Magnetic Properties of Superconducting Films
- 16 November 1964
- journal article
- research article
- Published by American Physical Society (APS) in Physical Review B
- Vol. 136 (4A) , A928-A937
- https://doi.org/10.1103/PhysRev.136.A928
Abstract
The general Gor'kov equations are solved for a superconducting film in a parallel magnetic field. The method determines the best pairing in the superconducting state without the need for ad hoc assumptions about pairing such as are used in other theories. The critical field and energy gap are determined for temperatures near the transition temperature at zero field . The energy gap in the quasiparticle excitation spectrum is shown to be approximately equal to the spatial average of the order parameter. For films whose thickness is less than the coherence length the Gor'kov equations are nonlocal and differ from the Ginzburg-Landau (GL) equations. In this range we find in agreement with experiment. For films with the solution of the Gor'kov equations are the same as the GL results, as expected, since this is a local regime. We find that for all (excepting ultrathin films) and in the temperature range the field dependence of the energy gap is the same as that given by the GL equations, i.e, . Thus, nonlocal effects do not change the field dependence of the gap. Most of the experimental data are in accord with this equation. However, some recent results for aluminum films show deviations which we interpret as probably being due to the important role played by energy-level quantization of single-particle states in ultrathin films. The extension of the method to lower temperatures and higher fields is also discussed.
Keywords
This publication has 21 references indexed in Scilit:
- Considerations on the Magnetic Field Problem in Superconducting Thin FilmsPhysical Review B, 1964
- Susceptibilities and Critical Fields of Superconducting FilmsPhysical Review B, 1963
- Shape resonances in superconductors - II simplified theoryPhysics Letters, 1963
- Effective Tunneling Density of States in SuperconductorsPhysical Review Letters, 1963
- Critical Field of Thin Superconducting ShapesPhysical Review B, 1962
- Critical Fields of Thin Superconducting Films. I. Thickness EffectsPhysical Review B, 1962
- Critical Field Measurements of Thin Superconducting Sn FilmsJournal of Applied Physics, 1962
- Size Effects in Thin Superconducting Indium FilmsPhysical Review B, 1961
- Theory of SuperconductivityPhysical Review B, 1957
- Evaluation of Some Nonlocal Theories for a Thin Superconducting FilmPhysical Review B, 1957