Strongly correlated electronic states in a MoSe2/WSe2 moiré superlattice

2D transition metal dichalcogenide moiré superlattices have been shown to host hybrid excitonic states [1], localised quantum emitters [2] and tuneable correlated electronic states including Mott insulating and Wigner crystalline phases [3-5]. MoSe2/WSe2 heterostructures have been widely studied as a host of band-edge interlayer excitons. However, optical signatures of moiré flat band formation in these structures have thus far proved elusive. In this work we perform resonant absorption spectroscopy of intralayer excitons in a dual-gate tuneable MoSe2/WSe2 heterostructure with a 57.2o ± 0.3o twist angle at 4 K. We observe the formation of moiré intralayer excitons, as well as correlated electronic states at multiple fractional fillings of the first conduction and valence mini-bands. In the hole-doping regime, we observe the WSe2 charged exciton exhibits doping dependent extraordinary g-factors. We measure the magnetic phase diagram by tuning the fractional filling and observe a peak in the g-factor around 1 hole per moiré site. A Curie-Weiss fit to the temperature dependence of the g-factor at 1 hole per site suggests the formation of an anti-ferromagnetic Mott insulator. Our results show the potential of MoSe2/WSe2 heterostructures to probe a widely tunable, two-dimensional Hubbard system.
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2. H. Baek et al., Sci. Adv. 6, 37 (2020)
3. Y. Tang et al., Nature 579, 353 (2020)
4. E. Regan et al., Nature 579, 359 (2020)
5. Y. Xu et al., Nature 587 214 (2020)