Momentum-Resolved Exciton Coupling and Valley Polarization Dynamics in Monolayer WS2

Using time- and angle-resolved photoemission, we present momentum- and energy-resolved measurements of exciton coupling in monolayer WS2. We observe strong intravalley coupling between the B-1s exciton and A(n>1) states. Our measurements indicate that the dominant valley depolarization mechanism conserves the exciton binding energy and momentum. While this conservation is consistent with Coulomb exchange-driven valley depolarization, we do not observe a momentum or energy dependence to the depolarization rate as would be expected for the exchange-based mechanism.

Automated summary

Using time- and angle-resolved photoemission, the study investigates exciton coupling in monolayer WS2 and finds strong intravalley coupling between the B-1s exciton and A(n>1) states. The measurements indicate that the dominant valley depolarization mechanism conserves the exciton binding energy and momentum, but do not show momentum or energy dependence as expected for the exchange-based mechanism.