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TT: Fachverband Tiefe Temperaturen

TT 87: Optics and Light-Matter Interaction with Excitons in 2D Materials (joint session HL, DS, O, and TT, organized by DS)

TT 87.4: Vortrag

Freitag, 24. März 2017, 12:00–12:15, CHE 89

Ab-initio calculations of valley depolarization in single-layer WSe₂ mediated by electron-phonon interaction — Alejandro Molina-Sánchez¹, Davide Sangalli², Andrea Marini², and •Ludger Wirtz¹ — ¹Physics and Materials Science Research Unit, University of Luxembourg, Luxembourg — ²Istituto de Strutura della Materia (CNR), CNR, Monterrotondo, Rome, Italy

Circularly polarized light can be used to selectively populate the K⁺ and K⁻ electronic valleys of single-layer WSe₂. Valley depolarization has been measured through time-dependent Kerr experiments (measuring the rotation of a linearly polarized probe pulse applied after a circularly polarized pump pulse) by several groups. However, the depolarization mechanism still remains largely debated. Using an ab-initio implementation of time-dependent many-body perturbation theory (including electron-electron, electron-hole, and electron-phonon interaction), we solve unambiguously the debate about the dominant mechanism that drives the valley depolarization. The decay dynamics and peculiar temperature dependence (observed in recent experiments) is explained in terms of electron-phonon mediated processes that induce spin-flip inter-valley transitions.