  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 four-fold 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.
