Anomalous Rotation Of The Linearly Polarized Emission Of Bright Excitons In Strained Wse2 Monolayers Under High Magnetic Fields

Linearly polarized microphotoluminescence (mu-PL) measurements of strained WSe2 monolayers in out-of-plane high magnetic fields are presented. At low temperature, a splitting of the bright exciton emission into two exciton components is observed, which is attributed to an in-plane uniaxial strain based on the full polarization dependence of the photoluminescence spectrum. High magnetic field measurements directly reveal a distinct evolution of the linear polarization and allows us to extract the valley coherence time constants (T-s2(*)) for both exciton components. For the high-energy transition of the exciton, the valley coherence time similar or equal to 0.45 ps, closely matching T-s2(*) of an unstrained monolayer (similar or equal to 0.34 ps). For the low-energy exciton, however, T-s2(*) is four times larger, similar or equal to 1.97 ps. This valley coherence time observed here may be explored for future valleytronic applications.