Long-range quantum transport of indirect excitons in van der Waals heterostructure

TL;DR

This paper demonstrates long-range propagation of interlayer excitons in a MoSe2/WSe2 heterostructure, achieving propagation distances up to 100 micrometers by resonant optical excitation, overcoming previous localization limitations.

Contribution

It reports the first observation of macroscopically long-range interlayer exciton propagation in TMD heterostructures using resonant excitation to suppress localization.

Findings

IX propagation distance up to 100 μm achieved

Resonant excitation enhances IX transport

Suppression of localization and scattering observed

Abstract

Long lifetimes of spatially indirect excitons (IXs), also known as interlayer excitons, make possible long-range IX propagation. Van der Waals heterostructures composed of atomically thin layers of transition-metal dichalcogenides (TMDs) give an opportunity to realize excitons with high binding energies and provide a materials platform for the realization of both excitonic quantum phenomena and excitonic devices. Propagation of IXs in TMD heterostructures is intensively studied. However, in spite of long IX lifetimes, orders of magnitude longer than lifetimes of spatially direct excitons (DXs), a relatively short-range IX propagation with the $1/e$ decay distances $d_{1/e}$ up to few $\mu$m was reported in the studies of TMD heterostructures. The short-range of IX propagation originates from in-plane potentials, which localize excitons and suppress exciton transport. In particular, significant in-plane moir\'e potentials predicted in TMD heterostructures can cause an obstacle for IX propagation. In this work, we realize in a MoSe$_2$/WSe$_2$ heterostructure a macroscopically long-range IX propagation with $d_{1/e}$ reaching $\sim 100$ $\mu$m. The strong enhancement of IX propagation is realized using an optical excitation resonant to DXs in the heterostructure. The strong enhancement of IX propagation originates from the suppression of IX localization and scattering and is observed in the quantum regime.