Long-lived direct and indirect interlayer excitons in van der Waals heterostructures

TL;DR

This study reveals long-lived interlayer excitons in MoSe2/WSe2 heterostructures, showing unique temperature and power behaviors, and introduces two types of interlayer excitons with different spatial and momentum characteristics.

Contribution

It uncovers the existence of two distinct interlayer excitons with long lifetimes and unusual properties, advancing understanding of excitonic states in van der Waals heterostructures.

Findings

Interlayer excitons exhibit long lifetimes up to 100 ns.

A doublet structure of interlayer excitons is observed.

Unusual temperature and power dependence of emission energy and linewidth.

Abstract

We investigate the photoluminescence of interlayer excitons in heterostructures consisting of monolayer MoSe2 and WSe2 at low temperatures. Surprisingly, we find a doublet structure for such interlayer excitons. Both peaks exhibit long photoluminescence lifetimes of several ten nanoseconds up to 100 ns at low temperatures, which verifies the interlayer nature of both. The peak energy and linewidth of both show unusual temperature and power dependences. In particular, we observe a blue-shift of their emission energy for increasing excitation powers. At a low excitation power and low temperatures, the energetically higher peak shows several spikes. We explain the findings by two sorts of interlayer excitons; one that is indirect in real space but direct in reciprocal space, and the other one being indirect in both spaces. Our results provide fundamental insights into long-lived interlayer states in van der Waals heterostructures with possible bosonic many-body interactions