Dynamical Fluctuation of the Order Parameter and Diamagnetism of Superconductors. I. Dirty Limit

Limiting ourselves to dirty superconductors, we study theoretically the fluctuation-induced diamagnetism above the superconducting transition. We find that the dynamical fluctuation is extremely important except in the immediate vicinity of the transition region [i.e., T congruent to T-c(H) or H congruent to H-c2(T), where H-c2 is the upper critical field] and that this contribution does account for a large discrepancy between previous calculations and the recent experiment by Gollub, Beasley, and Tinkham.