Twisted bilayer graphene (TBG) is remarkable for its topological flat bands, which drive strongly interacting physics at integer fillings, and its simple theoretical description facilitated by the Bistritzer-MacDonald Hamiltonian, a continuum model coupling two Dirac fermions. Because of the large moiré unit cell, TBG offers the unprecedented opportunity to observe reentrant Hofstadter phases in laboratory-strength magnetic fields near 25 T. This Letter is devoted to magic angle TBG at $2\pi$ flux where the magnetic translation group commutes. We use a newly developed gauge-invariant formalism to determine the exact single-particle band structure and topology. We find that the characteristic TBG flat bands reemerge at $2\pi$ flux, but, due to the magnetic field breaking $C_{2z}\mathcal{T}$, they split and acquire Chern number $\pm 1$. We show that reentrant correlated insulating states appear at $2\pi$ flux driven by the Coulomb interaction at integer fillings, and we predict the characteristic Landau fans from their excitation spectrum.

中文翻译：

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25 T (2πFlux) 下扭曲双层石墨烯中的重入相关绝缘体

扭曲双层石墨烯 (TBG) 因其拓扑平坦带而引人注目，该带驱动整数填充中的强相互作用物理，以及由 Bistritzer-MacDonald 哈密顿量（一种耦合两个狄拉克费米子的连续体模型）促进的简单理论描述。由于大型莫尔晶胞，TBG 提供了前所未有的机会，可以在 25 T 附近的实验室强度磁场中观察再入 Hofstadter 相。这封信专门讨论魔角 TBG$2\pi$磁平移组通勤的通量。我们使用新开发的规范不变形式来确定精确的单粒子能带结构和拓扑。我们发现特征 TBG 扁平带在$2\pi$通量，但是，由于磁场破坏$C_{2z}\mathcal{吨}$，他们分裂并获得陈数$\pm 1$. 我们表明，重入相关绝缘状态出现在$2\pi$由整数填充处的库仑相互作用驱动的通量，我们从激发光谱中预测了特征朗道风扇。