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arXiv · 1907.08815

Discrete Interactions between a few Interlayer Excitons Trapped at a MoSe$_2$-WSe$_2$ Heterointerface

Malte Kremser·Mauro Brotons-Gisbert·Johannes Knörzer·Janine Gückelhorn·Moritz Meyer·Matteo Barbone·Andreas V. Stier·Brian D. Gerardot·Kai Müller·Jonathan J. Finley
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Abstract

Interlayer excitons (IXs) in hetero-bilayers of transition metal dichalcogenides (TMDs) represent an exciting emergent class of long-lived dipolar composite bosons in an atomically thin, near-ideal two-dimensional (2D) system. The long-range interactions that arise from the spatial separation of electrons and holes can give rise to novel quantum, as well as classical multi-particle correlation effects. In order to acquire a detailed understanding of the possible many-body effects, the fundamental interactions between individual IXs have to be studied. Here, we trap a tunable number of dipolar within a nanoscale confinement potential induced by placing a MoSe$_2$-WSe$_2$ hetero-bilayer (HBL) onto an array of SiO$_2$ nanopillars. We control the mean occupation of the IX trap via the optical excitation level and observe discrete sharp-line emission from different configurations of interacting IXs. We identify these features as different multiparticle states with $N_{IX}\sim1-5$ via their power dependencies and directly measure the hierarchy of dipolar and exchange interactions as $N_{IX}$ increases. The interlayer biexciton ($N_{IX}=2$) is found to be an emission doublet that is blue-shifted from the single exciton by $\Delta E=(8.4\pm0.6)$ meV and split by $2J=(1.2\pm0.5)$ meV. The blueshift is even more pronounced for triexcitons ($(12.4\pm0.4)$ meV), quadexcitons ($(15.5\pm0.6)$ meV) and quintexcitons ($(18.2\pm0.8)$ meV). These values are shown to be mutually consistent with numerical modelling of dipolar excitons confined to a harmonic trapping potential having a confinement lengthscale in the range $\ell\approx 3$ nm. Our results contribute to the understanding of interactions between IXs in TMD HBLs at the discrete limit of only a few excitations and represent a key step towards exploring quantum correlations between them.

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Malte Kremser, Mauro Brotons-Gisbert, Johannes Knörzer, Janine Gückelhorn, Moritz Meyer, Matteo Barbone, Andreas V. Stier, Brian D. Gerardot, Kai Müller, Jonathan J. Finley. 2019-07-20. Discrete Interactions between a few Interlayer Excitons Trapped at a MoSe$_2$-WSe$_2$ Heterointerface. https://doi.org/10.1038/s41699-020-0141-3

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