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Science 14 September 2007:
Vol. 317. no. 5844, pp. 1530 - 1533
DOI: 10.1126/science.1144359
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Reports

Phase-Coherent Transport in Graphene Quantum Billiards

F. Miao, S. Wijeratne, Y. Zhang,* U. C. Coskun,{dagger} W. Bao, C. N. Lau{ddagger}

As an emergent electronic material and model system for condensed-matter physics, graphene and its electrical transport properties have become a subject of intense focus. By performing low-temperature transport spectroscopy on single-layer and bilayer graphene, we observe ballistic propagation and quantum interference of multiply reflected waves of charges from normal electrodes and multiple Andreev reflections from superconducting electrodes, thereby realizing quantum billiards in which scattering only occurs at the boundaries. In contrast to the conductivity of conventional two-dimensional materials, graphene's conductivity at the Dirac point is geometry-dependent because of conduction via evanescent modes, approaching the theoretical value 4e2/{pi}h (where e is the electron charge and h is Planck's constant) only for short and wide devices. These distinctive transport properties have important implications for understanding chaotic quantum systems and implementing nanoelectronic devices, such as ballistic transistors.

Department of Physics and Astronomy, University of California at Riverside, Riverside, CA 92521, USA.

* Present address: School of Physical Science and Technology, Southwest University, Chongqing 400715, People's Republic of China.

{dagger} Present address: Department of Physics, Duke University, Durham, NC 27708, USA.

{ddagger} To whom correspondence should be addressed. E-mail: lau{at}physics.ucr.edu

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