ABSTRACT
The V L Ginzburg-L D Landau theory is phenomenological: it is based on generally observed features of superconductivity and not on any particular microscopic model. The particular importance of the Ginzburg-Landau theory is that it describes regions in which the state of the superconductor is non-uniform such as the neighbourhoods of magnetic domain boundaries, quantized flux lines and surface superconductivity, regions of fluctuating superconductivity and proximity effect situations–many of which are technically important. The Landau theory was concerned with the free energy of a superconductor in a uniform state. Ginzburg and Landau introduced two new developments. The first was based on the success of the London equations, which seemed to show that a superconductor behaved as though governed by an effective wavefunction Ψ(r). Their second development, however, was to allow for the possibility that in a non-uniform situation the free energy might depend on the spatial derivatives of Ψ as well as on Ψ itself.
