Nature of long-lived moir\'e interlayer excitons in electrically tunable MoS$_{2}$/MoSe$_{2}$ heterobilayers

TL;DR

This paper investigates the properties of long-lived interlayer excitons in MoS₂/MoSe₂ heterobilayers, revealing their formation at Brillouin zone edges, moiré-induced valley rule reversal, and potential for excitonic devices.

Contribution

It demonstrates that interlayer excitons are formed with negligible hybridization, exhibit moiré-induced valley rule reversal, and retain valley polarization for microseconds, advancing understanding of excitonic physics in heterobilayers.

Findings

Interlayer excitons form at Brillouin zone edges with minimal hybridization.

Moiré superlattice reverses valley-dependent optical selection rules.

Interlayer excitons have microsecond-long valley polarization retention.

Abstract

Interlayer excitons in transition-metal dichalcogenide heterobilayers combine high binding energy and valley-contrasting physics with long optical lifetime and strong dipolar character. Their permanent electric dipole enables electric-field control of emission energy, lifetime, and location. Device material and geometry impacts the nature of the interlayer excitons via their real- and momentum-space configurations. Here, we show that interlayer excitons in MoS$_{2}$/MoSe$_{2}$ heterobilayers are formed by charge carriers residing at the Brillouin zone edges, with negligible interlayer hybridization. We find that the moir\'e superlattice leads to the reversal of the valley-dependent optical selection rules, yielding a positively valued g-factor and cross-polarized photoluminescence. Time-resolved photoluminescence measurements reveal that the interlayer exciton population retains the optically induced valley polarization throughout its microsecond-long lifetime. The combination of long optical lifetime and valley polarization retention makes MoS$_{2}$/MoSe$_{2}$ heterobilayers a promising platform for studying fundamental bosonic interactions and developing excitonic circuits for optical information processing.