Electrically tunable high-Chern-number quasiflat bands in twisted antiferromagnetic topological insulators

Isolated flat bands possessing high Chern numbers are highly prized in condensed matter physics. Here, the authors propose realizing high Chern number flat-band states through moir\'e engineering of the two coupled Dirac-cone surface states of antiferromagnetic topological insulator thin films. The emergent Dirac-cone states induced from the anisotropic intersurface couplings, respecting multifold rotational symmetries, are dubbed intertwined Dirac states. They are found to play a significant role in this process. Furthermore, topological phase transitions between trivial and nontrivial flat-band states can be tuned by an out-of-plane electric field.