Background

I graduated from the University of Warwick in summer 2019 with a BSc MPhys in Physics. My final year project involved using scanning and transmission electron microscopy techniques to analyse the structural and optical properties of nanowire heterostructures, completed under the supervision of Prof. Ana Sanchez of the Microscopy group. Currently I am completing my PhD joint with the Microscopy group at the University of Warwick, with supervision by Prof. Neil Wilson, and the I05 beamline at Diamond Light Source, with supervision by Dr Cephise Cacho.

Research Interests

My research is focused around 2D materials and van der Waals heterostructures, specifically using angle-resolved photoemission spectroscopy (ARPES) to investigate their layer-dependent band structure and interlayer effects. This requires the use of a spatially-resolved ARPES beam, available only at select synchrotron beamlines (e.g. I05 at Diamond Light Source/Spectromicoscopy at Elettra). An extension of this work is to use in situ electrostatic gating to visualize the conduction band of 2D semiconductors, as well as observe band structure renormalisation and other gate dependent effects.

Recent Work

Recently I have been investigating the band structure of twisted multilayer graphene. Stacking layers of graphene with a relative twist angle produces a Moiré potential that modulates the underlying band structure of the individual layers. At specific twist angles (known as the magic angles) a flat band emerges at the Fermi level, which can give rise to correlated states, e.g. Mott-like insulator states and superconductivity. Below are recent results from a twisted double-bilayer graphene structure. The band structure can be seen to evolve with decreasing twist angle, eventually resulting in a flat band. These samples come from a collaboration with the National Graphene Institute at the University of Manchester.

Publications

• "Zn₂GeO₄/SnO₂ Nanowire Heterostructures Driven by Plateau-Rayleigh Instability", J. Dolado, K. L. Renforth, J. E. Nunn, S. A. Hindsmarsh, P. Hidalgo, A. M. Sánchez, B. Méndez, Crystal Growth & Design 20, 506-513 (2020)

Conferences

• SPIE Photonex + Vaccum Technologies 2021, Photoemssion Spectroscopy for Materials Analysis, Glasgow (talk) - "Twist-dependent band structure of multilayer graphene revealed by microARPES"

James Nunn