Exciton Hall effect and valley-exciton transport

Spontaneous Hall effect caused by the Berry curvature (the internal magnetic field in momentum space) has recently attracted vast interest for investigating internal quantum degrees of freedom in solids. Here we report a new type of spontaneous Hall effect, exciton Hall effect (EHE), in monolayer MoS₂[1].
The valley-coupled excitons in transition metal dichalcogenides are expected to possess valley-contrasting Berry curvature, which gives rise the Hall effect of valley excitons without magnetic fields. We observed the EHE and valley-contrasting exciton transport in a micrometer scale by using polarization-resolved photoluminescence mapping. The valley diffusion length is deduced to be around 2 μm at 30 K in monolayer MoS₂. The EHE and the consequent valley transport can push ahead exciton-based valleytronics in two-dimensional materials.
[1] M. Onga et al., Nat. Mater. (2017). doi:10.1038/nmat4996.