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Chaotic transport in bi-layer graphene quantum dots Y. Ochiai1, A. M. Mahjoub1, N. Aoki1, J. Song2, J. P. Bird2, D.F. Ferry3, Y. Kawano4, and K. Ishibashi4 1 Graduate School of Advanced Integration Science, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba, 263-8522, Japan 2 Department of Electrical Engineering, University at Buffalo, The State University of New York, Buffalo, NY 14216, USA 3 Department of Electrical Engineering, The Arizona State University, Tempe, AZ 85287-5706, USA 4 Advanced Device Laboratory, The Institute of Physical and Chemical Research (RIKEN), 2-1, Hirosawa, Wako, Saitama 351-0198, Japan The unique band-structure, and associated carrier properties, of graphene make this material of ideal interest for fundamental studies of quantum transport in low-dimensional systems, and for application as a broadly tunable sensor in the microwave and terahertz regimes. The gapless spectrum characteristic of single-layer graphene, as well as the small forbidden gap that appears in bilayer graphene, leads to quantum transport of Dirac fermions, in marked contrast to conventional semiconductors whose relevant band-gaps are typically several orders of magnitude larger. In this presentation, we describe the results of low-temperature studies of chaotic transport in bi-layer graphene, focusing on an analysis of the fractal magneto-resistance (MR) exhibited by these devices [1]. Indicative of quasi ballistic transport, the MR shows quantum-coherent conductance fluctuations that are similar to those typically exhibited by semiconductor quantum dots. Our studies suggest the formation of open quantum-dot structures in small graphene flakes, when they are contacted by sub-micron scale metal electrodes. Specifically, the fractal nature of the MR of these structures suggests that the basic transport properties can be related to the underlying quantization of the states of these open quantum-dots. [1] Y. Ujiie , S. Motooka , T. Morimoto , N. Aoki , D. K. Ferry , J. P. Bird and Y. Ochiai, J. Phys.: Condens. Matt. 21 (2009) 382202. |
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