Anomalous valley Hall dynamics of exciton-polaritons

TL;DR

This paper demonstrates an anomalous valley Hall effect in monolayer WS2 exciton-polaritons, revealing ultrafast valley transport driven by strain-induced pseudomagnetic fields, with implications for valleytronics and topological photonics.

Contribution

It reports the first observation of an anomalous valley Hall effect in exciton-polaritons, highlighting strain-induced pseudomagnetic fields as the underlying mechanism.

Findings

Visualization of symmetry-breaking spatial separation of polaritons from opposite valleys.

Ultrafast Hall drift velocity of approximately 10^5 m/s.

Identification of strain-induced pseudomagnetic fields as the cause.

Abstract

The valley degree of freedom in atomically thin transition-metal dichalcogenides provides a natural binary index for information processing. Exciton-polaritons formed under strong light-matter coupling offer a promising route to overcome the limited lifetime and transport of bare valley excitons. Here we report an anomalous optical valley Hall effect in a monolayer WS2 exciton-polariton system. Using polarization- and time-resolved real-space imaging, we directly visualize a symmetry-breaking spatial separation of polaritons from opposite valleys under linearly polarized excitation, accompanied by an ultrafast Hall drift velocity on the order of 10^5 m/s. This behaviour cannot be accounted for by conventional cavity-induced mechanisms and instead points to a strain-induced synthetic pseudomagnetic field acting on the excitonic component of polaritons. Our results establish exciton-polaritons as a high-speed and optically accessible platform for valley transport, opening pathways towards tunable valleytronic and topological photonic devices.