Modulated Interlayer Exciton Properties in a Two-Dimensional Moire Crystal

TL;DR

This paper uses first-principles calculations to explore how twisting bilayer MoSe2/WSe2 affects interlayer exciton properties, revealing significant energy modulation and potential for optoelectronic device engineering.

Contribution

It provides the first detailed theoretical analysis of modulated interlayer excitons in twisted 2D heterostructures using GW-BSE methods, including predictions of quantum confinement effects.

Findings

Over 100-meV lateral quantum confinement predicted

Optical dipole strength varies by orders of magnitude

Interlayer exciton energies agree with experiments

Abstract

Twisted van der Waals heterostructures and the corresponding superlattices, moire superlattices, are remarkable new 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 (BSE) method to calculate quasiparticle band gaps, interlayer excitons, and their modulated excited-state properties in twisted MoSe2/WSe2 bilayers that are of broad interest currently. In addition to achieving good agreements 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 moire supercells, highlighting the potential of using moire crystals to engineer exciton properties for optoelectronic applications.