Hybrid moiré excitons in a strained heterobilayer of transition metal dichalcogenides

Abstract

In this paper, we theoretically investigate the effects of twist and heterostrain on moiré excitons in the MoSe₂/WSe₂ heterobilayer. Using a continuum model, we analyze the band structures and wavefunction distributions of moiré excitons, photoluminescence spectra, and the hybridization between interlayer and intralayer moiré excitons. Our key findings reveal that the three-fold rotational symmetry breaking induced by heterostrain leads to significant tunability of the exciton band structure, thereby modifying the distribution of bright-state energies around the light cone. Moreover, tuning the strain magnitude and direction can enhance the brightness of moiré excitons, highlighting the crucial role of strain orientation in excitonic optical modulator applications. Furthermore, the interplay between twist and strain induces a high degree of tunability in the mixing of interlayer and intralayer exciton wavefunctions. Remarkably, under specific strain magnitudes and directions—such as normal compressive strain—we observe the emergence of a topological moiré exciton Chern insulator, characterized by protected edge modes. Our results may pave the way for exploring novel topological exciton phenomena and moiré exciton-correlated physics. They are particularly intriguing for potential device applications with the excitonic quantum anomalous Hall effect (EQAHE) enabled by the combined effects of strain and twist.