Room temperature interlayer exciton valley polarization and valley Hall effect

TL;DR

This paper demonstrates room temperature interlayer exciton valley polarization and valley Hall effect in MoS2/WSe2 heterostructures, revealing potential for opto-valleytronic devices with long-lived valley states.

Contribution

It reports the first observation of interlayer exciton valley polarization and valley Hall effect at room temperature in TMD heterostructures.

Findings

Valley polarization observed via polarization-dependent photoluminescence mapping.

Exciton separation occurs perpendicular to their transport directions.

Valley Hall effect persists at room temperature, unlike in monolayer TMDs.

Abstract

For monolayer transition metal chalcogenides (TMDs), electrons and excitons in different valleys can be driven to opposite directions by the Berry curvature, serving as a valley-dependent effective magnetic field. In addition to monolayer TMDs, Van der Waals heterostructures provide an attractive platform for emerging valley physics and devices with superior physics properties. Interlayer excitons in TMD heterostructures have a long valley lifetime as compared to monolayer intralayer excitons. Here we report an interlayer exciton valley polarization and valley Hall effect in MoS2/WSe2 in room temperature. The separation for excitons with different valley index is observed with polarization-dependent photoluminescence mapping. The exciton separation is perpendicular to their transport directions. The valley Hall effect for indirect excitons is sustained even at room temperature, in contrast with the cryo-temperatures in previous experiments in monolayer TMDs. Room temperature demonstration of the indirect exciton valley polarization and valley Hall effect might open new perspectives for the development of opto-valleytronic devices based on TMD heterostructures.