Issue
EPL
Volume 80, Number 3, November 2007
Article Number 37007
Number of page(s) 5
Section Condensed Matter: Electronic Structure, Electrical, Magnetic and Optical Properties
DOI http://dx.doi.org/10.1209/0295-5075/80/37007
Published online 09 October 2007
EPL, 80 (2007) 37007
DOI: 10.1209/0295-5075/80/37007

Spin configurations and activation gaps of the quantum Hall states in graphene

T. Chakraborty1 and P. Pietiläinen1, 2

1  Department of Physics and Astronomy, University of Manitoba - Winnipeg, MB R3T 2N2, Canada
2  Department of Physical Sciences/Theoretical Physics, University of Oulu - P.O. Box 3000, FIN-90014, Finland

chakrabt@cc.umanitoba.ca

received 23 July 2007; accepted in final form 11 September 2007; published November 2007
published online 9 October 2007

Abstract
We report on our accurate evaluation of spin polarizations of the ground state and particle-hole gaps for the partially filled lowest Landau level, observed in recent experiments on graphene subjected to ultra-high magnetic fields. We find that the inter-electron interactions are important at these filling factors, characterized by the non-degenerate ground states and large particle-hole gaps at infinitely large wave vectors. The gaps are the largest for the quantum Hall states in the second Landau level. The weak appearence of quantum Hall plateaus in the experiments for certain filling factors in the second Landau level however indicates that at these filling factors, the system has a soft mode at a finite wave vector due presumably to the presence of disorder.

PACS
73.43.-f - Quantum Hall effects.
71.10.-w - Theories and models of many-electron systems.

© Europhysics Letters Association 2007