Electrically tunable valley polarization and valley coherence in monolayer WSe 2 embedded in a van der Waals heterostructure

Abstract

The valley degree of freedom possessed by electronic excitations in transition metal dichalcogenides is providing new opportunities for information processing and optoelectronics. Valley contrasting polarization selection rules present unique opportunities for optical control in valleytronic devices. Critical to devices leveraging the valley degree of freedom is the ability to tailor optical valley polarizability and its degree of coherence. In this manuscript, we demonstrate the electric field control of both valley polarization and valley coherence in a monolayer of tungsten diselenide that has been incorporated into a van der Waals heterostructure. We find the competition between electron-hole exchange, radiative decay and pure dephasing determines the ability to control valley polarization and coherence of both excitons and trions.