electrons in monolayer graphene in a strong magnetic field. I shall demonstrate how the effect of the Coulomb interaction differs in a crucial way from that in a conventional twodimensional electron system [PRL 97, 126801 (2006)]. I will also discuss briefly the experimental work reported on the fractional QHE in graphene. In the second half of the talk, I plan to discuss the physics of bilayer graphene in a strong magnetic field. I will explain how the physics of FQHE in this system differs dramatically from that in monolayer graphene and offers unique possibilities to probe the nature of incompressible/compressible states [PRL 105, 036801 (2010)]. I will also discuss (very briefly) the nature of the Pfaffian state in bilayer graphene [PRL 107, 186803 (2011)]. 
Thu, Nov 1, '12 
POSTPONED Jorge Quintanilla, RAL & KentPS1.28 Nonunitary Triplet Paring in the Centrosymmetric Superconductor LaNiGa2 
Wed, Nov 7, '12 
George Rowlands' Big Birthday. A celebration of his work since 'Retirement'PLT Mark Dowsett 'From dress sense to Entropy via a point spread function' Matthew Turner 'There is something fishy about these models' George Rowlands 'Life of a physicist  stage 3' Cake and Champagne on the Concourse Steve Dixon 'Sound Mathematics  Experimental Ultrasonic Results Explained Through Modelling' Nick Watkins (British Antarctic Survey) '50 Shades of George ... and how not to misunderestimate extremes' 
Thu, Nov 15, '12 
Rex Godby, YorkPS1.28 Exact DensityFunctional Potentials for TimeDependent Quasiparticles 
Thu, Nov 22, '12 
Benjamin Beri, CambridgePS1.28 Topological Kondo Effect with Majorana Fermions 
Thu, Nov 29, '12 
Tony Arber, WarwickPS1.28 QEDPlasmas in High Intensity LaserPlasmas 
Thu, Dec 6, '12 
Steven Fitzgerald, CulhamPS1.28 Unstable Dislocations in Anisotropic Crystals 
Fri, Dec 7, '12 
Bohmian mechanics: Exploring AMO Physics with TrajectoriesPS0.17a Prof. Ángel S. Sanz Ortiz, Instituto de Física Fundamental (CSIC), Madrid 
Thu, Jan 24, '13 1pm  2pm 
Mark van Schilfgaarde, KCLPS1.28Quasiparticle Selfconsistent GW Approximation as a Universal Framework for Electronic Structure A new type of selfconsistent scheme within the GW approximation is presented, which we call the quasiparticle selfconsistent GW (QSGW ) approxi mation. It is based on a kind of selfconsistent perturbation theory, where the selfconsistency is used to minimize the difference between the manybody and singleparticle hamiltonians. QSGW describes optical properties in a wide range of materials rather well, including cases where the localdensity and LDAbased GW approximations fail qualitatively. Selfconsistency dramatically improves agreement with experiment, and is sometimes essential. QSGW avoids some formal and practical problems encountered in conventional selfconsistent GW, which will be discussed. It handles both itinerant and correlated electrons on an equal footing, without any ambiguity about how a localized state is defined, or how doublecounting terms should be subtracted. Weakly correlated materials such as Na and sp semiconductors are described with uniformly high accuracy. Discrepancies with experiment are small and systematic, and can be explained in terms of the approximations made. Its consistently high accuracy make QSGW a versatile method that can reliably predict critical energy band properties of graphene, CuInSe2, CaFe2As2 and NiO in a unified framework. Many other properties attendant to the electronic structure can be calculated, such as magnetic excitations, the Auger recombination process, the transmission through a metalsemiconductor contact. In principle it can serve both as a framework to construct effective hamiltonians for manybody physics, and as an engine to build models for device design from first principles, with unprecedented reliability. How to do this in practice is a major challenge today. I will briefly present some discussion of each. 
Thu, Jan 31, '13 1pm  2pm 
Robert Brady, Cambridge Computing LabPS1.28Irrotational solutions to Euler's equation for a compressible fluid This talk is about the patterns of flow in a fluid such as the air if it had no viscosity. It is illustrated with animations and movies, and should be accessible to those without prior knowledge. We show that a compressible inviscid fluid supports structures which are similar to smoke rings, but are irrotational. They obey the same equations of motion and diffraction as natural particles, which is illustrated in movies of an experimental analogue in two dimensions, due to Couder, which show tunnelling, doubleslit diffraction, and quantised energy levels. Some of the structures are chiral. Opposite chiralities attract and like chiralities repel with a force which obeys Maxwell's equations, whose strength is characterised by a fine structure constant less than approximately 1/45. 


Thu, Feb 7, '13 1pm  2pm 
Yong Mao, NottinghamPS1.28Structural Optimisation and Fractal Design Hierarchical design is ubiquitous in nature. Material properties can be tailored by having structural features on many length scales. In our recent work, we demonstrate that through the use of hierarchical, selfsimilar design principles, advantageous structural properties can be obtained. We show that the scaling of the amount of material required for stability against the loading can be altered in a systematic manner. A particular structure is fabricated through rapid prototyping, and we obtain the optimal generation number (for our specific structure) for any given value of loading. 
Mon, Feb 11, '13 2pm  3pm 
Daniele Sanvitto, LeccePLTQuantum Fluids of Polariton Condensates: from fundamental phenomena to polariton logics 
Thu, Feb 14, '13 1pm  2pm 
Fabien Paillusson, CambridgePS1.28Statistical properties of an assembly of vibrated granular systems Akin to what is observed in equilibrium thermodynamics, granular systems display statistical properties because of the huge number of particles they involve. Although athermal, it is thought that some of these properties can be described reliably within an "equilibrium" statistical mechanics framework very similar to that of Gibbs ensembles and called Edwards' statistical mechanics. Focusing on simulations of vibrated granular systems, we will firstly look at an ensemble of them and probe the evolution of their statistics with time. This will allow us to question the type of approach  ensemblist of frequentist  that should be used and compared to Edwards' predictions. This questioning is inevitably related to some formulation of the ergodicity property of the system that we shall then test for our system. Finally, the compatibility with Edwards' framework will be discussed. 
Thu, Feb 21, '13 1pm  2pm 
Jorge Quintanilla, Kent & RALPS1.28Anomalous Nodal Quasiparticles in Superconductors 
Thu, Feb 28, '13 1pm  2pm 
Juan Garrahan, Nottingham POSTPONEDPS1.28Trajectory phase transitions in quantum nonequilibrium 
Thu, Mar 7, '13 1pm  2pm 
Nick Hine, CavendishPS1.28Semiconductor and MetalOxide Nanocrystal Simulations with LinearScaling PAW DFT 
Thu, Mar 14, '13 1pm  2pm 
Andrea Fischer, CambridgePS1.28Superfluid pairing in a quasi2D gas of fermionic atoms 
Thu, May 2, '13 1pm  2pm 
Barry Narod (Narod Geophysics/UBC)PS1.28The origin of noise and of magnetic hysteresis in permalloy ringcore fluxgate sensors 
Wed, May 8, '13 2pm  3pm 
Kristen Fichthorn, Penn StatePS1.28Growth, Transformation, and Assembly of Nanoscale Materials: Insights from Simulation 
Thu, May 9, '13 1pm  2pm 
Sergio Ulloa, FU BerlinPS1.28Magnetoelectric Spin Control in Nanostructures Atomic spinorbit interactions (SOIs) result in interesting dynamical properties on electronic nanostructures. These systems, accessible experimentally on metallic surfaces, semiconducting heterostructures, and carbon nanotubes, to name a few, allow the exploration of symplectic symmetries on a number of measurable quantities. In this talk we will discuss how SOIs result in interesting magnetoelectric effects at the atomic scale when considering adatoms on surfaces. We will describe how quantum corrals made with magnetic atoms allow one to control the spectral properties of quantum systems located inside, via the application of moderate magnetic fields. The unique features of the electronic states in the corral allow for tunableKondo screening effects, among other things [1]. Similarly, we will discuss the ability to control the spin polarization of current (without magnetic fields) through carbon nanotubes wrapped helically with polar molecules, such as DNA [2]. These properties provide powerful alternative tools for probing spintronic properties at the atomic scale. [1] A. T. Ngo, J. RodriguezLaguna, S. E. Ulloa, and E. H. Kim, Nano Letters 12, 13–16 (2012). [2] G. S. Diniz, A. Latge, and S. E. Ulloa, Phys. Rev. Lett. 108, 126601 (2012). 
Thu, May 16, '13 1pm  2pm 
Juan Garrahan, NottinghamPS1.28Trajectory phase transitions in quantum nonequilibrium

