Moir\'e-trapped interlayer trions in a charge-tunable WSe$_2$/MoSe$_2$ heterobilayer

TL;DR

This study uncovers how moiré patterns in WSe₂/MoSe₂ heterobilayers trap interlayer excitons and trions, revealing their spin configurations, interactions, and tunability via gating, advancing understanding of quantum emitters in 2D materials.

Contribution

It demonstrates the continuous evolution of interlayer excitons from isolated to ensemble states and identifies the origin of emission features, including moiré-trapped trions, in a charge-tunable heterobilayer.

Findings

Observation of trapped interlayer excitons with spin configurations.

Identification of narrow quantum-dot-like and broad ensemble emissions.

Formation of localized negative trions with distinct spin-valley states.

Abstract

Transition metal dichalcogenide heterobilayers offer attractive opportunities to realize lattices of interacting bosons with several degrees of freedom. Such heterobilayers can feature moir\'e patterns that modulate their electronic band structure, leading to spatial confinement of single interlayer excitons (IXs) that act as quantum emitters with $C_3$ symmetry. However, the narrow emission linewidths of the quantum emitters contrast with a broad ensemble IX emission observed in nominally identical heterobilayers, opening a debate regarding the origin of IX emission. Here we report the continuous evolution from a few trapped IXs to an ensemble of IXs with both triplet and singlet spin configurations in a gate-tunable $2H$-MoSe$_2$/WSe$_2$ heterobilayer. We observe signatures of dipolar interactions in the IX ensemble regime which, when combined with magneto-optical spectroscopy, reveal that the narrow quantum-dot-like and broad ensemble emission originate from IXs trapped in moir\'e potentials with the same atomic registry. Finally, electron doping leads to the formation of three different species of localised negative trions with contrasting spin-valley configurations, among which we observe both intervalley and intravalley IX trions with spin-triplet optical transitions. Our results identify the origin of IX emission in MoSe$_2$/WSe$_2$ heterobilayers and highlight the important role of exciton-exciton interactions and Fermi-level control in these highly tunable quantum materials.