Theory of moir\'e localized excitons in transition-metal dichalcogenide heterobilayers

TL;DR

This paper investigates the localized exciton states induced by moiré patterns in transition-metal dichalcogenide heterobilayers, revealing their optical properties and symmetry-based selection rules through numerical modeling.

Contribution

It introduces a numerical approach to analyze moiré localized excitons, deriving their spectra, optical selection rules, and polarization-resolved absorption characteristics.

Findings

Localized excitons form deep, trigonal potential wells.

Optical response is dominated by doubly-degenerate $E$ states.

Derived optical selection rules based on $C_{3v}$ symmetry.

Abstract

Transition-metal dichalcogenide heterostructures exhibit moir\'e patterns that spatially modulate the electronic structure across the material's plane. For certain material pairs, this modulation acts as a potential landscape with deep, trigonally symmetric wells capable of localizing interlayer excitons, forming periodic arrays of quantum emitters. Here, we study these moir\'e localized exciton states and their optical properties. By numerically solving the two-body problem for an interacting electron-hole pair confined by a trigonal potential, we compute the localized exciton spectra for different pairs of materials. We derive optical selection rules for the different families of localized states, each belonging to one of the irreducible representations of the potential's symmetry group $C_{3v}$, and numerically estimate their polarization-resolved absorption spectra. We find that the optical response of localized moir\'e interlayer excitons is dominated by states belonging to the doubly-degenerate $E$ irreducible representation. Our results provide new insights into the optical properties of artificially confined excitons in two-dimensional semiconductors.