Thu, May 23, '13 1pm  2pm 
Gil Rutter and Matthew Bates, WarwickPS1.28 
Thu, May 30, '13 1pm  2pm 
Francesco Gervasio, UCLPS1.28Conformational changes and allosteric control of proteinkinases 
Thu, Jun 6, '13 1pm  2pm 
Alex Rautu & Andrew Goldsborough, WarwickPS1.28Bending Elasticity Measurements for Fluctuating Vesicles (Alex) The mechanical properties of lipid membranes have been extensively studied over the past few decades [1]. Their ability to bend under very low stress is one of the main mechanical properties of such soft materials. This softness is characterised by a very small value of the bending modulus (on the order of 10 kBT). As a result, a flaccid vesicle can attain many thermally allowed shapes at constant volume, which leads the thinwalled vesicles to fluctuate (the socalled flicker phenomenon) [1]. Measurements of these thermal excitations have been used to estimate the bending modulus of red blood cells and artificial vesicles [2][3][4]. Here, we reexamine this methodology and discuss some of its limitations; e.g., videomicroscopy gives only partial information in the sense that it provides a twodimensional view of the threedimensionally fluctuating vesicle. In order to overcome this technical limitation, we develop two new possible methods for inferring mechanical information about membranes from the projected intensity of fluorescent quasispherical vesicles. [1] U. Seifert, Adv. Phys. 46, 13 (1997), [2] J. F. Faucon et al., J. Phys. (Paris) 50, 2389 (1989), [3] J. Pécréaux et al., Eur. Phys. J. E 13, 277 (2004), [4] P. Méléard et al., Eur. Phys. J. E 34, 116 (2011) _______________________________________ The Strong Disorder Renormalisation Group in the age of Tensor Networks (Andrew) We have developed a tensor network method of performing the numerical strong disorder renormalisation group (SDRG) approach [1] to the random 1D spin1/2 Heisenberg model. The numerical SDRG can be reformulated as a randomly branching binary tree tensor network (TTN). This knowledge then enables us to perform a variational update to the network to improve accuracy as well as efficiently calculate expectation values and entanglement entropy. Furthermore, I will discuss how the geometry of the network is related to the physical properties that the network can model. [1] T. Hikihara, A. Furusaki, and M. Sigrist, Phys. Rev. B, vol. 60, p. 12116, 1999. 
Mon, Jul 8, '13 
Computation Meets Experiment: KKR Greens functions for calculations of spectroscopic, transport and magnetic propertiesCS1.04 / PLT (please check website)Runs from Monday, July 08 to Monday, July 15. This will consist of 2 parts: 1) The 'Handson' Computational Tutorial: 8th  12th July 2013 (CS1.04) 2) Research Meeting: 13th  15th July 2013 (PLT) 
Wed, Jul 24, '13 2pm  3pm 
Randy Kamien, UPennP5.23Topology of Soft Materials Soft matter, despite its name, is surprisingly robust. Under broad conditions liquid crystals, colloids, and copolymers assemble into complex, refined structures, often stable over large temperature ranges and capable of selfrepair and healing. Their elasticity is soft and so it is relatively easy to create longwavelength distortions, topological defects, and configurations frustrated by conflicting boundary conditions. I will describe how geometric and topological principles can be applied in these systems to tailor complex, tunable and robust selfassembled arrays of defects and colloids in a variety of liquid crystals, ranging from the hierarchical formation of focal conic domains from patterned micropillar templates, to novel colloidal assemblages built from Janus washers with hybrid boundary conditions.

