Abstract
Transition-metal dichalcogenide heterobilayers offer attractive opportunities to realize lattices of interacting bosons with several degrees of freedom. Such heterobilayers can feature moiré patterns that modulate their electronic band structure, leading to spatial confinement of single interlayer excitons (IXs) that act as quantum emitters with C3 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−MoSe2/WSe2 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 moiré potentials with the same atomic registry. Finally, electron doping leads to the formation of three different species of localized 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 MoSe2/WSe2 heterobilayers and highlight the important role of exciton-exciton interactions and Fermi-level control in these highly tunable quantum materials.Received 18 January 2021Revised 14 May 2021Accepted 9 June 2021DOI:https://doi.org/10.1103/PhysRevX.11.031033Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Research AreasExcitonsLuminescenceNanophotonicsPhysical Systems2-dimensional systemsQuantum dotsTransition metal dichalcogenidesCondensed Matter, Materials & Applied Physics
Highlights
Van der Waals heterobilayers consisting of vertically stacked monolayer transition-metal dichalcogenide semiconductors (TMDs) form atomically sharp interfaces with type-II band alignment [1,2]
The narrow emission linewidths of the quantum emitters contrast with a broad ensemble interlayer excitons (IXs) emission observed in nominally identical heterobilayers, opening a debate regarding the origin of IX emission
To understand the link between the individually resolved moire-trapped IXs and the ensemble IX emission, we focus on the power-dependent blueshifts observed in the PL energy of both IX0T and IX0S
Summary
Van der Waals heterobilayers consisting of vertically stacked monolayer transition-metal dichalcogenide semiconductors (TMDs) form atomically sharp interfaces with type-II band alignment [1,2]. The identification of the various neutral and charged exciton species provides new insight into multiple peaked IX spectra in heterobilayers, while the identification of the localized nature of the IX ensemble emission in MoSe2=WSe2 heterobilayers demonstrates the important role of the moirepotential in their magneto-optical properties. These findings highlight the necessity to consider the spatial pinning of the IXs to the moirelattice in order to achieve an accurate description of many-body excitonexciton phenomena in TMD heterobilayers
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