Moir\'e Excitons Correlated with Superlattice Structure in Twisted WSe$_2$/WSe$_2$ Homobilayers

TL;DR

This study uses advanced microscopy to directly link moiré superlattice structures in twisted WSe₂ bilayers with distinct exciton species, revealing their tunability and valley coherence, advancing quantum optoelectronics.

Contribution

It provides the first direct correlation between local moiré structure and optical exciton properties in twisted TMD bilayers using scanning electron microscopy.

Findings

Two distinct exciton species emerge with increasing moiré periodicity.

Excitons can be individually tuned via electrostatic gating.

Different valley coherence properties are observed for the exciton species.

Abstract

Moir\'e superlattices in twisted van der Waals materials constitute a promising platform for engineering electronic and optical properties. However, a major obstacle to fully understanding these systems and harnessing their potential is the limited ability to correlate the local moir\'e structure with optical properties. By using a recently developed scanning electron microscopy technique to image twisted WSe$_2$/WSe$_2$ bilayers, we directly correlate increasing moir\'e periodicity with the emergence of two distinct exciton species. These can be tuned individually through electrostatic gating, and feature different valley coherence properties. Our observations can be understood as resulting from an array of two intralayer exciton species residing in alternating locations in the superlattice, and illuminate the influence of the moir\'e potential on lateral exciton motion. They open up new avenues for controlling exciton arrays in twisted TMDs, with applications in quantum optoelectronics and explorations of novel many body systems.