Thu, Sep 19, '13 1pm  2pm 
Debabrata Panja, UtrechtBacteriophages: fantastic little machines for infecting bacteria 
Thu, Oct 10, '13 1pm  2pm 
Mark Hindmarsh, SussexPS1.28Gravitational waves from phase transitions in the early universe 
Thu, Oct 17, '13 1pm  2pm 
Gareth Conduit, CambridgePS1.28Fewatom approach to manybody physics 
Thu, Oct 24, '13 1pm  2pm 
Vasily Kantsler, WarwickPS1.28Surface interactions in suspensions of swimming cells 
Thu, Oct 31, '13 1pm  2pm 
Sven Dorosz, Luxembourg POSTPONEDPS1.28Fluctuation Relations and Crystallization 
Thu, Nov 7, '13 1pm  2pm 
Sebastiaan Vlaming, DresdenPS1.28Anomalous exciton localization in systems with heavytailed disorder 
Thu, Nov 14, '13 1pm  2pm 
Animesh Datta, OxfordSensing and imaging at the quantum limit 
Thu, Nov 21, '13 1pm  2pm 
Mark Gilbert, CulhamPS1.28Integrated assessment of material performance in a fusion reactor: Neutron transport, transmutation and activation, radiation damage, and helium embrittlement 
Thu, Dec 5, '13 1pm  2pm 
Peter Brommer, WarwickPS1.28From graphene functionalisation to phasechange materials  current and proposed research 
Thu, Jan 9, '14 1pm  2pm 
Mario Cuoco, SalernoSpintriplet superconductors: interface to ferromagnets and magnetic edge states 
Thu, Jan 16, '14 1pm  2pm 
Sven Friedemann, CambridgePS1.28Electronic Structure investigations in Ybbased heavy fermion materials 
Thu, Jan 23, '14 1pm  2pm 
Mark Fromhold, NottinghamPS1.28 
Thu, Jan 30, '14 1pm  2pm 
Timo Betz, CNRS CuriePS1.28Learning from fluctuations: The mechanics of active and passive cellular assemblies 
Thu, Feb 6, '14 1pm  2pm 
Bortolo Mognetti, ULBPS1.28Living Cluster in Suspensions of Active Colloids 
Thu, Feb 13, '14 1pm  2pm 
Alex Chin, Cambridge POSTPONED 
Thu, Mar 6, '14 1pm  2pm 
Gianluca Gregori, OxfordPS1.28Laboratory astrophysics with high power lasers 
Thu, Mar 13, '14 1pm  2pm 
Daniel Burgarth, AberystwythPS1.28Manybody physics from a control perspective 
Thu, Apr 24, '14 1pm  2pm 
Benjamin Trefz, MainzPS1.28Computer Simulations of Active Particles 
Thu, May 8, '14 1pm  2pm 
Jacopo Bertolotti, Exeter 
Thu, May 15, '14 1pm  2pm 
Frank Pinski, CincinnatiPS1.28Theory of Fluctuations in a Thermodynamic System and the Limitations of the OnsagerMachlup Functional 
Thu, May 22, '14 1pm  2pm 
Ahsan Nazir, ManchesterPS1.28Environmental dynamics and the emergence of noncanonical equilibrium states in open quantum systems 
Thu, May 29, '14 1pm  2:30pm 
Anja Humpert, Michael Ambler, Sam BrownPS1.28Modelling of topological defects entangled around nanoparticles of nematic liquid crystal colloids (Anja), Machine Learning for Structure Prediction of NanotubeEncapsulated Crystals (Sam) Calculation of Interfacial Free Energies for TwoPhase Systems via Capillary Waves (Michael) 
Thu, Oct 9,'14 1pm  2:00pm 
vdW EpitaxyPS1.28Series of short presentations on vdW Epitaxy (all welcome). A series of presentations to stimulate discussion on modelling weak epitaxy in van der Waals heterostructures. To include contributions from: Nicholas Hine 
Thu, Oct 16,'14 1pm  2:00pm 
Jiannis Pachos, LeedsPS1.28A useful superconductor: 3D DIII TSC I will present tightbinding models of 3D topological superconductors in class DIII that support a variety of winding numbers. I will show that gapless Majorana surface states emerge at their boundary in agreement with the bulkboundary correspondence. At the presence of a Zeeman field the surface states become gapped and the boundary behaves as a 2D superconductor in class D. Importantly, the 2D and 3D winding numbers are in agreement signifying that the topological order of the boundary is induced by the order of the 3D bulk. Hence, the boundary of a 3D topological superconductor in class DIII can be used for the robust realisation of localised Majorana zero modes. 
Thu, Oct 23,'14 1pm  2:00pm 
Joakim Stenhammar, EdinburghPS1.28Phase behaviour of active Brownian particles Socalled active Brownian particles (ABPs)  i.e., selfpropelled, nonaligning colloids whose swimming direction relaxes through thermal diffusion  constitutes a paradigmatic example of active matter, and can be seen as a minimal model of synthetic swimmers as well as motile bacteria. Recently, simulations of ABPs have demonstrated the existence In this seminar, I will discuss how a semithermodynamic mapping, in the form of a dynamic continuum equation for the timeevolution of the density field, can be derived directly from the microscopic ABP dynamics. A numerical solution of the equations yields quantitative agreement with domain topologies and phaseseparation dynamics (growth 
Thu, Oct 30,'14 1pm  2:00pm 
Myrta Gruening, Queens BelfastPS1.28yambo: An ab initio tool for excited state calculations A detailed description on how electronic systems interact with electromagnetic radiation is the starting point for understanding numerous phenomena in Physics, Chemistry, Biology and for developing new technologies (e.g. photovoltaics cells). Abinitio numerical simulations are increasingly used to support, interpret and guide experimental works. In particular, approaches based on ManyBody perturbation theory such as the GW approximation and the Bethe–Salpeter equation are becoming a standard tool in the calculations of quasiparticle energies (related to direct and inverse photoelectron measurements) and the macroscopic dielectric function (related to e.g optical absorption or electronenergy loss experiments). yambo [1] is an ab initio code for After a quick review of the theoretical approaches I will present the basic features of Yambo as well as some more advanced ones and showcase typical applications. Finally I will give an overview of recent or inprogress developments (e.g. yambo for HPC, realtime implementation, etc...) [1] A. Marini, C. Hogan, M.G. and D. Varsano Comp. Phys. Comm. 180, 1392 (2009) 
Thu, Nov 6,'14 1pm  2:00pm 
Rhoda Hawkins, SheffieldPS1.28Active solids: stress reorganisation and response Initially I will introduce the concept of active matter, that is matter driven out of equilibrium by an internal energy source. In particular I will then focus on active solids. I will present a microscopic model of a disordered viscoelastic active solid, i.e., an active material whose long time behaviour is elastic as opposed to viscous. It is composed of filaments, passive crosslinks, and molecular motors powered by stored chemical energy, e.g., actomyosin powered by ATP. Our model allows us to study the collective behavior of contractile active elements and how their interaction with each other and the passive elastic elements determines the macroscopic mechanical properties of the active material. As a result of the (un)binding dynamics of the active elements, we find that this system provides a highly responsive material with a dynamic mechanical response strongly dependent on the amount of deformation. 
Thu, Nov 13,'14 1pm  2:00pm 
Paola Verrucchi, FirenzePS1.28A description of the measurement process by the parametric representation with environmental coherent states We propose a description of the measurement process based on the parametric representation with environmental coherent states [1], where the environment is the measurement apparatus. Referring to the Von Neumann scheme, we first show that the premeasurement step induces a dynamical evolution for the density of environmental coherent states. The analysis of such evolution allows us to establish a formal relation between the loss of quantum coherence and the distinguishability of the measurement outputs. Moreover, having made use of generalized coherent states for the apparatus, we can consider the consequences of its being macroscopic referring to the relation between classical and largeN limit of a quantum theory, as established by G.Yaffe in Ref.[2]. This finally leads us to a statistical description of the actual production of the output that inherently includes both the probabilistic character of the process, with the Born rule properly recovered, and a symmetry breaking that entails the overall quantum state reduction. [1] Proceedings of the National Academy of Sciences 110, 67486753 (2013) 
Thu, Nov 20,'14 1pm  2:00pm 
Paul Chaikin, NYUPS1.28Diffusion and Organization in Driven Particles Systems 
Thu, Dec 4,'14 1pm  2:00pm 
Bryan Chen, LeidenPS1.28Topological soft matter: from linkages to kinks Networks of rigid bars connected by joints, termed linkages, provide a minimal framework to design robotic arms and mechanical metamaterials built out of folding components. These linkages may admit motions that perform useful functions. Can these motions be made to be topologically robust? I will explain this question and illustrate our answer with a chainlike linkage that, according to linear elasticity, behaves like a topological mechanical insulator whose zeroenergy modes are localized at the edge. Simple experiments we performed using prototypes of the chain vividly illustrate how this edge mode can in fact propagate unobstructed all the way to the opposite end. Indeed, the chain is a mechanical conductor, whose carriers are nonlinear solitary waves, not captured within linear elasticity. This chain can be regarded as the simplest example of a topological mechanical metamaterial whose protected excitations are solitons, moving domain walls between distinct topological mechanical phases. Live demonstrations on real toys will be performed. (Based on work with Nitin Upadhyaya and Vincenzo Vitelli). 
Thu, Jan 15,'15 1pm  2:00pm 
Andrew James, UCLPS1.28Quantum quenches in 2D via arrays of coupled chains Matrix product state (MPS) methods, while highly effective when applied to the study of quantum systems in 1D, stumble in higher dimensions due to the 'area law' growth of entanglement entropy. This growth of entanglement can be mitigated in 2D by studying anistropic systems composed of coupled integrable chains, because the required 'area' is reduced. As a specific example I will describe the implementation of the time evolving block decimation algorithm to study quantum quenches in a system of coupled quantum Ising chains. 
Thu, Jan 22,'15 1pm  2:00pm 
Aleks Reinhardt, CambridgePS1.28Simulating the selfassembly of complex structures Materials that can spontaneously selfassemble have been the subject of extensive recent research. It is possible to achieve a considerable degree of complexity using simple building blocks. For example, using computer simulations, we have found that 2D particles with five regularly arranged 'patches' spontaneously form dodecagonal quasicrystals in certain conditions. But whilst quasicrystals form spontaneously on cooling, it is not necessarily clear that they are also the thermodynamically stable phase. I will present a method to calculate 
Thu, Feb 5,'15 1pm  2:00pm 
James Kermode, WarwickPS1.28Multiscale modelling of materials chemomechanics: from stress corrosion cracking to catastrophic brittle fracture 
Thu, Feb 12,'15 1pm  2:00pm 
Enzo Orlandini, PadovaPS1.28The knotted strands of life Knots are part of our everyday life. In some cases they can be very useful as in climbing or sailing whereas in some others they can be a nuisance, as we experience each time we try to disentangle long extension cables or garden pipes. 
Thu, Feb 19,'15 1pm  2:00pm 
Tim Rogers, BathPS1.28Growthinduced breaking and unbreaking of ergodicity in spin dynamics 
Thu, Mar 5,'15 1pm  2:00pm 
David O'Regan, Trinity DublinFrequencydependent Hubbard U corrections: a viewpoint from densityfunctional theory In contemporary firstprinciples atomistic simulation, the augmentation of approximate density functionals with spatially or energetically localised corrections derived from model Hamiltonians is a common approach to improving their accuracy in more strongly interacting systems. This augmentation may take place on the level of subspaceprojected densitymatrices, as in the widelyused densityfunctional theory + Hubbard U (DFT+U) method, or at the level of subspaceprojected Green's functions, as in DFT + dynamical meanfield theory (DFT+DMFT). In the context of DFT+U, the Hubbard U parameter is usually interpreted either as a measure of the curvature of the totalenergy with respect to subspace occupancies, deemed erroneous and due for cancellation, or as the static limit of the screened Coulomb interaction. In the context of DFT+DMFT, the latter interpretation prevails, but in both cases a generalisation to dynamical, or nonadiabatic interaction parameters U seems admissible. It remains a somewhat open question, however, how essential it is to incorporate dynamical interaction parameters, both in order to match experiment and on fundamental grounds. Here, I will develop a viewpoint from densityfunctional theory, starting from the definition of the Hubbard U as an energy curvature and seeking connections with the dynamical Coulomb interaction computed using the constrained random phase approximation and sometimes used in DFT+DMFT. I will introduce a recentlydeveloped, inexpensive and very simplistic approach to computing model dynamical Hubbard U parameters, dubbed DFT+U(ω), developed to explore these connections. This is based on a readilyavailable combination of static densityfunctional linearresponse theory for the Hubbard U and methods for the dielectric function, such as timedependent densityfunctional theory (TDDFT), in which case we can move beyond the random phase approximation. I will discuss different strategies for solving the resulting nonHamiltonian models, using either a local GW approximation to the selfenergy, for which I will show some preliminary results on SrVO_3, or TDDFT. 
Thu, Apr 30,'15 1pm  2:00pm 
Halim Kusumaatmaja, DurhamPS1.28Exploring the Free Energy Landscapes of Continuum Soft Matter Systems: Minima, Transition States, Pathways In many soft matter systems, the stability of minimum free energy configurations and the transition pathways from one state to another often play a central role. A variety of methods are therefore developed for characterising the free energy landscapes of continuum, Landautype free energy models. Using morphologies of lipid vesicles and a multistable liquid crystal device as examples, I show that the methods allow systematic study of not only the most relevant minimum energy configurations, but also competing transition pathways between any two minima, as well as their corresponding energy barriers and transition state configurations. A global view of the free energy landscapes can therefore be obtained and visualised. Different forms of free energy functionals and boundary conditions can be readily implemented, thus allowing these tools to be utilised for a broad range of problems. 
Thu, May 7,'15 1pm  2:00pm 
Francisco DomínguezAdame, MadridPS1.28Electron transport properties of graphene quantum rings Graphene is a material with a combination of many remarkable properties, in particular, large electron mobility and long spincoherence length. These features spurred the interest in graphene as a material of choice for the design of new electronic devices. In this talk I will review some recent proposals for 
Thu, May 14,'15 1pm  2:00pm 
2nd Year PhD student talksPS1.28Poppy Asman (Warwick)  Modelling dissipative transport in the quantum Hall regime The thermoelectric effect is an interesting phenomenon in physics and is related to the entropy per charge of an excitation. Its study can then lead to the understanding of the statistics of quantum Hall states. I will provide an overview of a model of transport in the quantum Hall regime in terms of an equivalent random resistor network, and some results on the dependence of the total response on the distribution of resistors. I will outline progress on how this model can take account of edge state contributions for the thermoelectric response. David Turban (Cambridge)  Singlet fission in pentacene dimers Singlet fission (SF) is a multi exciton generation process which could be harnessed to improve the efficiency of photovoltaic devices. Recently, fast and efficient SF has been observed in molecular dimers derived from the pentacene molecule. We employ constrained density functional theory to explore the electronic states participating in fission. The SF mechanism is discussed with a focus on symmetry constraints peculiar to the dimer systems under consideration. We find that solventinduced symmetry breaking plays a crucial role in the SF process. 
Thu, May 21,'15 1pm  2:00pm 
Sam Azadi, ImperialPS1.28Metallic solid hydrogen: The "holy grail" of highpressure physics In this talk I’ll present comprehensive results for the highpressure phase diagram of solid hydrogen. 1. Physical Review Letters 112 (16), 165501 (2014) 
Thu, May 28,'15 1pm  2:00pm 
Madan Rao, NCBS IndiaPS1.28Active clustering and implications for information processing on the cell surface There is growing evidence that cells can locally control their membrane composition by active, energyconsuming processes. I will discuss the theory of active clustering of cell surface molecules and its implications for optimisation of information processing. 
Thu, Jun 4,'15 12am  12:00am 
TCM MeetingL4 & Physics ConcoursePROGRAMME: 11:00 Johannes Lischner, Imperial , Theoretical Spectroscopy beyond GW 11:50 Gene Mele, UPenn & Loughborough, Twist and Texture in Multilayer Graphene 13:40 Zoran Hadzibabic, Cambridge, Uniform Bose Gases 14:40 Posters 16:10 Matthew Turner, Warwick, Swarming 
Thu, Oct 15,'15 1pm  2:00pm 
Alberto Rodriguez, FreiburgPS1.28Matterwave scattering from interacting ultracold bosons in optical lattices 
Wed, Oct 21,'15 1pm  2:00pm 
Artem Abanov, Texas A&MPS1.28Joint Condensed Matter and Theory Group seminar 
Thu, Oct 29,'15 1pm  2:00pm 
Nikos Fytas, CoventryPS1.28Universality in disordered systems: the case of the randomfield Ising model 
Thu, Nov 5,'15 1pm  2:00pm 
Alex Rautu, WarwickPS1.28The Role of Optical Projection on Vesicle Fluctuations The optical spectroscopy of thermally induced shape fluctuations of giant unilamellar vesicles (GUVs) has been widely used as a method to extract mechanical information about fluid membranes [1]. Working with the model system of 1,2dioleoylsnglycero3phosphocholine (DOPC) lipids, we reexamine this methodology and discuss how the projection of fluctuations within the focal depth of the microscope may affect the inferred value of the bending modulus (and the surface tension). Within a Gaussian approximation we derive an analytical expression for a mode spectrum that varies with the ratio of the focal depth to the vesicle size. A comparison of our model with the existing approach [24] (that compares experiments with the equatorial fluctuations, without averaging over the focal depth) shows a significant and systematic decrease in the inferred value of the bending modulus. The new procedure is found to be in good agreement with the values measured through Xray scattering and other micromechanical manipulation techniques [5]. [1] U. Seifert, Adv. Phys. 46, 13 (1997) 
Thu, Nov 12,'15 1pm  2:00pm 
Dmitry Kovrizhin, CambridgePS1.28Dynamics of fractionalization in quantum spin liquids I will present the theory of dynamical spin response for the Kitaev honeycomb model, discussing exact results for the structure factor — which shows signatures of spin fractionalization into emergent quasiparticles: Majorana fermions and fluxes of Z2 gauge field — in gapped and gapless, Abelian and nonAbelian quantum spinliquid (QSL) phases. [1] J. Knolle, D.L. Kovrizhin, J.T. Chalker, R. Moessner, Phys. Rev. Lett. 112, 207203 (2014) 
Thu, Nov 19,'15 1pm  2:00pm 
Thomas Swinburne, ImperialPS1.28Using Zwanzig's projection technique to understand the stochastic dynamics of crystal defects The mechanical response and microstructural evolution of a crystal is in large part dictated by the motion of the crystal defects (vacancies, dislocations, impurities) it contains. At finite temperature defect motion is stochastic and viscous due to a strong coupling with thermal phonons, but existing theories based on phonon scattering often show large disagreements with the results from classical atomistic simulations, failing completely for nanoscale defects such as selfinterstitial clusters. We have shown that these failures stem from treating defects and phonons as canonical particles in a harmonic system. In our approach [1], defect motion is a general structural transformation described by an affine parameter isomorphic to the defect position. We have used Zwanzig's projection technique[2] to derive a stochastic equation of motion for the defect with the defectphonon coupling emerging as a GreenKubo relation to the defect force, which can be evaluated statically or dynamically. The form of the friction kernel is closely related to previous microscopic heat bath models. In my talk I will discuss some properties of this new stochastic equation of motion and explain why phonon scattering theories fail to predict the defectphonon coupling. 
Thu, Nov 26,'15 1pm  2:00pm 
Karoline Wiesner, BristolPS1.28The mathematics of information in complex systems A hallmark of complex systems are the presence of order and randomness. The interplay between them allows for robust function. A mathematical framework for uncovering structure and randomness

