Anisotropic exciton transport in transition-metal dichalcogenides

TL;DR

This paper proposes an experimental method to observe anisotropic exciton transport in monolayer transition-metal dichalcogenides, highlighting the effects of linear dispersion components and polarization on exciton dynamics.

Contribution

It introduces a novel experimental approach to detect linear dispersion signatures and anisotropic transport in excitons and exciton-polaritons in 2D materials.

Findings

Linearly polarized light induces anisotropic exciton transport.

Effects persist under moderate disorder conditions.

Similar phenomena observed in exciton-polaritons with less stringent requirements.

Abstract

Due to the Coulomb interaction exciton eignestates in monolayer transitional metal dichalcogenides are coherent superposition of two valleys. The exciton band which couples to the transverse electric mode of light has parabolic dispersion for the center of mass momentum, whereas the one which couples to the transverse magnetic mode has both parabolic and linear components. In this work we present an experimental proposal to observe the signatures of linear component of the dispersion. In particular, it is demonstrated that by pumping the system with linearly polarized light the exciton transport is anisotropic compared to circularly polarized pump. We show that the results persist for moderate level of disorder present in realistic systems. Finally, we demonstrate that similar effects can be obtained for positively detuned exciton-polaritons, in less stringent experimental requirements compared to bare exciton case.