Berlin 2018 – scientific programme

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SYDM: Symposium 2D Materials

SYDM 1: 2D Materials

SYDM 1.2: Invited Talk

Thursday, March 15, 2018, 15:30–16:00, H 0105

Ultrafast valley and spin dynamics in single-layer transition metal dichalcogenides — •Alejandro Molina-Sanchez — Institute of Materials Science (ICMUV), University of Valencia, Spain

Single-layer transition metal dichalcogenides such as MoS₂, MoSe₂, WS₂ and WSe₂ are highly attractive 2D materials due to their interesting optical properties. Recent experiments have shown that a circularly polarised laser field can excite electronic transitions in one of the inequivalent K and K’ valleys. Such selective valley population corresponds to a pseudospin polarization and can serve as a degree of freedom in a valleytronic device provided that the timescale for its depolarization is sufficiently large. The understanding of the photo-generation and the relaxation mechanisms is thus crucial for the use of these materials in future applications. We have developed an atomistic ab-initio methodology to simulate the valley and spin dynamics in semiconducting 2D materials. We are able to calculate the photogeneration and the subsequent relaxation of the valley polarization by several scattering mechanisms. We determine the influence of the electron-phonon interaction on the carrier and spin dynamics, the consequences of the exciton binding energy on the dynamics and the differences in the valley and spin dynamics between distinct 2D materials. Finally, we compare with ultrafast spectroscopy techniques such as time-dependent Kerr rotation and circularly polarized pump-probe experiments.