Exciton diffusion in monolayer semiconductors with suppressed disorder

Abstract

Monolayer semiconductors with suppressed environmental disorder from encapsulation in high-quality insulators provide a versatile platform to study the propagation of excitonic quasiparticles at ambient conditions. Using time-resolved emission microscopy, the authors monitored linear and nonlinear exciton diffusion in single layers of tungsten disulfide, observing highly mobile excitons with nonmonotonic density dependence of the diffusion. Combining experiment and theory, the authors discuss the impact of multivalley band structure, the role of bound and free charge carriers, the interplay of nonradiative recombination and diffusion as well as the suppressed Auger recombination.