Thu, Dec 3,'15 1pm  2:00pm 
Brendon Lovett, St AndrewsCoupled quantum systems in structured environments: Master equations and applications to quantumenhanced solar energy harvesting 
Thu, Dec 10,'15 1pm  2:00pm 
Michael Hartmann, Heriot WattPS1.28Strongly Interacting Photons: Coherence, Correlations and Propagation Light consists of photons, massless particles that do not interact with one another. Recent technological developments however give rise to structures with strong interactions between light and matter in multiple nodes of a network. These devices may enable us to drive photons into novel strongly correlated quantum manybody regimes. Interestingly, these may by studied in nonequilibrium scenarios where inevitable photon losses are constantly compensated by input drives. They thus give rise to an intriguing class of quantum manybody systems where instead of ground or thermal states one is interested in the still largely unexplored stationary states of their driven and dissipative dynamics. In this talk, I will present some of our recent approaches to this physics that explore photonphoton correlations in chains of nonlinear resonators with coherent or incoherent pumping. 1) J. RuizRivas, E. del Valle, C. Gies, P. Gartner, and M. J. Hartmann, Spontaneous, collective coherence in driven, dissipative cavity arrays, Phys. Rev. A 90, 033808 (2014). 
Thu, Jan 21,'16 1pm  2:00pm 
Hugues Chate, CEAPS1.28Active matter: An introduction and some recent advances 
Thu, Jan 28,'16 1pm  2:00pm 
Keith McKenna, YorkPS1.28Understanding defects in metaloxide materials 
Thu, Feb 11,'16 1pm  2:00pm 
Erik Gauger, Heriot WattPS1.28Flow of information and energy in quantum networks 
Thu, Feb 18,'16 1pm  2:00pm 
Francesco Ginelli, AberdeenPS1.28Leading birds by the beak: On the response of flocks to external perturbations 
Thu, Feb 25,'16 1pm  2:00pm 
Tyler Shendruk, OxfordPS1.28A Mesoscopic Particlebased Method for Nematohydrodynamics Research on topological microfluidic transport, the dynamics of selfassembly in liquid crystals and socalled hypercomplex fluids requires versatile and numerically efficient mesoscopic algorithms. I will describe a multiparticle collision dynamics (MPCD) based algorithm for simulating fluctuating nematohydrodynamics, the flow of liquid crystals. This nematicMPCD method successfully reproduces the features of a nematic liquid crystal, including an isotropicnematic phase transition, intrinsic elastic coefficients, tumbling and shear alignment regimes, and defect dynamics. Though simple, it represents a promising tool for modelling defect dynamics within porous media, the interactions of colloids, selfpropelled particles and dispersed carbon fibres within liquid crystal media. I demonstrate of the method can be extended to simulate active fluids, which represent an exciting path for studying intrinsically outofequilibrium phenomena with direct ramifications for biological systems. Active MPCD simulations exhibit the hallmarks of active nematic fluids, including the formation of lines of kinks in the orientation field and the onset of mesoscale trubulence via the unzipping of these lines through the creation of topological defects. 
Thu, Mar 10,'16 1pm  2:00pm 
Gerardo Adesso, NottinghamPS1.28Robustness of coherence: An operational and observable measure of quantum coherence 
Thu, Mar 17,'16 1pm  2:00pm 
Antonio GarciaGarcia, CambridgePS1.28Smaller is different and more: Low dimensional superconductivity for new physics and applications 
Thu, May 5,'16 1pm  2:00pm 
Edgar Engel, CambridgePS1.28Calculating anharmonic vibrational properties of water ice 
Thu, May 12,'16 1pm  2:00pm 
Aires Ferreira, YorkPS1.28Critical delocalization of chiral zero energy modes in disordered graphene 
Thu, May 19,'16 1pm  2:00pm 
2nd Year PhD student talks IPS1.28Antonino Savojardo & Edoardo Carnio Antonino Savojardo  Rogue wave generation due to inelastic quasisoliton collisions in optical fibres Edoardo Carnio  Ab initio metalinsulator transition in doped silicon 
Thu, May 26,'16 1pm  2:00pm 
2nd Year PhD student talks II + Chris PatrickPS1.28Eduardo MendiveTapia & Chris Patrick Eduardo MendiveTapia  Fourion Magnetic Coupling in the Heavy Rare Earth Elements

