Excitonic and valleytronic signatures of correlated states at fractional fillings of a moir\'e superlattice

TL;DR

This study reveals how correlated electronic states at fractional fillings in a moiré superlattice influence excitonic and valleytronic properties, showing spectral modulations and valley polarization changes.

Contribution

It provides the first observation of excitonic and valleytronic signatures associated with correlated states at fractional fillings in a moiré superlattice.

Findings

Reflection spectral modulation at fractional fillings

Luminescence spectral modulation of interlayer trions

Suppression of valley polarization at certain fractional fillings

Abstract

Moir\'e superlattices are excellent platforms to realize strongly correlated quantum phenomena, such as Mott insulation and superconductivity. In particular, recent research has revealed stripe phases and generalized Wigner crystals at fractional fillings of moir\'e superlattices. But these experiments have not focused on the influence of electronic crystallization on the excitonic and valleytronic properties of the superlattices. Here we report excitonic and valleytronic signatures of correlated states at fractional fillings in a WSe$_2$/WS$_2$ moir\'e superlattice. We observe reflection spectral modulation of three intralayer moir\'e excitons at filling factors $\nu$ = 1/3 and 2/3. We also observe luminescence spectral modulation of interlayer trions at around a dozen fractional filling factors, including $\nu$ = -3/2, 1/4, 1/3, 2/5, 2/3, 6/7, 5/3. In addition, the valley polarization of interlayer trions is noticeably suppressed at some fractional fillings. These results demonstrate a new regime of light-matter interactions, in which electron crystallization significantly modulates the absorption, emission, and valley dynamics of the excitonic states in a moir\'e superlattice.