# Long-range spatial extension of exciton states in van der Waals heterostructure

## TL;DR

This study reveals that spatially indirect excitons in a MoSe2/WSe2 heterostructure exhibit narrow photoluminescence lines that extend over micrometer scales, indicating confinement in a weakly disordered moiré potential.

## Contribution

It demonstrates the macroscopic spatial extension of localized exciton states in a van der Waals heterostructure, revealing their confinement in a moiré potential.

## Key findings

- Narrow PL lines vanish with increasing exciton density.
- Narrow lines extend over several micrometers.
- Excitons are confined in a weakly disordered moiré potential.

## Abstract

Narrow lines in photoluminescence (PL) spectra of excitons are characteristic of low-dimensional semiconductors. These lines correspond to the emission of exciton states in local minima of a potential energy landscape formed by fluctuations of the local exciton environment in the heterostructure. The spatial extension of such states was in the nanometer range. In this work, we present studies of narrow lines in PL spectra of spatially indirect excitons (IXs) in a MoSe$_2$/WSe$_2$ van der Waals heterostructure. The narrow lines vanish with increasing IX density. The disappearance of narrow lines correlates with the onset of IX transport, indicating that the narrow lines correspond to localized exciton states. The narrow lines extend over distances reaching several micrometers and over areas reaching ca. ten percent of the sample area. This macroscopic spatial extension of the exciton states, corresponding to the narrow lines, indicates a deviation of the exciton energy landscape from random potential and shows that the excitons are confined in moir\'e potential with a weak disorder.