Excited state spectrum of strongly interacting magic-angle twisted bilayer graphene at three- quarters filling

Abstract

The interplay between strong electronic interaction and non-trivial topology in magic-angle twisted bilayer graphene (tBLG) yields many intriguing phenomena that range from superconductivity to a spontaneous quantum anomalous Hall state with Chern number ±1. WIth the equilibrium phase diagram under much scrutiny, a better theoretical understanding of the excitation spectrum of tBLG is crucial to reveal experimental signatures of competing phases and discern possible pathways of controlling their behavior out of equilibrium. To this end, we study an effective Wannier-orbital model from Kang and Vafek (2019) in the strong coupling limit, which captures the Chern state at three quarters filling as well as its competition with proximal stripe charge order. We compute the density and chiral excitation spectra as well as the charge gap as a function of the overlap of neighboring Wannier orbitals. Our results provide an experimental signature to detect the transition from the stripe phase to the Chern phase and offer insight into steering of the quantum anomalous Hall state via low-frequency driving.