近日，英国赫瑞瓦特大学的Brian D. Gerardot及其研究团队取得一项新进展。经过不懈努力，他们揭示了多轨道莫尔系统中场可调谐强关联态的相互作用。相关研究成果已于2024年1月30日在国际知名学术期刊《自然—物理学》上发表。

该研究团队在单层MoSe₂和双层2H WSe₂的异质结构中，发现了一种可调谐的相互作用，这种作用发生在由Γ-和K -衍生带容纳的强关联空穴态之间。研究人员深入研究了激子极化子的行为，并对层自由度和谷自由度进行了区分。他们发现，Γ带产生了一个由双轨哈伯德模型描述的电荷转移绝缘体。

当施加面外电场时，Γ和K衍生的能带会发生重新排列，载流子也会重新分布到层极化K轨道，从而产生魏格纳晶体和莫特绝缘态。此外，研究人员还观察到了与掺杂密度有关的相变相互作用的关联态。这些研究结果为进一步研究多轨道哈伯德模型哈密顿量提供了一个重要的平台。

据悉，在强关联体系中，电荷、自旋、晶格和轨道自由度的相互作用产生了各种独特的涌现现象。最近在过渡金属-二硫化物基莫尔条纹异质结构中观测到的关联相，可以用三角晶格单轨道哈伯德模型来描述。这个模型基于从布里渊区角（即所谓的K谷）推导出的莫尔条纹。而多轨道哈伯德模型则能描述更丰富的相图，这些相图可以用六角形晶格来描述，这些晶格在区域中心（称为Γ谷）具有莫尔条纹，或者考虑一个额外的层自由度。

附：英文原文

Title: The interplay of field-tunable strongly correlated states in a multi-orbital moiré system

Author: Campbell, Aidan J., Vitale, Valerio, Brotons-Gisbert, Mauro, Baek, Hyeonjun, Borel, Antoine, Ivanova, Tatyana V., Taniguchi, Takashi, Watanabe, Kenji, Lischner, Johannes, Gerardot, Brian D.

Issue&Volume: 2024-01-30

Abstract: The interplay of charge, spin, lattice and orbital degrees of freedom leads to a variety of emergent phenomena in strongly correlated systems. In transition-metal-dichalcogenide-based moiré heterostructures, recent observations of correlated phases can be described by triangular-lattice single-orbital Hubbard models based on moiré bands derived from the Brillouin-zone corners—the so-called K valleys. Richer phase diagrams described by multi-orbital Hubbard models are possible with hexagonal lattices that host moiré bands at the zone centre—called Γ valleys—or an additional layer degree of freedom. Here we report the tunable interaction between strongly correlated hole states hosted by Γ- and K-derived bands in a heterostructure of monolayer MoSe₂ and bilayer 2H WSe₂. We characterize the behaviour of exciton–polarons to distinguish the layer and valley degrees of freedom. The Γ band gives rise to a charge-transfer insulator described by a two-orbital Hubbard model. An out-of-plane electric field re-orders the Γ- and K-derived bands and drives the redistribution of carriers to the layer-polarized K orbital, generating Wigner crystals and Mott insulating states. Finally, we obtain degeneracy of the Γ and K orbitals at the Fermi level and observe interacting correlated states with phase transitions dependent on the doping density. Our results establish a platform to investigate multi-orbital Hubbard model Hamiltonians.

DOI: 10.1038/s41567-024-02385-4

Source: https://www.nature.com/articles/s41567-024-02385-4