Vu DinhDuy, Das Sarma S
Condensed Matter Theory Center and Joint Quantum Institute, Department of Physics, University of Maryland, College Park, Maryland 20742, USA.
Phys Rev Lett. 2021 Jan 22;126(3):036803. doi: 10.1103/PhysRevLett.126.036803.
Inspired by the rich physics of twisted 2D bilayer moiré systems, we study Coulomb interacting systems subjected to two overlapping finite 1D lattice potentials of unequal periods through exact numerical diagonalization. Unmatching underlying lattice periods lead to a 1D bichromatic "moiré" superlattice with a large unit cell and consequently a strongly flattened band, exponentially enhancing the effective dimensionless electron-electron interaction strength and manifesting clear signatures of enhanced Mott gaps at discrete fillings. An important nonperturbative finding is a remarkable fine-tuning effect of the precise lattice commensuration, where slight variations in the relative lattice periods may lead to a suppression of the correlated insulating phase, in qualitative agreement with the observed fragility of the correlated insulating phase in twisted bilayer graphene. Our predictions, which should be directly verifiable in bichromatic optical lattices, establish that the competition between interaction and incommensuration is a key element of the physics of moiré superlattices.
受扭曲二维双层莫尔系统丰富物理学的启发，我们通过精确数值对角化研究了受到两个具有不等周期的重叠有限一维晶格势作用的库仑相互作用系统。底层晶格周期不匹配会导致具有大晶胞的一维双色“莫尔”超晶格，从而产生强烈扁平化的能带，指数增强有效无量纲电子 - 电子相互作用强度，并在离散填充时表现出增强的莫特能隙的清晰特征。一个重要的非微扰发现是精确晶格 commensuration 的显著微调效应，其中相对晶格周期的微小变化可能导致关联绝缘相的抑制，这与扭曲双层石墨烯中观察到的关联绝缘相的脆弱性在定性上一致。我们的预测应能在双色光学晶格中直接验证，它表明相互作用与非 commensuration 之间的竞争是莫尔超晶格物理学的关键要素。
