Continuum model study of optical absorption by hybridized moiré excitons in transition metal dichalcogenide heterobilayers

Yao-Wen Chang

Published 2023-04-26Version 1

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. Spin and valley degrees of freedom and related interactions are omitted in this model, except for the spin-orbit energy splitting of A and B excitons. In long moir\'e-wavelength and zero charge-transfer-coupling limits, the exciton model and the optical absorption formula can be reduced to the counterparts of an isolated exciton. 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.