Monolayers of semiconducting transition metal dichalcogenides are two-dimensional direct-gap systems which host tightly-bound excitons with an internal degree of freedom corresponding to the valley of the constituting carriers. Strong spin-orbit interaction and the resulting ordering of the spin-split subbands in the valence and conduction bands makes the lowest-lying excitons in WX2 (X~being S or Se) spin-forbidden and optically dark. With polarization-resolved photoluminescence experiments performed on a WSe2 monolayer encapsulated in a hexagonal boron nitride, we show how the intrinsic exchange interaction in combination with the applied in-plane and/or out-of-plane magnetic fields enables one to probe and manipulate the valley degree of freedom of the dark excitons.
@article{arxiv.1901.04431,
title = {Probing and manipulating valley coherence of dark excitons in monolayer WSe$_2$},
author = {M. R. Molas and A. O. Slobodeniuk and T. Kazimierczuk and K. Nogajewski and M. Bartos and P. Kapuściński and K. Oreszczuk and K. Watanabe and T. Taniguchi and C. Faugeras and P. Kossacki and D. M. Basko and M. Potemski},
journal= {arXiv preprint arXiv:1901.04431},
year = {2019}
}