Cylindrical Josephson junctions in magnetic fields
The radial Josephson current I/sub J/ between co-axial cylinders was measured as a function of axial and azimuthal magnetic fields. The junctions were of two types: 0.25 mm diameter Nb-oxide-Sn single junctions and 0.25 mm film diameter Nb-oxide-Sn film double junctions. The Sn film of the single junctions was 160 nm or 200 nm. The Sn films of the double junctions were both either 155 nm or 230 nm. For a pair of cylinders I/sub J/ is zero except when both members are in the same fluxoid quantum state. When I/sub J/not equal to O, the relative phase is independent of aximuthal angle theta. In all measurements the cylinders were in fluxoid state zero. There was a critical value of axial field B/sub s/ which destroyed the Josephson coupling for each junction. This critical field is smallest for the outer tin junction of the double junction. It depends upon geometry and film thickness but is independent of the value of I/sub J/. The calculated value of the Gibbs function per unit volume of the tin films is, however, nearly the same for all junctions at their respective critical fields. Th Josephson current for the 160 nm Sn film single cylindrical junction was measured as a function of axial field B/sub z/ and azimuthal field B/sub theta/. When the axial field was zero the Josephson current as a function of azimuthal field showed the Fraunhofer like pattern of a flat junction in a magnetic field. As the axial field was increased, the central lobe of the Fraunhofer pattern decreased and disappeared at the critical field leaving the side lobes broadened. It is well known that a Josephson junction may switch to the voltage state at any current less than the maximum Josephson current. For some cylindrical junctions the switching currents are not continuously distributed but discrete with certain values occurring repeatedly. This observation is not understood.
- Research Organization:
- Clemson Univ., SC (USA)
- OSTI ID:
- 6970139
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
656102 -- Solid State Physics-- Superconductivity-- Acoustic
Electronic
Magnetic
Optical
& Thermal Phenomena-- (-1987)
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
CHALCOGENIDES
CONFIGURATION
CURRENTS
CYLINDRICAL CONFIGURATION
DATA
DIMENSIONS
ELECTRIC CURRENTS
ELEMENTS
EXPERIMENTAL DATA
FILMS
INFORMATION
JOSEPHSON JUNCTIONS
JUNCTIONS
MAGNETIC FIELDS
METALS
NIOBIUM
NUMERICAL DATA
OXIDES
OXYGEN COMPOUNDS
SUPERCONDUCTING FILMS
SUPERCONDUCTING JUNCTIONS
THICKNESS
TIN
TRANSITION ELEMENTS