Quantum-Hall activation gaps in graphene.
We have measured the quantum-Hall activation gaps in graphene at filling factors nu=2 and nu=6 for magnetic fields up to 32 T and temperatures from 4 to 300 K. The nu=6 gap can be described by thermal excitation to broadened Landau levels with a width of 400 K. In contrast, the gap measured at nu=2 is strongly temperature and field dependent and approaches the expected value for sharp Landau levels for fields B>20 T and temperatures T>100 K. We explain this surprising behavior by a narrowing of the lowest Landau level.
Giesbers
A J M
AJ
High Field Magnet Laboratory, Institute for Molecules and Materials, Radboud University Nijmegen, Toernooiveld 7, 6525 ED Nijmegen, The Netherlands. J.Giesbers@science.ru.nl
Zeitler
U
U
Katsnelson
M I
MI
Ponomarenko
L A
LA
Mohiuddin
T M
TM
Maan
J C
JC