Dielectric screening and relaxation dynamics of excited electrons in oxide materials

André Schleife

doi:10.1117/12.2591767

6 March 2021 Dielectric screening and relaxation dynamics of excited electrons in oxide materials

André Schleife

Proceedings Volume 11687, Oxide-based Materials and Devices XII; 1168724 (2021) https://doi.org/10.1117/12.2591767
Event: SPIE OPTO, 2021, Online Only

Abstract

Electronic excitations and their real-time dynamics are critical for how we use optical materials in applications and how we probe carrier thermalization and energy transfer between electrons and ions. Recent experimental advances allow us to do so with unprecedented accuracy and time resolution, however, their interpretation relies on detailed theoretical understanding. This can be provided by first-principles theoretical-spectroscopy, based on many-body perturbation theory and time-dependent density functional theory. This talk will briefly discuss how we use quantum-mechanical first-principles simulations, based on the GW+BSE approach, to provide an accurate description of optical properties for oxide materials. I will then show how different dielectric screening contributions affect this description: More specifically, we compare screening due to free carriers for doped systems, electronic interband screening, and lattice polarizability. The first effect can be modeled using a Thomas-Fermi description of free electrons, and the latter can be described using the Froehlich model. Incorporating these into our simulations, allows us to quantify how exciton binding energies are reduced by additional screening and how optical and excitonic properties of various transparent conducting oxides are impacted. Finally, we explore carrier dynamics emerging in ZnO after an initial optical excitation by imposing occupation numbers on electron and hole Kohn-Sham states. The resulting temperature-dependent optical spectra allow us to draw conclusions about contributions from band-gap renormalization, Burstein-Moss shift, and inter-band transitions in excellent agreement with experiment.

Conference Presentation

Citation Download Citation

André Schleife "Dielectric screening and relaxation dynamics of excited electrons in oxide materials", Proc. SPIE 11687, Oxide-based Materials and Devices XII, 1168724 (6 March 2021); https://doi.org/10.1117/12.2591767

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KEYWORDS

Electrons

Dielectrics

Oxides

Systems modeling

Excitons

Ions

Optical properties

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