Hybrid moiré excitons in strained heterobilayer of transition metal dichalcogenides

Abstract

In this paper, we theoretically study the effects of twist and heterostrain on moiré excitons in the $MoSe_2/WSe_2$ 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, under the influence of twisting effect, moiré excitons flat bands emerge. Additionally, we observe that the bright states exhibit a linear and quadratic dependence on the twist angle. We predict the existence of a critical twist angle, $\theta_c \simeq 2^\circ$, which distinguishes between localized and delocalized regimes. In contrast, the three-fold rotational symmetry breaking induced by heterostrain leads to significant tunability of the exciton band structure and the distribution of bright states. Moreover, exploring the strain magnitude and direction may enhance the brightness of moiré exciton bright states, emphasizing the importance of strain orientation in excitonic optical modulator applications. Furthermore, the combined effects of twist and strain result in a high degree of tunability in the hybridization between interlayer and intralayer excitons. Interestingly, under specific strain magnitudes and directions, such as normal compressive strain, we observe the emergence of a topological moiré exciton Chern insulator, featuring the protected edge modes. Our predictions may pave the way for exploring novel topological exciton phenomena and moiré exciton-correlated physics. They are particularly intriguing for potential device applications in the excitonic quantum anomalous Hall effect (EQAHE) enabled by the combined effects of strain and twist.