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The interplay of charge, spin, lattice, and orbital degrees of freedom leads to a wide range of emergent phenomena in strongly correlated systems. In heterobilayer transition metal dichalcogenide moiré systems, recent observations of Mott insulators and generalized Wigner crystals are well described by triangular lattice single-orbital Hubbard models based on K-valley derived moiré bands. Richer phase diagrams, mapped onto multi-orbital Hubbard models, are possible with hexagonal lattices in Γ-valley derived moiré bands and additional layer degrees of freedom. Here we report the tunable interaction between strongly correlated hole states hosted by Γ- and K-derived moiré bands in a monolayer MoSe2 / natural WSe2 bilayer device. To precisely probe the nature of the correlated states, we optically characterise the behaviour of exciton-polarons and distinguish the layer and valley degrees of freedom. We find that the honeycomb Γ-band gives rise to a charge- transfer insulator described by a two-orbital Hubbard model with inequivalent ΓA and ΓB orbitals. With an out-of-plane electric field, we re-order the ΓB- and K-derived bands energetically, driving an abrupt redistribution of carriers to the layer-polarized K orbital where new correlated states are observed. Finally, by fine-tuning the band-alignment, we obtain degeneracy of the ΓB and K orbitals at the Fermi level. In this critical condition, stable Wigner crystals with carriers distributed across the two orbitals are observed until the Fermi-level reaches one hole per lattice site, whereupon the system collapses into a filled ΓB orbital. Our results establish a platform to investigate the interplay of charge, spin, lattice, and layer geometry in multi-orbital Hubbard model Hamiltonians.

権利情報:

• Creative Commons BY Attribution 4.0 International
  

キーワード: Strongly correlated systems, transition-metal-dichalcogenide, Hubbard models

刊行年月日: 2024-01-30

出版者: Springer Science and Business Media LLC

掲載誌:

• Nature Physics (ISSN: 17452481) vol. 20 issue. 4 p. 589-596

研究助成金:

原稿種別: 出版者版 (Version of record)

MDR DOI:

公開URL: https://doi.org/10.1038/s41567-024-02385-4

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更新時刻: 2025-02-23 22:48:53 +0900

MDRでの公開時刻: 2025-02-23 22:48:53 +0900