Localization and interaction of interlayer excitons in MoSe$_2$/WSe$_2$ heterobilayers

TL;DR

This study investigates how interlayer excitons in MoSe2/WSe2 heterobilayers localize and interact, revealing defect and moiré potential traps, and identifies conditions for biexciton formation at various temperatures.

Contribution

It uncovers the origins of potential traps affecting exciton behavior and demonstrates the emergence of interlayer biexcitons under specific excitation and temperature conditions.

Findings

Identified defect and moiré potential traps affecting exciton localization.

Observed superlinear emission indicating biexciton formation.

Mapped temperature regimes for localized and delocalized excitons.

Abstract

Transition metal dichalcogenide (TMD) heterobilayers provide a versatile platform to explore unique excitonic physics via properties of the constituent TMDs and external stimuli. Interlayer excitons (IXs) can form in TMD heterobilayers as delocalized or localized states. However, the localization of IX in different types of potential traps, the emergence of biexcitons in the high-excitation regime, and the impact of potential traps on biexciton formation have remained elusive. In our work, we observe two types of potential traps in a MoSe$_2$/WSe$_2$ heterobilayer, which result in significantly different emission behavior of IXs at different temperatures. We identify the origin of these traps as localized defect states and the moir{\'e} potential of the TMD heterobilayer. Furthermore, with strong excitation intensity, a superlinear emission behavior indicates the emergence of interlayer biexcitons, whose formation peaks at a specific temperature. Our work elucidates the different excitation and temperature regimes required for the formation of both localized and delocalized IX and biexcitons, and, thus, contributes to a better understanding and application of the rich exciton physics in TMD heterostructures.