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Experimental evidence for direct insulator-quantum Hall transition in multi-layer graphene

Chiashain Chuang12, Li-Hung Lin3, Nobuyuki Aoki2*, Takahiro Ouchi2, Akram M Mahjoub2, Tak-Pong Woo1, Jonathan P Bird24, Yuichi Ochiai2, Shun-Tsung Lo5 and Chi-Te Liang15*

Author affiliations

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

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Citation and License

Nanoscale Research Letters 2013, 8:214  doi:10.1186/1556-276X-8-214

Published: 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.

Insulator-quantum Hall transition; Graphene flake; Multi-layer graphene