Meissner Effect and Flux Quantization in the Quasiparticle Picture

Abstract

A superconductor in a magnetic field is studied by means of a generalized quasiparticle transformation. Using the minimum principle for the thermodynamic grand potential, nonlinear equations are derived for the superconductor, which can be considered valid at finite temperature. For small magnetic potential these equations are linearized and shown to imply the London formula and the Meissner effect. For a multiply-connected superconductor the nonlinear equations are shown to be consistent with Maxwell's equation only if the magnetic flux is quantized in the units predicted by Onsager.