Spin-Polarized-Current State of Electrons in Bilayer Graphene

TL;DR

This paper introduces a model for spin-polarized-current states in bilayer graphene that explains various experimental observations, predicts a ferrimagnetic ground state near charge neutrality, and suggests spin-polarized Hall currents.

Contribution

The paper presents a novel theoretical model that accounts for experimental puzzles in bilayer graphene and predicts a ferrimagnetic ground state with spin-polarized Hall currents.

Findings

Energy gap can be closed by perpendicular electric field

Gap increases with magnetic field B

Ground state is ferrimagnetic near charge neutrality

Abstract

We propose a model of spin-polarized-current state for electrons in bilayer graphene. The model resolves the puzzles as revealed by experiments that (a) the energy gap $E_{\rm gap}$ of the insulating ground state at the charge neutrality point (CNP) can be closed by a perpendicular electric field of either polarity, (b) $E_{\rm gap}$ increases significantly with increasing the magnetic field $B$, (c) the particle-hole spectrum is asymmetric in the presence of $B$, (d) there is a peak structure in the electric conductivity at small $B$ at the CNP, and (e) there are quantum Hall states stemming from lifting of degeneracy in the lowest Landau level. The model predicts that the ground state of the system close to the CNP is a ferrimagnet at finite $B$ and the Hall current is spin polarized.