Wed, Jun 1,'16 12am  12:00am 
TCM MeetingL3, Physics ConcoursePROGRAMME: 11:00 HaiQing Lin, Beijing 11:50 Sania Jevtik, Imperial, Disentangling entangled quantum states 13:40 Mike Cates, Cambridge, What is the pressure of an active suspension? 14:40 Posters 16:10 Hannah Price, Trento, Synthetic Gauge Fields in Synthetic Dimensions with Ultracold Atoms and Integrated Photonics 
Thu, Oct 13,'16 1pm  2:00pm 
Theory Seminar: PierEmmanuel Tremblay (Warwick)PS1.283D Model Atmospheres of White Dwarfs 
Thu, Oct 20,'16 1pm  2:00pm 
Theory Seminar: Alexander Taylor (Bristol)PS1.28Geometry and topology of vortices in random quantum eigenfunctions Disordered complex 3D scalar wave fields typically contain a dense tangle of nodal lines (quantized vortices), which are important in diverse physical wave systems including turbulent superfluids, optical volume speckle, the quantum eigenfunctions of chaotic 3D cavities, and liquid crystal phases. Based on extensive numerical simulations these nodal tangles are known to have fractal properties on large scales, although more subtle topological quantities such as the probability of knotted or linked vortices are sensitive to the details of the model. We numerically generate many examples of wave chaos in three random systems at fixed energy (3D cube with periodic boundary conditions, 3sphere and 3D harmonic oscillator), analysing aspects of their statistical geometry and identifying the knot types of the vortex curves which appear. Knots tend to occur with high probability even at comparatively low energies, and the statistics of knot complexity vary significantly amongst the three systems. Furthermore, the different symmetries and boundary conditions of these systems strongly affect the knotted conformations that can occur, and we discuss how this relates to the statistics of knotting with mode count in different systems. 
Thu, Oct 27,'16 1pm  2:00pm 
Theory Seminar: Simon Connell (Leeds)PS1.28TBA 
Thu, Nov 3,'16 1pm  2:00pm 
Theory Seminar: Haixing Miao (Birmingham)PS1.28Quantum limits of laser interferometric gravitationalwave detectors Current groundbased gravitationalwave detectors, e.g., Advanced LIGO, are kilometre scale Michelsontype laser interferometers with kilogram mirrorendowed test masses. Even though they are macroscopic in size, quantum mechanics plays an important role in determining their sensitivity. In particular, quantum fluctuation of the optical field not only sets the measurement imprecision in terms of shot noise, but also induces quantum back action noise that perturbs the motion of test masses. The tradeoff between these two types of quantum noise gives rise to the socalled Standard Quantum Limit (SQL). For the first part of this talk, we will walk through different approaches to surpassing the SQL, which leads to a more stringent sensitivity limitthe Fundamental Quantum Limit (FQL). For the second part, we will present current understanding of the FQL and its implications for enhancing detector sensitivity. The discussions here are not limited to gravitationalwave detectors, and can be applied to general linear quantum measurement devices. References: arXiv:1305.3957 for the first part and arXiv:1608.00766 for the second. 
Thu, Nov 10,'16 1pm  2:00pm 
Theory Seminar: Yutaka Shikano (Institute for Molecular Science, Japan)PS1.28Observation of AharonovBohm effect with quantum tunneling Quantum tunneling is one such phenomenon that is essential for a number of devices that are now taken for granted. However, our understanding of quantum tunneling dynamics is far from complete, and there are still a number of theoretical and experimental challenges. The dynamics of the quantum tunneling process can be investigated if we can create a large tunneling region. We have achieved this using a linear Paul trap and a quantum tunneling rotor, which has resulted in the successful observation of the Aharonov–Bohm effect in tunneling particles. Also, this result shows that the spatially separated phonon can be interfered. This work is collaborated with Atshushi Noguchi, Kenji Toyoda, and Shinji Urabe. Nature Communications 5, 3868 (2014) 
Thu, Nov 17,'16 1pm  2:00pm 
Theory Seminar: Johannes Knolle (Cambridge)PS1.28Quantum oscillations without a Fermi surface and the anomalous de Haasvan Alphen effect The de Haasvan Alphen effect (dHvAe), describing oscillations of the magnetization as a function of magnetic field, is commonly assumed to be a definite sign for the presence of a Fermi surface (FS). Indeed, the effect forms the basis of a wellestablished experimental procedure for accurately measuring FS topology and geometry of metallic systems, with parameters commonly extracted by fitting to the LifshitzKosevich (LK) theory based on Fermi liquid theory. Here we show that, in contrast to this canonical situation, there can be quantum oscillations even for band insulators of certain types. We provide simple analytic formulas describing the temperature dependence of the quantum oscillations in this setting, showing strong deviations from LK theory. We draw connections to recent experiments an SmB6. 
Thu, Nov 24,'16 1pm  2:00pm 
Theory Seminar: Ivan Coluzza (Vienna): Design of patchy polymers: biomimetic selfknotting chainsPS1.28We present a novel theoretical framework within which we are able to design new experimentally realisable materials with tuneable selfassembling properties. Our work takes inspiration from the results obtained with our recently developed protein coarse graining procedure, namely the “Caterpillar” model [1,2]. Based on these results we postulated the “minimum valence principle" (MVP). According to the MVP in order for a generalised beadspring system to be designable and foldable, it is sufficient for the chain to have a sequence of different isotropic interactions combined with directional interactions that further constrain the configurational space. Based on this principle we introduced an optimal set of modular subunits, and the definition of a design procedure necessary to choose a string of the units that once bonded into a chain will spontaneously fold to a specific target structure [35]. We show that such structures can be highly nonsymmetrical and posses interesting topological properties fully controllable by the sequence of beads along the chain. Biomimetic patchy polymers represent a considerable step forward in the synthesis of novel materials, because they are based on a limited alphabet of particles that can be reused and assembled, practically, in an infinite number of combinations. Artificial modular self assembling systems such as this one are not available at the moment and the one we propose is the first of this kind. [1] Coluzza, I. (2011). A coarsegrained approach to protein design: learning from design to understand folding. PloS one, 6(7), e20853. doi:10.1371/journal.pone.0020853 [2] Coluzza, I. (2013). Transferable coarsegrained potential for de novo protein folding and design. Submitted. [3] Coluzza, I., & Dellago, C. (2012). The configurational space of colloidal patchy polymers with heterogeneous sequences. Journal of Physics: Condensed Matter, 24(28), 284111. doi:10.1088/09538984/24/28/284111 [4] Coluzza, I., van Oostrum, P. D. J., Capone, B., Reimhult, E., & Dellago, C. (2012). Design and folding of colloidal patchy polymers. Soft Matter. doi:10.1039/c2sm26967h [5] Coluzza, I., van Oostrum, P. D. J., Capone, B., Reimhult, E., & Dellago, C. (2013). Sequence Controlled SelfKnotting Colloidal Patchy Polymers. Physical Review Letters, 110(7), 075501. doi:10.1103/PhysRevLett.110.075501 
Thu, Dec 1,'16 1pm  2:00pm 
Theory Seminar: Stephen Clark (Bath)  "Enhanced superexchange pairing in a periodically driven Hubbard model"PS1.28Controlling the structural and electronic properties of solids with THz lasers has opened up tantalizing prospect in ultrafast materials science. In contrast to optical frequencies it enables modeselective driving of vibrational excitations relevant for the establishment of various brokensymmetry states. In particular socalled lightinduced superconductivity has been observed in several materials ranging from cuprates to alkalidoped fullerenes. Motivated by experiments on driven infrared active molecular vibrations in organic materials, I will discuss the effect of a finite frequency ω modulation of onsite energies in the Hubbard model with a checkerboard spatial periodicity. In particular we focus on the strongcoupling limit U >> t of the doped Hubbard model where the effective tJ Hamiltonian is applicable and superexchange pairing can occur. Through a Floquet analysis, in the physically relevant regime where U >> ω and ω >> t, J, we show that this driving causes a substantial suppression of the electronic hopping t, while leaving the bare superexchange interaction J unchanged. This suggests that electrons can be slowed down enough in the outofequilibrium state to allow the normally subordinate superexchange interaction to become dominant, and thus favour nearestneighbour pairing. I will show that this leads to a compelling new pathway to engineering lightinduced superconductivity in strongly correlated quantum materials. 
Thu, Dec 8,'16 1pm  2:00pm 
Theory Seminar: Arijeet Pal (Oxford): Many body localisation: one, two, three,…, infinityPS1.28Equilibrium statistical physics holds true for an ergodic system which loses all local information of its initial condition under time evolution. In the last decade, a flurry of theoretical work has shown that ergodicity can be broken in an isolated, quantum manybody system even at high energies in the presence of disorder, a phenomena known as manybody localisation (MBL). The recent experimental observation of MBL in ultracold atoms has raised a plethora of intriguing questions. In this talk I will throw some light on the effect of dimensionality on the properties of MBL. In one dimension, the strongly localized regime is described in terms of quasilocal integrals of motion, also known as lbits. Based on this picture we develop an efficient tensor network method to evaluate the entire spectrum of fully manybody localised systems. I will also present the nonergodic properties of eigenstates of infinite range quantum spin glass models governed by localisation on the infinite dimensional hypercube. On going away from the limiting cases of one and infinite dimensions, I will develop a refined phenomenology of MBL in terms of l*bits which are only approximately conserved and discuss their experimental consequences. 
Thu, Jan 19,'17 1pm  2:00pm 
Theory Seminar: Zlatko Papic (Leeds): Quantum integrability from the entanglement spectrumPS1.28Quantum manybody systems are challenging to study because of their exponentially large Hilbert spaces, but at the same time they represent an arena for exciting new physics which results from interactions between particles. For theoretical purposes, it is convenient to know if such systems can be expressed in a "simple" ways in terms of some nearlyfree quasiparticles, or more generally if one can construct a large set of operators that approximately commute with the system’s Hamiltonian. In this talk I will discuss two ways of approaching these questions using the "entanglement spectrum". In the first part, I will show that strongly disordered systems in the manybody localized phase have a universal powerlaw structure in their entanglement spectra. This is a consequence of their local integrability, and distinguishes such states from typical ground states of gapped systems. In the second part, I will introduce a notion of “interaction distance” and show that the entanglement spectrum can be used to quantify “how far” an interacting ground state is from a free (Gaussian) state. I will discuss some examples of quantum spin chains and outline a few future directions. [1] M. Serbyn, A. Michailidis, D. Abanin, Z. Papic, arXiv:1605.05737. [2] C. J. Turner, K. Meichanetzidis, Z. Papic, and J. K. Pachos, arXiv:1607.02679. 
Thu, Feb 23,'17 1pm  2:00pm 
Theoretical Physics Seminar: Dave Foster (Bristol), Skyrmions and Nuclear StatesPS1.28The Skyrme model is a nonlinear model of nuclear physics, which can be derived from fundamental physics. Its topological excitations model nuclei and are called Skyrmions. In this talk I shall introduce the Skyrme model, and a piece of research where we modelled key nuclei states as spinning Skyrmions (Nuclear Physics B 899 (2015) 513–526). 
Thu, Mar 2,'17 1pm  2:00pm 
Theoretical Physics Seminar: Neophytos Neophytou (Warwick), Understanding and designing the thermoelectric properties of nanomaterials using atomistic and quantum transport simulationsPS1.28tba 
Thu, Mar 9,'17 1pm  2:00pm 
Theoretical Physics Seminar: Mark Howard (Sheffield), Application of a resource theory for magic states to faulttolerant quantum computingPS1.28Motivated by their necessity for most faulttolerant quantum computation schemes, we formulate a resource theory for magic states. We first show that robustness of magic is a wellbehaved magic monotone that operationally quantifies the classical simulation overhead for a GottesmanKnill type scheme using ancillary magic states. Our framework subsequently finds immediate application in the task of synthesizing nonClifford gates using magic states. When magic states are interspersed with Clifford gates, Pauli measurements and stabilizer ancillas  the most general synthesis scenario  then the class of synthesizable unitaries is hard to characterize. Our techniques can place nontrivial lower bounds on the number of magic states required for implementing a given target unitary. Guided by these results we have found new and optimal examples of such synthesis. [arXiv: 1609.07488] 
Thu, Mar 16,'17 1pm  2:00pm 
Theoretical Physics Seminar: Patrick Warren (Unilever), The AmontonsCoulomb percolation transition: how a staple yarn transmits tension and why our clothes don't fall apartPS1.28In his celebrated 1638 Dialogues Concerning Two New Sciences, Galileo identified a fascinating problem in the mechanics of ropes. His fictitious discussant Salviati asks "How are fibres, each not more than two or three cubits in length, so tightly bound together in the case of a rope one hundred cubits long that great force is required to break it?" He then proceeds to explain that " [...] in the case of the rope the very act of twisting causes the threads to bind one another in such a way that when the rope is stretched with a great force the fibres break rather than separate from each other." With the benefit of hindsight, one might say Galileo recognized that the mechanical integrity of ropes (and by implication staple yarns and woven fabrics) is down to frictional contacts between fibres. But beyond this general observation, and despite our everyday familiarity with these issues, one can argue that Galileo's physics problem has remained unresolved for nearly four hundred years. Here it is proposed that the mechanical integrity of such fibre assemblies is actually a consequence of a generic tensile stress percolation transition, which appears under the AmontonsCoulomb friction laws for long enough fibres and with enough entanglement. This is demonstrated in abstract yarn models in which the friction laws are formulated as a linear programming (LP) problem. In these models the percolation transition is manifest as the onset of LP feasibility, wherein the yarn can in principle support an unbounded tensile load without slippage even though the fibre ends remain tensionfree. 
