Theory of Fluctuation-Induced Diamagnetism in Superconductors

Abstract

A free-energy expression for a pure superconductor is derived microscopically which includes effects of a nonlocal order parameter. In the presence of strong field the simple transformation $\stackrel{\ensuremath{\rightarrow}}{\mathrm{q}}\ensuremath{\rightarrow}\stackrel{\ensuremath{\rightarrow}}{\mathrm{q}}+\frac{2e\stackrel{\ensuremath{\rightarrow}}{\mathrm{A}}}{c}$ is no longer valid. Using this free energy, fluctuation-induced diamagnetism of a superconductor above ${T}_{c}$ is calculated. The resulting universal behavior for pure superconductors is in good agreement with the experiment of Gollub, Beasley, and Tinkham.