Mai Peizhi, Zhao Jinchao, Feldman Benjamin E, Phillips Philip W
Department of Physics and Institute of Condensed Matter Theory, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA.
Geballe Laboratory of Advanced Materials, Stanford, CA, 94305, USA.
Nat Commun. 2023 Sep 26;14(1):5999. doi: 10.1038/s41467-023-41465-6.
In non-interacting systems, bands from non-trivial topology emerge strictly at half-filling and exhibit either the quantum anomalous Hall or spin Hall effects. Here we show using determinantal quantum Monte Carlo and an exactly solvable strongly interacting model that these topological states now shift to quarter filling. A topological Mott insulator is the underlying cause. The peak in the spin susceptibility is consistent with a possible ferromagnetic state at T = 0. The onset of such magnetism would convert the quantum spin Hall to a quantum anomalous Hall effect. While such a symmetry-broken phase typically is accompanied by a gap, we find that the interaction strength must exceed a critical value for this to occur. Hence, we predict that topology can obtain in a gapless phase but only in the presence of interactions in dispersive bands. These results explain the recent quarter-filled quantum anomalous Hall effects seen in moiré systems.
在非相互作用系统中，非平凡拓扑能带严格在半填充时出现，并表现出量子反常霍尔效应或自旋霍尔效应。在此，我们使用行列式量子蒙特卡罗方法和一个可精确求解的强相互作用模型表明，这些拓扑态现在转移到了四分之一填充。拓扑莫特绝缘体是其根本原因。自旋磁化率的峰值与T = 0时可能的铁磁态一致。这种磁性的出现会将量子自旋霍尔效应转变为量子反常霍尔效应。虽然这种对称性破缺相通常伴随着能隙，但我们发现相互作用强度必须超过一个临界值才能发生这种情况。因此，我们预测拓扑可以在无隙相中获得，但仅在色散能带中存在相互作用时才会出现。这些结果解释了最近在莫尔系统中观察到的四分之一填充量子反常霍尔效应。
