Landau Level Splitting in Graphene in High Magnetic Fields

TL;DR

This study explores the quantum Hall effect in high-quality graphene under strong magnetic fields, revealing Landau level splitting and new quantum Hall plateaus at high fields, advancing understanding of graphene's electronic properties.

Contribution

It reports the observation of Landau level splitting and new quantum Hall plateaus at high magnetic fields, providing insights into degeneracy lifting in graphene.

Findings

Discovery of QH plateaus at ν=0, ±1, ±4 above 20 T

Evidence of Landau level splitting at the Dirac point

Lifting of spin degeneracy in the n=1 Landau level

Abstract

The quantum Hall (QH) effect in two-dimensional (2D) electrons and holes in high quality graphene samples is studied in strong magnetic fields up to 45 T. QH plateaus at filling factors $\nu=0,\pm 1,\pm 4$ are discovered at magnetic fields $B>$20 T, indicating the lifting of the four-fold degeneracy of the previously observed QH states at $\nu=\pm(|n|+1/2)$, where $n$ is the Landau level index. In particular, the presence of the $\nu=0, \pm 1$ QH plateaus indicates that the Landau level at the charge neutral Dirac point splits into four sublevels, lifting sublattice and spin degeneracy. The QH effect at $\nu=\pm 4$ is investigated in tilted magnetic field and can be attributed to lifting of the spin-degeneracy of the $n=1$ Landau level.