Continuum model study of optical absorption by hybridized moir\'e excitons in transition metal dichalcogenide heterobilayers

Abstract

We propose a continuum model for the theoretical study of hybridized moir\'e excitons in transition metal dichalcogenides heterobilayers, and we use a variational method to solve the exciton wavefunction and calculate the optical absorption spectrum. The exciton continuum model is built by the charge continuum model for electrons and holes in moir\'e superlattices, thereby preserving the moir\'e periodicity and lattice symmetry from the charge continuum model. The momentum-space shift of interlayer electron-hole distribution is included, and thus the indirect nature of interlayer excitons is described. The spin and valley degrees of freedom and related interactions are omitted, except for the spin-orbit energy splitting of A and B excitons. This continuum model is applied to the simulation of optical absorption by hybridized moir\'e excitons in $\text{WSe}_2$/$\text{WS}_2$ and $\text{MoSe}_2$/$\text{WS}_2$ heterobilayers. Twist-angle and electric-field dependences of absorption spectra are studied. Calculated spectra are compared with experimental observations in the literature, and correspondences of signatures are found. The deficiency and the potential of the present model are discussed.