Valley-exchange coupling probed by angle-resolved photoluminescence

TL;DR

This paper predicts that angle-resolved photoluminescence, influenced by valley-exchange coupling and magnetic fields, can effectively probe excitonic dispersion changes in monolayer transition metal dichalcogenides.

Contribution

It introduces a novel method using angle-resolved photoluminescence with polarization and magnetic fields to investigate valley-exchange coupling effects.

Findings

Angle dependence of emission intensity reveals exchange effects.

Magnetic fields tune emission characteristics via Zeeman shifts.

Proposed measurements can verify valley-exchange coupling influence.

Abstract

The optical properties of monolayer transition metal dichalcogenides are dominated by tightly-bound excitons. They form at distinct valleys in reciprocal space, and can interact via the valley-exchange coupling, modifying their dispersion considerably. Here, we predict that angle-resolved photoluminescence can be used to probe the changes of the excitonic dispersion. The exchange-coupling leads to a unique angle dependence of the emission intensity for both circularly and linearly-polarised 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 dispersionand its signatures in optical spectra