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Phys. Rev. Lett. 92, 066802 (2004) [4 pages]

Nonequilibrium Quasiparticles and 2e Periodicity in Single-Cooper-Pair Transistors

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J. Aumentado*, Mark W. Keller, and John M. Martinis
National Institute of Standards and Technology, Boulder, Colorado 80305-3337, USA

M. H. Devoret
Department of Applied Physics, Yale University, New Haven, Connecticut 06520-8284, USA

Received 14 May 2003; published 13 February 2004

We have fabricated single-Cooper-pair transistors in which the spatial profile of the superconducting gap energy was controlled by oxygen doping. The profile dramatically affects the switching current vs gate voltage curve of the transistor, changing its period from 1e to 2e. A model based on nonequilibrium quasiparticles in the leads explains our results, including the observation that even devices with a clean 2e period are “poisoned” by small numbers of these quasiparticles.

© 2004 The American Physical Society

URL:
http://link.aps.org/doi/10.1103/PhysRevLett.92.066802
DOI:
10.1103/PhysRevLett.92.066802
PACS:
73.23.Hk, 74.50.+r

*Electronic address: jose.aumentado@boulder.nist.gov