Extended spatial coherence of interlayer excitons in MoSe$_2$/WSe$_2$ heterobilayers

TL;DR

This study demonstrates that interlayer excitons in MoSe₂/WSe₂ heterobilayers exhibit extended spatial coherence at low temperatures, indicating a possible coherent many-body state, with coherence diminishing as temperature increases.

Contribution

It provides the first detailed measurement of spatial coherence length and temporal coherence of interlayer excitons in heterobilayers using interferometry.

Findings

Spatial coherence length reaches the size of exciton ensembles below 10 K.

High temporal coherence observed at low temperatures.

Coherence diminishes with increasing temperature due to thermal effects.

Abstract

We report on the spatial coherence of interlayer exciton ensembles as formed in MoSe$_2$/WSe$_2$ heterostructures and characterized by point-inversion Michelson-Morley interferometry. Below 10 K, the measured spatial coherence length of the interlayer excitons reaches values equivalent to the lateral expansion of the exciton ensembles. In this regime, the light emission of the excitons turns out to be homogeneously broadened in energy with a high temporal coherence. At higher temperatures, both the spatial coherence length and the temporal coherence time decrease, most likely because of thermal processes. The presented findings point towards a spatially extended, coherent many-body state of interlayer excitons at low temperature.