Valley-exchange coupling probed by angle-resolved photoluminescence

Abstract

The optical properties of monolayer transition metal dichalcogenides are dominated by tightlybound excitons. They form at distinct valleys in reciprocal space, and can interact via the valleyexchange coupling, modifying their dispersion considerably. Here, we predict that angle-resolved photoluminescence can be used to probe the changes of the excitonic dispersion. The exchangecoupling leads to a unique angle dependence of the emission intensity for both circularly and linearlypolarised light. We show that these emission characteristics can be strongly tuned by an external magnetic field due to the valley-specific Zeeman-shift. We propose that angle-dependent photoluminescence measurements involving both circular and linear optical polarisation as well as magnetic fields should act as strong verification of the role of valley-exchange coupling on excitonic dispersion and its signatures in optical spectra.