Thu, May 25,'17 1pm  2:00pm 
Theory Seminar: 2nd year PhD talks, Christopher Lakey and Oliver Dyer, 1300 in PS1.28PS1.28Oliver Dyer: An introduction to Wavelet Monte Carlo dynamics The inclusion of longrange hydrodynamic interactions (HIs) in simulations of softmatter systems leads to large computational costs that make the simulation of large systems impractical, motivating the search for more efficient algorithms. In this talk I introduce Wavelet Monte Carlo dynamics (WMCD), a new algorithm that includes hydrodynamics in the distributions of Monte Carlo moves such that a WMCD code does not need to calculate HIs explicitly. Together with an overview of the algorithm itself, I present results showing how WMCD compares to established algorithms and confirming its validity as a hydrodynamic simulator. 
Thu, Jun 1,'17 1pm  2:00pm 
Theory Seminar: Elisabetta Matsumoto (Georgia Tech), NonEuclidean Virtual Reality, 1300 in PS1.28 (joint with the Geometric Topology seminar)PS1.28The properties of euclidean space seem natural and obvious to us, to the point that it took mathematicians over two thousand years to see an alternative to Euclid’s parallel postulate. The eventual discovery of hyperbolic geometry in the 19th century shook our assumptions, revealing just how strongly our native experience of the world blinded us from consistent alternatives, even in a field that many see as purely theoretical. Noneuclidean spaces are still seen as unintuitive and exotic, but with direct immersive experiences we can get a better intuitive feel for them. The latest wave of virtual reality hardware, in particular the HTC Vive, tracks both the orientation and the position of the headset within a roomsized volume, allowing for such an experience. We use this nacent technology to explore the threedimensional geometries of the Thurston/Perelman geometrization theorem. This talk focuses on our simulations of H³ and H²×E. Joint work with: Vi Hart, Andrea Hawksley, and Henry Segerman 
Tue, Jun 6,'17 12am  12:00am 
TCM MeetingL3, Chemistry ConcoursePROGRAM 11:00 Rebecca Nicholls, Oxford, Enhancing Materials Design 11:50 Nicholas Bristowe, Kent, Magnetoelectric Ferroics 13:40 Tapio AlaNissila, Loughborough, Polymer Driven Translocation 14:30 Posters 16:10 Andrew James, UCL, 2D ManyBody Systems 
Thu, Jun 8,'17 1pm  2:00pm 
Theory Seminar: 2nd year PhD talks, Dominic Branford and Nelson Yeung, 1300 in PS1.28PS1.28TBA 
Thu, Jun 15,'17 1pm  2:00pm 
Theory Seminar: Buddhapriya Chakrabarti (Sheffield), A tale of two problems: surface segregation in polymer mixtures, and selfassembly of orientable objects on curved flexible manifolds, 1300 in PS1.28PS1.28I shall be describing two of my current interests in soft matter, small molecule migration in complex matrices and shape minimisation of assembled liquid crystals (that break orientational order) on curved flexible manifolds with free boundaries and edges. The first problem arises in several products of daily use and lead to reduced functional properties, Controlling surface segregation therefore can lead to design of products with well tailored properties. Fundamental polymer physics issues arising in this context will be addressed and a new phenomenological free energy functional that incorporates elastic degrees of freedom in surface segregating systems of gels discussed. Next I will discuss a variational formulation that we have developed for simultaneously minimising elastic free energy and shape for liquid crystals on flexible surfaces. Frustration arising in curved geometries naturally leads to the formation of defects. Our formulation allows us to correctly evaluate and predict the existence of a defect phase that is a mixture of a disclination and a screw dislocation in a class of Smectics. Earlier attempts at obtaining the shape equations in systems having shapeorientational order coupling have been erroneous. 
Thu, Oct 5,'17 1pm  2:00pm 
Theory Seminar: John Molina (Kyoto), Dynamics of Active Particles: From swimmers to crawling cells, 1300 in PS1.28PS1.28Active systems, composed of “particles” that consume local energy to perform work, have attracted a great deal of attention due to their relevance in Physics, Biology, Medicine, and Engineering. Examples of these systems can be found at vastly different length scales: from the nanoscale, with kinesin motors transporting cargo inside of cells, to the microscales of cells crawling around to close wounds or bacteria swimming in viscous media, and finally, to the macroscales at which fish, birds, and humans move about. In our work, we have focused on studying the dynamics of micrometer sized active particles, including both swimmers (e.g., bacteria) and crawlers (e.g., epidermal cells). While we have a fairly complete understanding of the propulsion mechanism used by such particles, the nontrivial coupling between the particle and its environment gives rise to complex dynamical behaviors that have yet to be fully explained. In other words, we know how a single bacteria or cell is able to move, but we cannot always predict what will happen when many of these particles come together. Given the difficulty of performing controlled experiments on these type of systems, computer simulations have become one of the preferred approaches for studying the properties of these active systems. We will introduce the basic computational models that allow us to study the dynamics of interacting swimmers, including the full hydrodynamic interactions, as well as the collective motion of crawling cells on 2D substrates. In the first part of the presentation, we will discuss the collective motion of particles swimming in a viscous medium. We will show that the type of swimming, determined by whether the propulsion is generated at the front (e.g., a puller like the Chlamydomonas algae) or at the back (e..g,, a pusher such as spermatozoids or most bacteria), has a crucial effect on the hydrodynamic interactions between swimmers, and thus, on the collective motion that can be observed[14]. In the second part of our talk, we will consider the dynamics of cells crawling on 2D substrates. Here, we will focus on the response of the cell to a periodic stretching of the substrate, which is known to result in a preferential alignment that is cell specific[5], and on the role of cellcell interactions on the large scale collective motion of cell colonies[6]. References: [1] Molina, Nakayama, and Yamamoto, Soft Matter 9, 4923 (2013) [2] Molina and Yamamoto, Mol. Phys. 112, 1389 (2014) [3] Oyama, Molina, and Yamamoto, Phys. Rev. E 93, 043114 (2016) [4] Delfau, Molina, and Sano, Europhys. Lett. 114, 24001 (2016) [5] Okimura, Ueda, Sakumura, and Iwadate, Cell Adhes. Migr. 0, 1 (2016) [6] Schnyder, Molina, Tanaka, and Yamamoto, Sci. Rep. 7, 5163 (2017) 
Thu, Oct 12,'17 1pm  2:00pm 
Theory Seminar: David Jennings (Oxford), Thermodynamics, symmetry principles and quantum information, 1300 in PS1.28PS1.28The concept of irreversibility lies at the heart of physics and can often be a subtle thing to pin down. In recent years it has acquired new guises that are motivated by informationtheoretic aims. For example in the case of quantum entanglement, intrinsically nonclassical correlations may be utilised to achieve tasks such as quantum teleportation or quantum computing. However, the use of this entanglement results in its consumption, and a form of irreversibility that can be quantified and studied in a precise manner. Here I will describe recent work that arises from both the study of entanglement and also the development of symmetry principles beyond Noether's theorem. The approach allows us to extend thermodynamic concepts into arbitrarily nonclassical regimes and leads to a range of new insights: it shows that quantum systems display a form of disorder at the nanoscale very different from that at macroscopic scales; it allows us to rigorously quantify the effects of quantum coherence in thermodynamic processes; it also provides a quantum information toolkit to extend gauge symmetries in manybody physics beyond Lagrangian formulations. The discussion will be an introduction to these concepts, and so no specialist knowledge of the area is assumed. 
Thu, Oct 19,'17 1pm  2:00pm 
Theory Seminar: Alex Chin, tba, 1300 in PS1.28PS1.28tba 
Thu, Nov 2,'17 1pm  2:00pm 
Theory Seminar: AnaSuncana Smith (Erlangen), From membranes, to tissues, to active motion, 1300 in PS1.28PS1.28Membranes are ubiquitous in living cells but many questions remain outstanding. These include how to characterize a membrane's material properties and their interactions with the environment. Living membranes are generically out of equilibrium and I will discuss how active fluctutations may be involved in the control of the formation of protein assemblies. These structures have important implications on the organization of cells within tissues and the control of their shape. I will outline basic physical principles which may contribute used to understand the epithelium. In the last part of the talk, I will outline the role of elasticity in the behavior of active swimmers, from a single entity to a swarm. 
Thu, Nov 9,'17 1pm  2:00pm 
Theory Seminar: Ognyan Oreshkov (Oxford/Bruxelles), Indefinite causal order in quantum mechanics, 1300 in PS1.28PS1.28According to quantum theory, physical variables in general do not have definite values unless measured. Yet, the time and causal order of events are assumed definite. A natural question is whether the latter reflects a fundamental physical restriction or it is an artefact of our formulation of the theory. Is it possible that, in suitable circumstance, the causal order of events can be indefinite similarly to other physical variables, how would this be described formally, and what testable consequences would it entail. To investigate these questions, we recently introduced a theoretical framework for correlations between separate quantum experiments that does not assume a causal structure from the outset, but only the validity of standard quantum theory locally. This framework unifies all correlations between local quantum experiments in spacetime via a mathematical object called the ‘process matrix’, which generalises the standard density matrix. Remarkably, the framework also reveals the inprinciple possibility for a new kind of correlations incompatible with any definite causal structure. In this talk, I review these results and discuss recent progress in understanding whether such acausal scenarios could have a physical realisation within standard quantum mechanics. 
Thu, Nov 16,'17 1pm  2:00pm 
Theory Seminar: Sergii Strelchuk (Cambridge), Optimal Portbased Teleportation in Arbitrary Dimension, 1300 in PS1.28PS1.28Quantum teleportation is one of the earliest and most widely used primitives in Quantum Information Science which performs an arbitrary quantum state transfer between two spatially separated systems. It involves presharing an entangled resource state and consists of three simple stages. The first stage involves a joint measurement of the teleported subsystem together with the share of the resource state on the sender’s side. In the second step, a classical measurement outcome is communicated to the receiver. The last step consists of applying a requisite correction operation which recovers the transmitted quantum state. Portbased teleportation (PBT) is a unique set of teleportation protocols in that they do not require unitary correction. We study PBT protocols and fully characterize their performance for an arbitrary dimensions and number of ports. We find optimal probability of success and the fidelity of teleportation for all probabilistic and deterministic PBT schemes. In the latter case, surprisingly, the answer depends only on a largest eigenvalue of a certain easy to construct matrix which encodes the relationship between a set of Young diagrams and emerges as the the optimal solution to the relevant semidefinite program. To derive our results, we develop new mathematical tools to study the symmetries of the operators that arise in PBT protocols and belong to the algebra of partially transposed permutation operators. These tools can be used to characterize quantum systems with partial symmetries. Quantum states occurring in the PBT protocol are one such example. Systems with partial symmetries are widespread but in contrast to their permutationalinvariant counterparts very little is known about how to efficiently estimate their properties. 
Thu, Nov 23,'17 1pm  2:00pm 
Theory Seminar: Elsen Tjhung (Cambridge), Time reversal symmetry breaking in scalar field theory, 1300 in PS1.28PS1.28Active matter is a class of nonequilibrium systems where energy is injected to the system continuously by the constituent particles themselves. Many examples of active matter are biological in nature, for example, bird flocks, bacterial suspensions and biological tissues. In the case of bacterial suspensions, the fluid solvent is continuously stirred by the swimming motion of the bacteria, driving it outofequilibrium. Active matter is an interesting class of nonequilibrium systems because it often displays largescale time reversal symmetry breakdown at steady state. For example, when we put an asymmetric gear into a bath full of bacteria, the gear will start to rotate in one direction at steady state. This is a manifestation of largescale time reversal symmetry breaking because if we reverse the arrow of time, the gear will rotate in the other direction. In this talk, I will present a simple scalar field theory which can capture such largescale time reversal symmetry breaking. 
Thu, Nov 30,'17 1pm  2:00pm 
Theory Seminar: Stephen Powell (Nottingham), Nonequilibrium classical dynamics and quantum phases of dimer models, 1300 in PS1.28PS1.28Dimer models arise as effective descriptions in a variety of physical contexts, and provide paradigmatic examples of systems subject to strong local constraints. Their statistical mechanics exhibits unusual phenomena such as algebraic correlations and deconfinement of monomer excitations. I will first describe the classical nonequilibrium dynamics of the dimer model, where signatures of strong correlations are visible in both global and local observables, and can be understood in terms of onedimensional strings of high mobility. I will then show how the classical dynamics can be used to study the corresponding quantum problem, and helps to resolve an outstanding puzzle about the structure of the phase diagram. 
Thu, Dec 7,'17 1pm  2:00pm 
Theory Seminar: Paul Goddard (Warwick), Determining the Fermi surface of hightemperature superconductors and other lowdimensional materials, 1300 in PS1.28PS1.28I will discuss recent magnetotransport data on an underdoped hightemperature superconductor. To assist with the discussion I will first describe how one goes about mapping the Fermi surface of quasitwodimensional materials using high magnetic field measurements, focussing particularly on the technique of angledependent magnetoresistance. This will be illustrated using the results of earlier experiments on an organic superconductor, for which a full determination of the Fermi surface was possible. I then will contrast this with the more challenging measurements performed on YBa2Cu3O6+x and explain what conclusions can be drawn in this case. 
Thu, Jan 11, '18 1pm  2:00pm 
Theory Seminar: Mark Ancliffe (Catholic University of Korea) 
Thu, Jan 18, '18 1pm  2:00pm

