Berlin 2024 – wissenschaftliches Programm

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SYES: Symposium Advances in Ab-Initio Electronic Structure Theory of Time-Dependent and Non-Equilibrium Phenomena

SYES 1: Advances in Ab-Initio Electronic Structure Theory of Time-Dependent and Non-Equilibrium Phenomena

SYES 1.4: Hauptvortrag

Dienstag, 19. März 2024, 11:15–11:45, H 0105

Phonon screening of excitons in semiconductors and insulators from first principles — •Marina Rucsandra Filip — University of Oxford, Department of Physics

Excitons are correlated electron hole pairs, which form in semiconductors and insulators upon absorption of light. Understanding the formation, dynamics and dissociation of excitons is of key importance for optoelectronic applications, such as photovoltaic and light emitting devices. First principles methods based on the GW + Bethe Salpeter equation (BSE) [1] have been playing a key role in developing this understanding from an atomistic perspective. In this talk, I will discuss a framework that we have recently developed [2,3], to understand the role played by ionic vibrations on the properties of excitons. I will motivate this development by highlighting the importance of phonons for the dielectric screening of excitons using a model Wannier-Mott (hydrogenic) picture, and parameters corresponding to well known semiconductors (III-V, halide perovskites). I will then show how this model picture can be generalized into a first principles approach, based on the standard GW+BSE framework. I will show how our implementation allows us to perform fully converged calculations of phonon screening effects, and identify the carrier-phonon interactions which dominate phonon screening in different materials. [1] Rohlfing & Louie, Phys. Rev. Lett. 81, 2312 (1998). [2] Filip, Haber & Neaton, Phys. Rev. Lett., 127, 067401 (2021). [3] Alvertis, Haber, Li, Coveney, Louie, Filip & Neaton, Submitted (2023). Work supported by the EPSRC, with computational resources from TACC at UT Austin.

Keywords: excitons; phonons; Bethe-Salpeter Equation; First Principles; semiconductors