Short wavelength fluctuation effects on the magnetization in type I and low-k type II superconductors

• