Abstract
We have investigated the behavior of the resistance of graphene at the Landau level in an intense magnetic field . Employing a low-dissipation technique (with power ), we find that at low temperature , the resistance at the Dirac point undergoes a 1000-fold increase from to within a narrow interval of field. The abruptness of the increase suggests that a transition to an insulating ordered state occurs at the critical field . Results from five samples show that depends systematically on the disorder, as measured by the offset gate voltage . Samples with small display a smaller critical field . Empirically, the steep increase in fits accurately a Kosterlitz-Thouless-type correlation length over three decades. The curves of vs at fixed approach the thermal-activation form with a gap as , consistent with a field-induced insulating state.
2 More- Received 4 February 2009
DOI:https://doi.org/10.1103/PhysRevB.79.115434
©2009 American Physical Society