Experimental evidence for direct insulator-quantum Hall transition in multi-layer graphene
1 Department of Physics, National Taiwan University, Taipei 106, Taiwan
2 Graduate School of Advanced Integration Science, Chiba University, Chiba 263-8522, Japan
3 Department of Electrophysics, National Chiayi University, Chiayi 600, Taiwan
4 Department of Electrical Engineering, University at Buffalo, The State University of New York, Buffalo, NY 14206-1500, USA
5 Graduate Institute of Applied Physics, National Taiwan University, Taipei 106, Taiwan
Nanoscale Research Letters 2013, 8:214 doi:10.1186/1556-276X-8-214Published: 6 May 2013
We have performed magnetotransport measurements on a multi-layer graphene flake. At the crossing magnetic field Bc, an approximately temperature-independent point in the measured longitudinal resistivity ρxx, which is ascribed to the direct insulator-quantum Hall (I-QH) transition, is observed. By analyzing the amplitudes of the magnetoresistivity oscillations, we are able to measure the quantum mobility μq of our device. It is found that at the direct I-QH transition, μqBc ≈ 0.37 which is considerably smaller than 1. In contrast, at Bc, ρxx is close to the Hall resistivity ρxy, i.e., the classical mobility μBc is ≈ 1. Therefore, our results suggest that different mobilities need to be introduced for the direct I-QH transition observed in multi-layered graphene. Combined with existing experimental results obtained in various material systems, our data obtained on graphene suggest that the direct I-QH transition is a universal effect in 2D.