Femtosecond valley polarization and topological resonances in transition metal dichalcogenides

. Azar Oliaei Motlagh, Jhih-Sheng Wu, Vadym Apalkov, Mark I. Stockman

Published 2017-11-28Version 1

We predict a possibility to induce a significant valley polarization in a transition metal dichalcogenide (TMDC) (i.e., $\mathrm{MoS_2}$ and $\mathrm{WS_2}$) monolayer by a fundamentally-shortest circularly-polarized optical pulse consisting of just a single oscillation with duration of a few femtoseconds and a moderate amplitude of $0.2-0.5~\mathrm V/\mathrm{\AA}$. The resulting distribution of electrons in reciprocal space is highly structured and defined by a combination of the atomic-orbital angular momentum conservation and topological resonances that we introduce. These valley degrees of freedom in TMDCs can be used for information processing in PHz-band optoelectronics.