Hua Guo (University of New Mexico) 
Thu, Jan 25, '18 1pm  2:00pm

Antonio Rodriguez (Universidad Politécnica de Madrid) 
Thu, Mar 1, '18 1pm  2:00pm 
Leonardo Banchi (Imperial) 
Thu, Mar 8, '18 1pm  2:00pm

Frank Schlawin (Oxford) 
Thu, Mar 15, '18 1pm  2:00pm

Laura Filion (Utrecht) 
Thu, May 3, '18 1pm  2:00pm

Angelika Knothe (Manchester) 
Thu, May 10, '18 1pm  2:00pm 
Rodrigo Lima (Universidade Federal de Alagoas) 
Thu, May 17, '18 1pm  2:00pm 
Graeme Henkelman (Utexas) 
Thu, May 31, '18 1pm  2:00pm 
Thomas Ouldridge (Imperial) 
Thu, June 8, '18 1pm  2:00pm 
Sebatrata Mukherjee (HeriotWatt) 
Thu, Oct 4,'18

Theory Seminar: Mark Dennis (Birmingham), Scientific Properties Of Complex KnotsPS1.28tba 
Thu, Oct 11,'18

Theory Seminar: Thomas Machon (Bristol), Topology and broken translational symmetry: two liquid crystalline case studies and some general resultsPS1.28We study the topology of smectic defects in two and three dimensions. We give a topological classification of smectic point defects and disclination lines in three dimensions. In addition we describe the combination rules for smectic point defects in two and three dimensions, showing how the broken translational symmetry of the smectic confers a path dependence on the result of defect addition. 
Thu, Oct 25,'18

Theory Seminar: John Biggins (Cambridge), Large strain elasticity: geometry, instability and brainsPS1.28We are all familiar with the prototypical elastic instability: the buckling of a slender column under a compressive load. Soft elastic solids, such as rubbers, gels, and biological tissues, are united by their ability to sustain very large shape changes, and consequently undergo a range of more exotic elastic instabilities underpinned by the nonlinear geometry of large strains. I will discuss several such instabilities, including fingering in soft solid layers under tension, beading in solid cylinders subject to surface tension, and a brand new "peristaltic" instability in inflated cylindrical channels. In the second half of the talk, I will discuss the buckling of a growing layer adhered to a soft substrate. I will argue on symmetry grounds that such buckling will inevitably produce patterns of hexagonal dents near threshold, and then make a biological case that this buckling process leads to the folded shape of the human brain. 
Thu, Nov 1,'18

