Abstract

In this talk I will discuss new developments and applications by our group for what pertains the inclusion of electron-phonon, electron-electron and phonon-phonon interactions in beyond state of the art computational schemes for the calculation of spectroscopic quantities. I will mainly focus on two aspects.

(i) Optical properties of materials: I will present a new computational scheme to calculate the optical properties of materials from first principles. This approach combines the recently introduced cumulant expansion for the two-particle correlation function [1] with a proper treatment of the exciton-phonon coupling [2]. I will present an application to single-layer boron nitride and discuss its absorption and photoluminescence spectra, providing a novel interpretation for its controversial photoluminescence spectral features [3,4].

(ii) Non-equilibrium (ultrafast) spectroscopy: I will introduce a new workflow, developed within the EPIq code [5], for the description the real-time carrier dynamics in pump-probe experiments on semiconductors. The implementation is based on an equal footing treatment of electron-electron, electron-phonon and phonon-phonon scattering channels. Within this approach we are able to describe the real-time evolution of photoexcited electron-hole plasma and to access many experimentally measurable time-resolved observables related to the coherent phonon dynamics and its damping by the inclusion of anharmonic effects.

This work was funded by the European Union (ERC, DELIGHT , 101052708). Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or the European Research Council. Neither the European Union nor the granting authority can be held responsible for them.

[1] P. Cudazzo, L. Reining, Phys. Rev. Research, 2, 012032 (2020)

[2] P. Cudazzo, Phys. Rev. B, 108, 165101 (2023)

[3] C. Elias, P. Valvin, T. Pelini, A. Summerfield, C. Mellor, T. Cheng, L. Eaves, C. Foxon, P. Beton, S. Novikov, B. Gil, G. Cassabois, Nat. Commun., 10, 2639 (2019)

[4] A. Rousseau, L. Ren, A. Durand, P. Valvin, B. Gil, K. Watanabe, T. Taniguchi, B. Urbaszek, X. Marie, C. Robert, G. Cassabois, Nano Lett., 21, 10133-10138 (2021)

[5] G. Marini, G. Marchese, G. Profeta, J. Sjakste, F. Macheda, N. Vast, F. Mauri, M. Calandra, Computer Physics Communications, 295, 108950 (2024)