Boundary resistance of the superconducting-normal interface

Thomas Y. Hsiang and John Clarke
Phys. Rev. B 21, 945 – Published 1 February 1980
PDFExport Citation

Abstract

The resistances of superconductor—normal-metal—superconductor sandwiches have been measured in which the mean free path of the superconductor was greater than or comparable with the coherence length. Below about 0.5 Tc, the resistance was nearly independent of temperature and, to within the experimental error, equal to the estimated resistance of the normal layer, indicating that there was relatively little interface contamination. At temperatures above about 0.9 Tc the resistance rose rapidly as the temperature was increased towards Tc. A theory for this rise, based on the normal metal-insulator-superconductor tunneling theory of Tinkham and Clarke, is used to calculate the quasiparticle charge imbalance, Q*, injected into the superconductor from the normal layer. The resultant additional boundary voltage per unit current is expressed as a boundary resistance Rb=Z(T)(DτQ*)12ρSA, where Z(T) is a universal function of temperature, and D, τQ*, ρS, and A are the electron diffusion coefficient, the charge relaxation time, the normal-state resistivity, and the cross-section area of the superconductor. Above 0.9 Tc, the data are an excellent fit to the theory if one takes τQ*=4kBTτE=0(Tc)πΔ(T), where τE=0(Tc) is the inelastic-scattering time at the Fermi surface at Tc, and Δ(T) is the energy gap far from the interface. The inferred values of τE=0(Tc) in Pb0.99Bi0.01, Sn, Sn0.99In0.01, and In, 0.25 × 1010 s, 2.6 × 1010 s, 1.1 × 1010 s, and 1.1 × 1010 s, respectively, are generally in good agreement with the computed values of Kaplan et al.

  • Received 6 August 1979

DOI:https://doi.org/10.1103/PhysRevB.21.945

©1980 American Physical Society

Authors & Affiliations

Thomas Y. Hsiang*

  • Ames Laboratory—U. S. DOE and Department of Physics, Iowa State University, Ames, Iowa 50011 and Department of Physics, University of California, Berkeley, California 94720 and Materials and Molecular Research Division, Lawrence Berkeley Laboratory, University of California, Berkeley, California 94720

John Clarke

  • Department of Physics, University of California, Berkeley, California 94720 and Materials and Molecular Research Division, Lawrence Berkeley Laboratory, University of California, Berkeley, California 94720

  • *Present address: Dept. of Phys., Ill. Institute of Tech. Chicago, Ill. 60616.

References (Subscription Required)

Click to Expand
Issue

Vol. 21, Iss. 3 — 1 February 1980

Reuse & Permissions
Access Options
Author publication services for translation and copyediting assistance advertisement

Authorization Required


×
×

Images

×

Sign up to receive regular email alerts from Physical Review B

Log In

Cancel
×

Search


Article Lookup

Paste a citation or DOI

Enter a citation
×