Theory Seminar: Shigeyuki Komura (Tokyo), A threesphere microswimmer in a structured fluidPS1.28We discuss the locomotion of a threesphere microswimmer in a viscoelastic structured fluid characterized by typical length and time scales [1]. We derive a general expression to link the average swimming velocity to the sphere mobilities. In this relationship, a viscous contribution exists when the timereversal symmetry is broken, whereas an elastic contribution is present when the structural symmetry of the microswimmer is broken. As an example of a structured fluid, we consider a polymer gel, which is described by a ``twofluid" model. We demonstrate in detail that the competition between the swimmer size and the polymer mesh size gives rise to the rich dynamics of a threesphere microswimmer. [1] K. Yasuda, R. Okamoto, and S. Komura, EPL 123, 34002 (2018). 
Thu, Nov 8,'18 
Theory Seminar: Fabian Maucher (Durham), tbaPS1.28 
Thu, Nov 15,'18 
Theory Seminar: Robert Jack (Cambridge), tbaPS1.28 
Thu, Nov 22,'18 
Theory Seminar: Patricia Bassereau (Institut Curie)PS1.28 
Thu, Nov 29,'18

Theory Seminar: Thorsten Wahl (Oxford), Tensor network approaches to manybody localisationPS1.28We propose a tensor network encoding the set of all eigenstates of a fully manybody localized system in one dimension. Our construction, conceptually based on the ansatz introduced in Phys. Rev. B 94, 041116(R) (2016), is built from two layers of unitary matrices which act on blocks of ℓcontiguous sites. We argue that this yields an exponential reduction in computational time and memory requirement as compared to all previous approaches for finding a representation of the complete eigenspectrum of large manybody localized systems with a given accuracy. Concretely, we optimize the unitaries by minimizing the magnitude of the commutator of the approximate integrals of motion and the Hamiltonian, which can be done in a local fashion. This further reduces the computational complexity of the tensor networks arising in the minimization process compared to previous work. We test the accuracy of our method by comparing the approximate energy spectrum to exact diagonalization results for the randomfield Heisenberg model on 16 sites. We find that the technique is highly accurate deep in the localized regime and maintains a surprising degree of accuracy in predicting certain local quantities even in the vicinity of the predicted dynamical phase transition. To demonstrate the power of our technique, we study a system of 72 sites, and we are able to see clear signatures of the phase transition. Our work opens a new avenue to study properties of the manybody localization transition in large systems. 
Thu, Dec 6,'18

Theory Seminar: Gabriele Sosso (Warwick, Chemistry)PS1.28tba 
Thu, Dec 13,'18

Theory Seminar: Manuel dos Santos Dias (Forschungszentrum Jülich), Spin interactions, excitations and fluctuations in magnetic adatoms and small clusters from first principlesPS1.28Single atoms are the smallest possible magnets, of interest for fundamental physics and of great promise for technological applications. When assembled on a surface, their properties can be probed and manipulated via scanning tunneling microscopy (STM) and inelastic scanning tunneling spectroscopy (ISTS). However, the theoretical description is challenging, due to the interplay between the reduced dimensionality, the interactions driving the magnetism, and the coupling to the surface. Furthermore, an accurate description of the lowenergy physics due to the spinorbit interaction and external magnetic fields is essential. In Jülich, we have recently developed a hierarchical theoretical approach to the static and dynamics properties of surfacesupported magnetic nanostructures. The materialsspecific information is supplied by density functional theory (DFT), which gives access to groundstate magnetic properties and magnetic interactions. The dynamics of the magnetic moments follows from timedependent DFT (TDDFT), accounting for the impact of the surface electrons on the spin dynamics. The final level of theory addresses manybody effects, either through manybody perturbation theory (MBPT) or by solving a multiorbital Anderson impurity model with quantum Monte Carlo, yielding realistic inelastic transport spectra. In this talk I will present an overview of these theoretical methods while focusing on concrete physical systems: magnetic adatoms and small clusters on metallic surfaces, such as Cu(111) or Pt(111), in close connection with the available experimental information. Different magnetic adatoms on the same surface have very different static and dynamic properties [13], which influence their magnetic stability via zeropoint spin fluctuations [46], while their tunneling spectra are only adequately described in MBPT [79]. The interactions between magnetic adatoms depend not only on their separation but also on their arrangement with respect to the surface, leading to widely different properties of apparently similar clusters [1012]. I conclude by discussing the possible shortcomings and future research directions. References: [1] Phys Rev Lett 111, 157204 (2013); [2] Phys Rev B 91, 075405 (2015); [3] Nat Commun 7, 10454 (2016); [4] Nano Lett 16, 4305 (2016); [5] Phys Rev Lett 119, 017203 (2017); [6] Phys Rev B 96, 144410 (2017); [7] Phys Rev B 89, 235439 (2014); [8] Phys Rev B 93, 115123 (2016); [9] Phys Rev B 93, 035451 (2016); [10] Nat Commun 7, 10620 (2016); [11] Phys Rev B 96, 144401 (2017); [12] Nat Commun 8, 642 (2017) 
Thu, Jan 10,'19

Rebecca Milot (Warwick), Optoelectronic Properties of Hybrid Metal Halide PerovskitesPS1.28 Hybrid metal halide perovskites have shown extraordinary success as active layers in solar cells, with power conversion efficiencies rivalling existing silicon technologies. A benefit of perovskites is that they are comprised of lowcost, earth abundant materials, and perovskite thin films are easily synthesized with simple starting materials. Additionally, they exhibit exceptional optoelectronic properties, which include strong absorption across the entire visible spectrum, long chargecarrier lifetimes, and high chargecarrier mobilities. Opticalpump/THzprobe (OPTP) spectroscopy has proven to be an essential technique for studying the chargecarrier dynamics and chargecarrier mobility in many of these materials including leadbased, tinbased, twodimensional, and mixedhalide/mixedcation perovskites. These studies have determined that the chargecarrier mobility and chargecarrier recombination dynamics are strongly dependent on the chemical composition, defect density, band structure, and crystallinity. 
Thu, Jan 24,'19

Andreas Honecker (Paris Cergy), Thermodynamic properties of the twodimensional ShastrySutherland model for SrCu2(BO3)2PS1.28 
Thu, Jan 31,'19

Piero Naldesi (GrenobleAlpes), The quantum advantage of attractive bosons in a ringshaped potentialPS1.28 
Thu, Feb 7,'19 
Markus Muller (Swansea), tbaPS1.28 
Thu, Feb 14,'19

Anton Souslov (Bath), Chiral Active MetamaterialsPS1.28Active liquids are composed of selfdriven microbots that endow the liquid with a unique set of mechanical characteristics. I will present two designs for materials exhibiting topological states: one using periodic confinement of an active liquid and another using a bulk fluid without periodic order. In a periodic lattice, geometry of confinement controls the structure of topological waves. Without periodic order, topological edge waves can arise in a rotating fluid as a result of the Coriolis force that breaks Galilean invariance and opens a gap at low frequency. I will explore how the number and spatial profile of topological edge states depends on an anomalous response coefficient called odd (or Hall) viscosity. As the sign of odd viscosity changes, a topological phase transition occurs without closing the bulk band gap. For large odd viscosity, this transverse response can be measured via the profile shape of topologically robust edge waves. 
Thu, Feb 21,'19

Frank Kruger (UCL), Suppression of topological Mott insulators and novel quantum criticality of interacting Dirac fermions on the honeycomb latticePS1.28We consider the extended halffilled Hubbard model on the honeycomb lattice for second nearest neighbours interactions. Using a functional integral approach, we find that collective fluctuations suppress topological states and instead favour charge ordering, in agreement with previous numerical studies. However, we show that the critical point is not of the putative Dirac semimetal/Mott insulator variety. Due to the frustrated nature of the interactions, the chargeordered ground state remains metallic with semiDirac excitations. We conjecture that this novel transition is not in the GrossNeveu universality class. 
Thu, Feb 28,'19 1pm  2:00pm 
Chiu Fan Lee (Imperial), Universality in active fluidsPS1.28Active matter is an extreme kind of nonequilibrium system in that detailed balance is broken at the microscopic scale. A typical active system can be a collection of particles that continuously exert mechanical forces on their surrounding environment, and systems of interacting active particles exhibit diverse emergent behaviours. But how do we tell whether the behaviours observed are novel to physics? One way to do so is to determine whether the emergent phenomena are described by novel universal classes. This is the approach I will take in this talk. Specifically, I will start by deriving the hydrodynamic equations of motion for active fluids from symmetry consideration, and then discuss the associated universal behaviours at criticality and in the ordered phase. I will show that some of these universal behaviours can be mapped onto existing equilibrium models, while others are novel or potentially novel to nonequilibrium physics. 
Thu, Mar 14,'19 1pm  2:00pm 
Fabian Essler (Oxford), Full counting statistics in interacting manyparticle systemsPS1.28Motivated by coldatom experiments I consider the problem of determining the probability distributions of subsystem observables one dimensional quantum spin chains and field theories. I focus on the nonequilibrium dynamics of these quantities and show that they give useful insights into the melting of long and shortrange order. 