2019/07/31 by Malte Kremser, Mauro Brotons-Gisbert, Johannes Knörzer +7 · 1 citation
Physics and Astronomy · #cond-mat.mes-hall #cond-mat.mtrl-sci #cond-mat.quant-gas #quant-ph
paper · pdf · doi:10.1038/s41699-020-0141-3
published as npj 2D Materials and Applications volume 4, Article number: 8 (2020) · 15 pages, 3 figures plus Supplementary Information (19 pages, 11 pages)
arxiv created 2020/06/24 · arxiv updated 2020/06/25
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 MoSe2-WSe2 hetero-bilayer (HBL) onto an array of SiO2 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 NIX∼1-5 via their power dependencies and directly measure the hierarchy of dipolar and exchange interactions as NIX increases. The interlayer biexciton (NIX=2) is found to be an emission doublet that is blue-shifted from the single exciton by ΔE=(8.4±0.6) meV and split by 2J=(1.2±0.5) meV. The blueshift is even more pronounced for triexcitons ((12.4±0.4) meV), quadexcitons ((15.5±0.6) meV) and quintexcitons ((18.2±0.8) 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 ℓ≈ 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.