Reentrant magic-angle phenomena in twisted bilayer graphene in integer magnetic fluxes

In this Letter we address the reentrance of magic-angle phenomena (band flatness and quantum-geometric transport) in twisted bilayer graphene (TBG) subjected to strong magnetic fluxes +/-(1)0, +/- 200, +/- 3(p0 ... ((D0 = h/e is the flux quantum per moire cell). The moire translation invariance is restored at the integer fluxes, for which we calculate the TBG band structure using accurate atomistic models with lattice relaxations. Similarly to the zero-flux physics outside the magic-angle condition, the reported effect breaks down rapidly with the twist. We conclude that the magic-angle physics reemerges in high magnetic fields, witnessed by the appearance of flat electronic bands distinct from Landau levels, and manifesting nontrivial quantum geometry. We further discuss the possible flat-band quantum geometric contribution to the superfluid weight in strong magnetic fields (28 T at 1.08 degrees twist), according to the Peotta-Torma mechanism [Nat. Commun. 6, 8944 (2015)].