Ginzburg-Landau theory for superconductors

In this review the author describes how the simple Ginzburg-Landau approach lies in the heart of the general theory of superconductors. The reader is introduced to the handling of the theory and to the numerous possibilities of applications. A general free energy functional for a superconductor is given and the different cases where it can be reduced to a Ginzburg-Landau form or to a simple generalization of this form is studied. It is emphasized that applications are not restricted to thermo-dynamical ones as the Ginzburg-Landau approach can be used in the calculation of dissipative phenomena. The possibility of an extension to the time-dependent phenomena is discussed in detail to present the difficult problems which arise in that case. The gapless regime of type II superconductors is given as an example.