Luo Xi-Wang, Zhang Chuanwei
Department of Physics, The University of Texas at Dallas, Richardson, Texas 75080-3021, USA.
Phys Rev Lett. 2021 Mar 12;126(10):103201. doi: 10.1103/PhysRevLett.126.103201.
Moiré superlattices in twisted bilayer graphene and transition-metal dichalcogenides have emerged as a powerful tool for engineering novel band structures and quantum phases of two-dimensional quantum materials. Here we investigate Moiré physics emerging from twisting two independent hexagonal optical lattices of atomic (pseudo-)spin states (instead of bilayers) that exhibit remarkably different physics from twisted bilayer graphene. We employ a momentum-space tight-binding calculation that includes all range real-space tunnelings and show that all twist angles θ≲6° can become magic and support gapped flat bands. Because of the greatly enhanced density of states near the flat bands, the system can be driven to superfluidity by weak attractive interaction. Strikingly, the superfluid phase corresponds to a Larkin-Ovchinnikov state with finite momentum pairing that results from the interplay between flat bands and interspin interactions in the unique single-layer spin-twisted lattice. Our work may pave the way for exploring novel quantum phases and twistronics in cold atomic systems.
扭曲双层石墨烯和过渡金属二卤化物中的莫尔超晶格已成为设计二维量子材料新颖能带结构和量子相的有力工具。在此，我们研究通过扭曲两个独立的原子（赝）自旋态六边形光学晶格（而非双层）所产生的莫尔物理，其展现出与扭曲双层石墨烯显著不同的物理特性。我们采用包含所有实空间隧穿范围的动量空间紧束缚计算，并表明所有扭转角θ≲6°都可成为魔角并支持带隙平带。由于平带附近态密度的大幅增强，该系统可通过弱吸引相互作用被驱动至超流态。引人注目的是，超流相对应于具有有限动量配对的拉金 - 奥夫钦尼科夫态，这是由独特单层自旋扭曲晶格中的平带与自旋间相互作用之间的相互作用所导致的。我们的工作可能为在冷原子系统中探索新颖量子相和扭曲电子学铺平道路。
