Modulated interlayer exciton properties in a two-dimensional moiré crystal

Abstract

Twisted van der Waals heterostructures and the corresponding superlattices, moir\'e superlattices, are remarkable material platforms, in which electron interactions and excited-state properties can be engineered. Particularly, the band offsets between adjacent layers can separate excited electrons and holes, forming interlayer excitons that exhibit unique optical properties. In this work, we employ the first-principles GW-Bethe-Salpeter equation method to calculate quasiparticle band gaps, interlayer excitons, and their modulated excited-state properties in twisted $\mathrm{MoS}{\mathrm{e}}_{2}/\mathrm{WS}{\mathrm{e}}_{2}$ bilayers that are of broad interest currently. In addition to achieving good agreement with the measured interlayer exciton energies, we predict a more than 100-meV lateral quantum confinement on quasiparticle energies and interlayer exciton energies, guiding the effort on searching for localized quantum emitters and simulating the Hubbard model in two-dimensional twisted structures. Moreover, we find that the optical dipole oscillator strength and radiative lifetime of interlayer excitons are modulated by a few orders of magnitude across moir\'e supercells, highlighting the potential of using moir\'e crystals to engineer exciton properties for optoelectronic applications.