Long Range Coherent Valley Pseudospin Transport via Bloch Surface Wave Polaritons in Monolayer Transition Metal Dichalcogenides

Abstract The feasibility of low-dimensional transition metal dichalcogenides (TMDs) as a platform for valleytronics relies on the ability to control the dynamics of the valley pseudospins. Here, we present long-range coherent valley pseudospin transport assisted by Bloch surface wave exciton-polaritons (BSWPs). We resolve the BSWP transport in exfoliated WS2 over distances exceeding 10 μm in both spatial and polarization spaces via momentum-selected circular dichroism spectroscopy at cryogenic temperatures. We show that the trajectories on the Poincaré sphere reflect hybrid light–matter polarization dynamics. Furthermore, we show that the BSWP transport can be optically or magnetically controlled through the photonic or the excitonic component. Our work demonstrates the ability to coherently transport valley pseudospin information over long distances and establishes the feasibility of an all-axis controllable quantum system in the spatial, spectral, momentum, and polarization domains.