Phonon-induced exciton weak localization in two-dimensional semiconductors

TL;DR

This paper theoretically investigates how quantum interference effects, specifically weak localization caused by phonon interactions, influence exciton diffusion in atomically thin two-dimensional semiconductors, highlighting regimes of pronounced effects.

Contribution

It introduces a theoretical framework for understanding phonon-induced weak localization of excitons in 2D materials, considering various phonon types and higher-order effects.

Findings

Weak localization affects exciton diffusion even with long-wavelength phonons.

Regimes where weak localization is particularly strong are identified.

Role of free charge carriers and higher-order effects are briefly analyzed.

Abstract

We study theoretically the contribution of quantum effects to the exciton diffusion coefficient in atomically thin crystals. It is related to the weak localization caused by the interference of excitonic wavefunctions on the trajectories with closed loops. Due to a weak inelasticity of the exciton-phonon interaction the effect is present even if the excitons are scattered by long-wavelength acoustic phonons. We consider exciton interaction with longitudinal acoustic phonons with linear dispersion and with flexural phonons with quadratic dispersion. We identify the regimes where the weak localization effect can be particularly pronounced. We also briefly address the role of free charge carriers in the exciton quantum transport and, within the self-consistent theory of localization, the weak localization effects beyond the lowest order.