Broken-symmetry states and phase diagram of the lowest Landau level in bilayer graphene

TL;DR

This paper investigates the phase diagram and broken-symmetry states of the lowest Landau level in bilayer graphene, revealing how electric and magnetic fields influence quantum Hall states and their energy gaps.

Contribution

It provides a detailed analysis of the phase diagram and gap amplitudes of various quantum Hall states in bilayer graphene using the gap equation in the random phase approximation.

Findings

The critical line between spin and layer polarized phases extends to u=±1 states.

Gap amplitudes vary significantly among different filling factors.

Conductance minima correspond to the points where energy gaps are smallest.

Abstract

Broken-symmetry quantum Hall (QH) states with filling factors \nu=0, \pm 1, \pm 2, \pm 3 in the lowest Landau level in bilayer graphene are analyzed by solving the gap equation in the random phase approximation. It is shown that in the plane of electric and magnetic fields, the critical line, which separates the spin and layer polarized phases at \nu=0, extends to the \nu=\pm 1 QH states. The amplitudes of the gaps in the \nu= \pm 1, \pm 3, and \nu= \pm 2 QH states are significantly smaller than the amplitude of the \nu=0 gap, due to the separate filling of the n=0,1 orbital Landau levels and the negative contribution of the Hartree term, respectively. It is shown that those values of the external electric field where the conductance is not quantized correspond to the minima of the gaps.