Boundary resistance of the superconducting-normal interface

Journal Article · Fri Feb 01 04:00:00 EST 1980 · Phys. Rev., B: Condens. Matter; (United States)

DOI:https://doi.org/10.1103/PhysRevB.21.945· OSTI ID:5691146

Hsiang, T Y; Clarke, J

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 T/sub c/, 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 T/sub c/ the resistance rose rapidly as the temperature was increased towards T/sub c/. 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 R/sub b/=Z (T)(Dtau/sub Q/*)/sup 1/2/rho/sub S//A, where Z (T) is a universal function of temperature, and D, tau/sub Q/*, rho/sub S/, 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 T/sub c/, the data are an excellent fit to the theory if one takes tau/sub Q/*=4k/sub B/Ttau/sub E/=0(T/sub c/)/..pi delta.. /sub infinity/ (T), where tau/sub E/=0(T/sub c/) is the inelastic-scattering time at the Fermi surface at T/sub c/, and ..delta.. /sub infinity/ (T) is the energy gap far from the interface.

• Research Organization: Ames Laboratory--United States Department of Energy and Department of Physics, Iowa State University, Ames, Iowa 50011
• OSTI ID: 5691146
• Journal Information: Phys. Rev., B: Condens. Matter; (United States), Journal Name: Phys. Rev., B: Condens. Matter; (United States) Vol. 21:3; ISSN PRBMD
• Country of Publication: United States
• Language: English

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36 MATERIALS SCIENCE
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75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ALLOYS
BISMUTH ALLOYS
COHERENCE LENGTH
DIFFUSION
ELECTRIC CONDUCTIVITY
ELECTRICAL PROPERTIES
ELEMENTS
ENERGY GAP
INDIUM
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LEAD ALLOYS
MEAN FREE PATH
METALS
PHYSICAL PROPERTIES
RELAXATION
SUPERCONDUCTING JUNCTIONS
TEMPERATURE DEPENDENCE
TIN
TIN ALLOYS