It is observed experimentally that the sign of the Hall resistance can be flipped by a dc electric current in the twisted bilayer graphene (TBG) at $3/4$ filling of the fourfold degenerate conduction flat bands. The experiment implies a switching of the valley polarization (VP) and topology in TBG. Here we present a theory on the current-induced switching of VP and topology. The presence of current in the bulk causes the redistribution of electron occupation in bands near the Fermi energy, which then deforms and shifts the band dispersion due to the Coulomb interaction. Above a critical current, the original occupied and empty bands can be swapped, resulting in the switching of VP and topology.

中文翻译：

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电流引起的扭曲双层石墨烯中异常霍尔电导的逆转

从实验上观察到，双绞层石墨烯（TBG）中的直流电流可将霍尔电阻的符号翻转为 $3/4$填充四倍简并的传导平坦带。该实验暗示了TBG中谷底极化（VP）和拓扑的切换。在这里，我们提出了一种关于电流引起的VP和拓扑切换的理论。体中电流的存在会导致电子在费米能附近的能带中重新分布，然后由于库仑相互作用而使能带的色散变形和移动。在临界电流以上，可以交换原始的占用频带和空频带，从而导致VP和拓扑结构的切换。