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Published April 1, 2006 | public
Journal Article Open

Universal point contact resistance between thin-film superconductors


A system comprising two superconducting thin films connected by a point contact is considered. The contact resistance is calculated as a function of temperature and film geometry, and is found to vanish rapidly with temperature, according to a universal, nearly activated form, becoming strictly zero only at zero temperature. At the lowest temperatures, the activation barrier is set primarily by the superfluid stiffness in the films, and displays only a weak (i.e., logarithmic) temperature dependence. The Josephson effect is thus destroyed, albeit only weakly, as a consequence of the power-law-correlated superconducting fluctuations present in the films below the Berezinskii-Kosterlitz-Thouless transition temperature. The behavior of the resistance is discussed, both in various limiting regimes and as it crosses over between these regimes. Details are presented of a minimal model of the films and the contact, and of the calculation of the resistance. A formulation in terms of quantum phase-slip events is employed, which is natural and effective in the limit of a good contact. However, it is also shown to be effective even when the contact is poor and is, indeed, indispensable, as the system always behaves as if it were in the good-contact limit at low enough temperature. A simple mechanical analogy is introduced to provide some heuristic understanding of the nearly activated temperature dependence of the resistance. Prospects for experimental tests of the predicted behavior are discussed, and numerical estimates relevant to anticipated experimental settings are provided.

Additional Information

©2006 The American Physical Society. Received 10 November 2005; published 4 April 2006. We are grateful to Leon Balents, Alexey Bezryadin, Arun Paramekanti, and Xiao-Gang Wen for useful discussions. This research was supported by the Department of Defense NDSEG program (M.H.); NSF Grant No. PHY99-07949 (G.R. and M.P.A.F.); NSF Grant No. DMR-0210790 (M.P.A.F.); and the U.S. Department of Energy, Division of Material Sciences under Grant No. DEFG02-91ER45439 (through the Frederick Seitz Materials Research Laboratory at UIUC) (P.M.G.).


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