We investigate the effect of disorder on exciton valley polarization and valley coherence in monolayer WSe2. By analyzing the polarization properties of photoluminescence, the valley coherence (VC) and valley polarization (VP) are quantified across the inhomogeneously broadened exciton resonance. We find that disorder plays a critical role in the exciton VC, while affecting VP less. For different monolayer samples with disorder characterized by their Stokes shift (SS), VC decreases in samples with higher SS while VP does not follow a simple trend. These two methods consistently demonstrate that VC as defined by the degree of linearly polarized photoluminescence is more sensitive to disorder, motivating further theoretical studies.
Bibliographical noteKAUST Repository Item: Exported on 2020-10-01
Acknowledgements: We gratefully acknowledge helpful discussions with Galan Moody and Fengcheng Wu. The spectroscopic experiments were jointly supported by NSF DMR-1306878 (A.S.) and NSF EFMA-1542747 (K.T., K.H., J.S., and X.L.). H.L. also gratefully acknowledges support from Welch Foundation Grant No. F-1662. K.W. and T.T. acknowledge support from the Elemental Strategy Initiative conducted by the MEXT, Japan and JSPS KAKENHI Grant No. JP15K21722.