Exciton (De)Localization and Dissociation in Heterogeneous Semiconductors from First Principles Computational Modeling
Marina R. Filip, Department of Physics, University of Oxford

Understanding the physics of how excitons form, delocalize and dissociate is of key importance to the functionality of a wide range of applications, such as photovoltaics, lighting and lasing. Development of new computational modeling techniques based on density functional theory (DFT) and many body perturbation theory capable to describe interactions between excitons and other quasiparticles constitutes a frontier first principles computational modeling of materials. The GW+Bethe-Salpeter Equation (BSE) approach [1,2] is the state-of-the-art approach to compute optical excitation energies in semiconductors and insulators and provides the foundation of new methods aimed at describing complex excited state phenomena.

In the first part of my talk, I will present a new methodological development that generalizes the BSE to include the impact of ionic vibrations on the dielectric screening of excitons [3,4], and show how this allows us to compute temperature dependent exciton binding energies, as well the rate of dissociation of excitons upon scattering with phonons. In the second part of my talk (as time allows), I will present our recent study of layered halide perovskites and hetero-structures [5-8], in which excitons display very interesting delocalization, and discuss the mechanism for tuning the excited-state properties of these heterogeneous semiconductors.Bio: Marina Filip is an Associate Professor of Condensed Matter Physics at the University of Oxford and a Tutorial Fellow in Physics at University College, Oxford. Before joining the Oxford Physics faculty in February 2020, Marina was a postdoctoral scholar in the Physics Department at UC Berkeley and Lawrence Berkeley National Laboratory (2018-2020) and the Materials Department at the University of Oxford (2015-2018). Marina received her doctorate in Materials Science from the University of Oxford in 2016 (having defended 2015). Before this, Marina completed her undergraduate studies in Physics, at the University of Bucharest, Romania. Marina was recently awarded the 2024 IUPAP Early Career Scientist Prize in Semiconductor Physics, and a Somorjai Miller Visiting Professorship at UC Berkeley for Fall 2024. She was previously selected as part of the 2019 class of “Rising Stars in Physics”, and between 2015 and 2018 she was awarded a Junior Research Fellowship from Wolfson College Oxford.