Tomasch effect and superconducting proximity

Journal Article · Wed Sep 01 00:00:00 EDT 1976 · J. Low Temp. Phys.; (United States)

DOI:https://doi.org/10.1007/BF00657173· OSTI ID:7335634

Nedellec, P ^[1]; Dumoulin, L; Guyon, E

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1. IBM Research Lab., San Jose, CA

Tunneling conductance measurements (dI/dV)(V) on thick and clean superconducting films (S/sub 1/) backed by normal metals (M/sub 2/) show geometrical resonance effects, which have been associated with the variation delta..delta..(x) of the pair potential near the interface. Analysis is made both theoretically and experimentally of the three factors involved in the resonance effect on S/sub 1//M/sub 2/ sandwiches where one of the films is superconducting. The first factor, period, has already received considerable attention and is connected with the ratio v*/sub F/d/sub 1/ of the renormalized Fermi velocity and the thickness d/sub 1/ of the film S/sub 1/. It is shown that generally subharmonic effects, related to multiple interference effects, are expected. This result is demonstrated experimentally on Pb/M/sub 2/ sandwiches. The phase depends on the sign of delta..delta..(x), the detailed shape of its variation, and on the nature of the tunneling process. Unfortunately the interplay among these parameters is difficult to analyze, although directive tunneling is found to fit better with experiments than the generally assumed diffuse tunneling. The amplitude of the resonance should be proportional to the change of delta..delta..(x). The ambiguity in the experimental results is pointed out and an experiment that shows clearly the role of the superconducting proximity mechanisms is described where the proximity on several simultaneously prepared Pb/Al films is controlled by deposition of various third upper layers. The theoretical discussion is an extension of the Ishii matrix formulation, itself based on an application of the Andreev scattering process.

• OSTI ID: 7335634
• Journal Information: J. Low Temp. Phys.; (United States), Vol. 24:5/6
• Country of Publication: United States
• Language: English

Related Subjects

75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
36 MATERIALS SCIENCE
ALUMINIUM
PROXIMITY EFFECT
LEAD
SUPERCONDUCTING FILMS
TUNNEL EFFECT
RESONANCE
ELEMENTS
FILMS
METALS
656102* - Solid State Physics- Superconductivity- Acoustic
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360104 - Metals & Alloys- Physical Properties