Effect of nonequilibrium quasiparticle flow on SNS Josephson junctions
Experiments have been carried out on the effect of a nonequilibrium flow of quasiparticles on the Josephson properties of a Ta-Cu-Ta SNS junction. A nonequilibrium quasiparticle flow can be set up at the junction because the thickness of the superconducting banks of the SNS sandwich is on the order of the depth to which the longitudinal electric field penetrates into the superconductor, and the sandwich is bracketed by thick plates of a normal metal. During the injection of quasiparticles into one of the superconducting banks of the SNS junction, Josephson generation is excited at the junction; the total current flowing across the junction is zero. The nonequilibrium quasiparticle current which flows across the SNS junction is several times the critical current I/sub c/ and has no direct effect on its Josephson characteristics. The appearance of a difference in the electrochemical potentials of the pairs and of Josephson generation at the junction is due exclusively to the flow of the superconducting current. The experimental results are analyzed on the basis of an equivalent circuit proposed for the junction by Kadin, Smith, and Skocpol (J. Low Temp. Phys. 38, 497 (1980)), simplified somewhat for the case at hand. A study of the temperature dependence of the effects shows that at T> or =0.97T/sub c/ the nonequilibrium quasiparticle current in the normal Josephson intermediate layer of the junction does not depend on Andreev reflection processes at the NS interfaces. The scale time for electron-phonon energy relaxation in the tantalum used as the superconductor is estimated to be tau/sub Epsilon/roughly-equal 4.0 x 10/sup -1/ s.
- Research Organization:
- Institute of Solid-State Physics, Academy of Sciences of the USSR
- OSTI ID:
- 5728670
- Journal Information:
- Sov. Phys. - JETP (Engl. Transl.); (United States), Journal Name: Sov. Phys. - JETP (Engl. Transl.); (United States) Vol. 62:4; ISSN SPHJA
- Country of Publication:
- United States
- Language:
- English
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Magnetic
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71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
COPPER
ELECTRON-PHONON COUPLING
ELECTRONIC CIRCUITS
ELEMENTS
EQUIVALENT CIRCUITS
JOSEPHSON JUNCTIONS
JUNCTIONS
METALS
PENETRATION DEPTH
QUASI PARTICLES
SUPERCONDUCTING JUNCTIONS
TANTALUM
TEMPERATURE DEPENDENCE
TRANSITION ELEMENTS