Influence of a magnetic field on the two-dimensional phase transition in thin-film superconductors
This paper reports an experimental study of the influence of a magnetic field on the phase transition and low-temperature dynamical properties of two-dimensional superconducting films. Five samples of granular indium/indium oxide composite films were studied, with sheet resistances varying from 945 to 3150 ..cap omega../D'Alembertian, and thicknesses from 100 to 250 A. Measurements were made of the resistance R(T,H) and of the current-voltage characteristics in perpendicular magnetic fields of maximum value 30 G. The temperature range investigated ranged from 0.7T/sub c//sub 0/ to 1.5T/sub c//sub 0/, where T/sub c//sub 0/ is the Bardeen-Cooper-Schrieffer mean-field transition temperature. In the temperature regime above T/sub c/, the Kosterlitz-Thouless vortex unbinding temperature, the resistance was found to obey universal magnetic field scaling. Below T/sub c/, the magnetoresistance displayed an activated temperature dependence characteristic of vortex pinning. The pinning activation energy U(H,T) increased with a Ginzburg-Landau temperature dependence below T/sub c/ and displayed an unusual magnetic field dependence, varying inversely with magnetic field below 1 G, but becoming independent of field in stronger fields. As T/sub c/ was approached from below, all signs of vortex pinning disappeared, with U(H,T/sub c/) = 0 and the magnetoresistance exhibiting linear Bardeen-Stephen behavior. These results are interpreted in the context of other work on two-dimensional superconductors.
- Research Organization:
- Department of Physics Ohio State University, Columbus, Ohio 43210
- OSTI ID:
- 6293427
- Journal Information:
- Phys. Rev. B: Condens. Matter; (United States), Vol. 36:7
- Country of Publication:
- United States
- Language:
- English
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75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
INDIUM
MAGNETORESISTANCE
INDIUM OXIDES
SUPERCONDUCTING FILMS
GRANULAR MATERIALS
MAGNETIC FLUX
PHASE TRANSFORMATIONS
SUPERCONDUCTING COMPOSITES
TEMPERATURE DEPENDENCE
ULTRALOW TEMPERATURE
CHALCOGENIDES
COMPOSITE MATERIALS
ELECTRIC CONDUCTIVITY
ELECTRICAL PROPERTIES
ELEMENTS
FILMS
INDIUM COMPOUNDS
MATERIALS
METALS
OXIDES
OXYGEN COMPOUNDS
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360104* - Metals & Alloys- Physical Properties
360204 - Ceramics
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656100 - Condensed Matter Physics- Superconductivity