Superconductance fluctuations in a normal channel: Dimensional crossovers
- Department of Applied Physics, Chalmers University of Technology University of Goeteborg, S-41296 Goeteborg (Sweden)
We study the excess conductance due to superconductance fluctuations of a metallic two-dimensional (2D) channel at temperatures slightly above the superconductor transition temperature. The conductance of a straight channel with arbitrary constant width [ital d] is computed. We find that the characteristic length scale [xi] depends on both temperature and frequency. The crossover from 1D (at [ital d][much lt][xi]) to 2D (at [ital d][much gt][xi]) behavior is characterized by a continuously varying effective dimensionality: 1[le][ital D][sub [ital e]]([ital d]/[xi])[le]2. For a channel with hyperbolic edges the results are similar, only the length of the channel is replaced by an effective length, which is logarithmic in the actual length. When a perpendicular magnetic field is applied, the excess conductance follows a scaling law with the number of vortices that fit in the area occupied by a fluctuating Cooper pair. The applied field induces a change in the effective dimensionality of the fluctuations. In a wide channel there is a direct crossover from 2D to 0D character. For a narrow channel, there is an intermediate regime, due to the formation of edge states, where the fluctuations are 1D. The length scale for this crossover depends on the temperature and the shift in [ital T][sub [ital c]] due to the field. The dependence of the transition temperature on the magnetic field is computed for arbitrary channel width. A dimensional crossover from 1D to 2D, as a function of the channel width, is observed. The characteristic length scale in this case is the radius of a vortex.
- OSTI ID:
- 5538837
- Journal Information:
- Physical Review, B: Condensed Matter; (United States), Vol. 48:21; ISSN 0163-1829
- Country of Publication:
- United States
- Language:
- English
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