Moiré Patterns of Excitons in Twisted Bilayer Transition-Metal Dichalcogenides Heterostructure

Twisted van der Waals heterostructures and the corresponding superlattices, moiré patterns, have been regarded as remarkable platforms to modulate many-electron interactions and optical excitations of two-dimensional structures. We employ first-principles many-body perturbation theory to study excitons and their moiré patterns in twisted bilayer MoSe₂/WSe₂ heterostructures. Because of significant type-II band offsets of heterostructures, direct interlayer excitons are always the lowest-energy excitons. We find that the energy variation of interlayer excitons is more significant in the R-type twisting structures than that in the H-type ones. Moreover, although the electron-hole binding energy is nearly spatially homogenous, the optical oscillator strength and radiative lifetime of interlayer excitons are very sensitive to the local stacking style, and they can vary in a few orders of magnitude in different regions of twisted bilayer structures. As a result, optical moiré patterns of interlayer excitons with high contrasts of brightness and radiative lifetime are expected.