Berlin 2005 – scientific programme

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TT: Tiefe Temperaturen

TT 10: Superconductivity - Tunneling, Josephson Junctions, SQUIDs

TT 10.14: Talk

Saturday, March 5, 2005, 12:00–12:15, TU H104

Magnetoresistance of a mesoscopic DC SQUID — •Paul Goldbart, David Pekker, David Hopkins, and Alexey Bezryadin — Department of Physics, University of Illinois at Urbana-Champaign, 1110 West Green Street, Urbana, Illinois 61801-3080, U.S.A.

We analyze an all-superconducting mesoscopic DC SQUID, comprising a pair of thin-film strips connected by a pair of parallel ultra-narrow wires. We focus on the magnetoresistance of the device in the size range in which the strips are narrower than the penetration depth (i.e. the mesoscopic regime), and especially on the low-magnetic-field regime, in which no vortices are present in the strips. The resistance originates in dissipative order-parameter fluctuations in the wires, and its magnetic-field dependence comes from the phase-gradient of the order parameter in the strips, associated with screening currents. We present a theory of the magnetoresistance of this mesoscopic DC SQUID, based on the Langer-Ambegaokar-McCumber-Halperin theory of intrinsic resistance. We compare this theory with recent experimental data, and discuss why the device can be regarded as a superconducting phase gradiometer.