The Nature of Quantum Hall States near the Charge Neutral Dirac Point in Graphene

TL;DR

This study explores quantum Hall states near the charge neutral point in graphene, revealing their dependence on magnetic field orientation and suggesting a many-body origin for certain energy gaps.

Contribution

It provides new insights into the nature of QH states in graphene, especially their dependence on magnetic field components and degeneracy lifting mechanisms.

Findings

QH states at ν=±1 depend only on the perpendicular magnetic field component.

Activation energy gap at ν=1 shows non-linear magnetic field dependence.

Proposes that ν=0 and ±1 states result from lifting of degeneracies in the n=0 Landau level.

Abstract

We investigate the quantum Hall (QH) states near the charge neutral Dirac point of a high mobility graphene sample in high magnetic fields. We find that the QH states at filling factors $\nu=\pm1$ depend only on the perpendicular component of the field with respect to the graphene plane, indicating them to be not spin-related. A non-linear magnetic field dependence of the activation energy gap at filling factor $\nu=1$ suggests a many-body origin. We therefore propose that the $\nu=0$ and $\pm1$ states arise from the lifting of the spin and sub-lattice degeneracy of the $n=0$ LL, respectively.