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Science 6 April 2007:
Vol. 316. no. 5821, pp. 99 - 102
DOI: 10.1126/science.1139227
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Reports

Giant Fluctuations of Coulomb Drag in a Bilayer System

A. S. Price,1 A. K. Savchenko,1* B. N. Narozhny,2 G. Allison,1 D. A. Ritchie3

The Coulomb drag in a system of two parallel layers is the result of electron-electron interaction between the layers. We have observed reproducible fluctuations of the drag, both as a function of magnetic field and electron concentration, which are a manifestation of quantum interference of electrons in the layers. At low temperatures the fluctuations exceed the average drag, giving rise to random changes of the sign of the drag. The fluctuations are found to be much larger than previously expected, and we propose a model that explains their enhancement by considering fluctuations of local electron properties.

1 School of Physics, University of Exeter, Stocker Road, Exeter EX4 4QL, UK.
2 The Abdus Salam International Centre for Theoretical Physics, Strada Costiera 11, Trieste I-34100, Italy.
3 Cavendish Laboratory, University of Cambridge, Madingley Road, Cambridge CB3 0HE, UK.

* To whom correspondence should be addressed. E-mail: a.k.savchenko{at}ex.ac.uk

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Science. ISSN 0036-8075 (print), 1095-9203 (online)