Particle-hole symmetry and bifurcating ground-state manifold in the quantum Hall ferromagnetic states of multilayer graphene

作者：Toke Csaba^*

来源：Physical Review B, 2013, 88(24): 241411.

DOI：10.1103/PhysRevB.88.241411

The orbital structure of the quantum Hall ferromagnetic states in the zero-energy Landau level in chiral multilayer graphene (AB, ABC, ABCA, etc. stackings) is determined by the exchange interaction with all levels, including deep-lying states in the Dirac sea. This exchange field favors orbitally coherent states with a U(1) orbital symmetry if the filling factor nu is not a multiple of the number of layers. If electrons fill the orbital sector of a fixed spin/valley component to one-half, e.g., at nu = +/- 3, +/- 1 in the bilayer and at nu = +/- 2, +/- 6 in the ABCA four-layer, there is a transition to a Z(2) x U(1) manifold. For weak interaction, the structure in the zero-energy Landau band compensates for the different exchange interaction on the sublattices in the Landau orbitals; on the other side, the ground state comes in two copies that distribute charge on the sublattices differently. We expect a sequence of similar bifurcations in multilayers of Bernal stacking.