# 2015 CAP Congress / Congrès de l'ACP 2015

13-19 June 2015
University of Alberta
America/Edmonton timezone
Welcome to the 2015 CAP Congress! / Bienvenue au congrès de l'ACP 2015!

## Chiral symmetry breaking and the quantum Hall effect in monolayer graphene

17 Jun 2015, 08:45
30m
NINT Taylor room (University of Alberta)

### NINT Taylor room

#### University of Alberta

Invited Speaker / Conférencier invité Condensed Matter and Materials Physics / Physique de la matière condensée et matériaux (DCMMP-DPMCM)

### Speaker

Prof. Malcolm Kennett (Simon Fraser University)

### Description

When graphene is placed in a strong magnetic field it exhibits quantum Hall states at fillings that can be predicted by taking into account the relativistic form of the low-energy electronic excitations and ignoring interactions between electrons. However, additional quantum Hall states are observed at filling fractions $\nu$ = 0 and $\nu$ = $\pm$1 that are not explained within a picture of non-interacting electrons. We propose that these states arise from interaction induced chiral symmetry breaking orders. We argue that when the chemical potential is at the Dirac point, weak onsite repulsion supports an easy-plane antiferromagnet state, which simultaneously gives rise to ferromagnetism oriented parallel to the magnetic field direction, whereas for $|\nu|$=1 easy-axis antiferromagnetism and charge-density-wave order coexist. We perform self-consistent calculations of the magnetic field dependence of the activation gap for the $\nu$ = 0 and $\nu$ = 1 states and obtain excellent agreement with recent experimental results. Funding: Supported by NSERC Reference: B. Roy, M. P. Kennett, and S. Das Sarma, Phys. Rev. B **90**, 201409(R) (2014).

### Primary author

Prof. Malcolm Kennett (Simon Fraser University)

 Slides