Fluctuation-Induced Diamagnetism in Dirty Superconductors

An explicit evaluation is made of the fluctuation-induced diamagnetism from zeropoint fluctuations, which have been neglected in a previous calculation by Maki and Takayama. It is shown that in fact this contribution has another scaling field ~φ₀l², as calculated previously by Lee and Payne and by Kurkij\"arvi, Ambegaokar, and Eilenberger. However, this term gives rise to an almost constant susceptibility (of the same order as Landau diamagnetism) in the field region of experimental interest [i.e., H~Hc2(0), the upper critical field at $T=0$ K].