Edge excitations of the canted antiferromagnetic phase of the ν=0 quantum Hall state in graphene: A simplified analysis

We perform a simplified analysis of the edge excitations of the canted antiferromagnetic (CAF) phase of the nu = 0 quantum Hall state in both monolayer and bilayer graphene. Namely, we calculate, within the framework of quantum Hall ferromagnetism, the mean-field quasiparticle spectrum of the CAF phase neglecting the modification of the order parameter at the edge. We demonstrate that, at a fixed perpendicular component B-perpendicular to of the magnetic field, the gap Delta(edge) in the edge excitation spectrum gradually decreases upon increasing the parallel component B-parallel to, as the CAF phase continuously transforms to the fully spin-polarized ferromagnetic (F) phase. The edge gap closes completely (Delta(edge) = 0) once the F phase, characterized by gapless counterpropagating edge excitations, is reached at some finite B-perpendicular to-dependent value B*(parallel to) and remains closed upon further increase of B-parallel to. This results in a gradual insulator-metal transition, in which the conductance G similar to (e(2)/h) exp(-Delta(edge)/T) grows exponentially with B-parallel to in the range 0 < B-parallel to < B*(parallel to) while in the gapped CAF phase, and saturates to a metallic value G similar to e(2)/h in the F phase at B-parallel to > B*(parallel to). This unique transport feature of the CAF phase provides a way to identify and distinguish it from other competing phases of the nu = 0 quantum Hall state in a tilted-field experiment.