Skew Scattering and Side Jump Drive Exciton Valley Hall Effect in Two-Dimensional Crystals

TL;DR

This paper reveals that the exciton valley Hall effect in two-dimensional crystals is driven by side-jump and skew scattering mechanisms, not the Berry curvature-induced anomalous velocity, and develops a comprehensive microscopic theory for it.

Contribution

The study introduces a microscopic theory showing the exciton valley Hall effect is governed by scattering mechanisms rather than Berry curvature effects.

Findings

Anomalous velocity does not contribute to the effect.

The effect's sensitivity to drag force origin and scattering processes.

Extended drift-diffusion model for exciton density and valley polarization.

Abstract

Exciton Valley Hall effect is the spatial separation of the valley-tagged excitons in the presence of a drag force. Usually, the effect is associated with the anomalous velocity acquired by the particles due to the Berry curvature of the Bloch bands. Here we show that the anomalous velocity plays no role in the exciton valley Hall effect, which is governed by the side-jump and skew scattering mechanisms. We develop microscopic theory of the exciton valley Hall effect in the presence of synthetic electric field and phonon drag and calculate all relevant contributions to the valley Hall current also demonstrating the cancellation of the anomalous velocity. The sensitivity of the effect to the origin of the drag force and to the scattering processes is shown. We extend the drift-diffusion model to account for the valley Hall effect and calculate the exciton density and valley polarization profiles.