On Temperature Dependence of Penetration Depth in Superconductors

By use of the Gorter-Casimir thermodynamic theory of superconductivity, the form of the Sommerfeld relation for the specific heat of electrons, and the form of the acceleration theory expression for penetration depth, the relative number of superconduction electrons and the relative penetration depth are derived as functions of the temperature. When the parabola relationship for threshold magnetic fields is used, comparison with experiment shows good agreement. In the limit of the absolute zero temperature, it is concluded that all of the normal conduction electrons become superconduction electrons in the absence of applied magnetic fields. The parabola relationship for threshold magnetic fields is discussed.