Superposition of intra- and inter-layer excitons in twistronic MoSe$_2$/WSe$_2$ bilayers probed by resonant Raman scattering

TL;DR

This study uses resonance Raman scattering to directly observe and quantify hybrid exciton states in twistronic MoSe₂/WSe₂ bilayers, revealing how interlayer and intralayer excitons form superposition states due to strong hybridization.

Contribution

It provides the first direct evidence of exciton hybridization in twistronic heterostructures using resonance Raman scattering, enabling quantification of layer composition and hybridization parameters.

Findings

Resonance Raman scattering reveals hybrid exciton states.

Hybridization occurs between specific valence bands in MoSe₂ and WSe₂.

The method allows quantification of layer composition and hybridization strength.

Abstract

Hybridisation of electronic bands of two-dimensional materials, assembled into twistronic heterostructures, enables one to tune their optoelectronic properties by selecting conditions for resonant interlayer hybridisation. Resonant interlayer hybridisation qualitatively modifies the excitons in such heterostructures, transforming these optically active modes into superposition states of interlayer and intralayer excitons. For MoSe$_2$/WSe$_2$ heterostructures, strong hybridization occurs between the holes in the spin-split valence band of WSe$_2$ and in the top valence band of MoSe$_2$, especially when both are bound to the same electron in the lowest conduction band of WSe$_2$. Here we use resonance Raman scattering to provide direct evidence for the hybridisation of excitons in twistronic MoSe$_2$/WSe$_2$ structures, by observing scattering of specific excitons by phonons in both WSe$_2$ and MoSe$_2$. We also demonstrate that resonance Raman scattering spectroscopy opens up a wide range of possibilities for quantifying the layer composition of the superposition states of the exciton and the interlayer hybridisation parameters in heterostructures of two-dimensional materials.