Unusual Landau levels in biased bilayer Bernal graphene

A generalized tight-binding model is employed to study how electrostatic gating influences the magnetoelectronic properties of a Bernal graphene bilayer. With the availability of the Landau wave function, the distribution among its sublattices enables detailed characterization of the Landau levels as well as their optical responses. The different electric potentials on respective layers break the interlayer symmetry, which in turn lifts the intervalley degeneracy. In addition, Landau levels in response to the bias field make direct crossings and anticrossings. The latter are manifestations of the noncrossing theorem: two states not distinguished by unique quantum numbers perform anticrossing with their wave function characteristics interchanged and strongly mixed near the point of anticrossing. Those significant changes are directly reflected in the magneto-optical spectra, including the splitting of absorption peaks and their enhancement or extinction in response to bias strength.