Confined-state physics and signs of fermionization of moir\'e excitons in WSe$_2$/MoSe$_2$ heterobilayers

TL;DR

This paper investigates moiré excitons in WSe2/MoSe2 heterobilayers, revealing signs of fermionization and unconventional spectral shifts, suggesting a fermionic behavior in these excitonic states.

Contribution

It introduces a fermionic model to explain the spectral shifts of moiré excitons, extending the bosonic interpretation and highlighting fermionization effects in these systems.

Findings

Observation of saturating blueshifts in exciton resonances

Spectral shifts explained by fermionic saturable absorber model

Analogy between moiré excitons and quantum-dot models

Abstract

We revisit and extend the standard bosonic interpretation of interlayer excitons in the moir\'e potential of twisted heterostructures of transition-metal dichalcogenides. In our experiments, we probe a high quality MoSe$_2$/WSe$_2$ van der Waals bilayer heterostructure via density-dependent photoluminescence spectroscopy and reveal strongly developed, unconventional spectral shifts of the emergent moir\'e exciton resonances. The observation of saturating blueshifts of successive exciton resonances allow us to explain their physics in terms of a model utilizing fermionic saturable absorbers. This approach is strongly inspired by established quantum-dot models, which underlines the close analogy of interlayer excitons trapped in pockets of the moir\'e potential, and quantum emitters with discrete eigenstates.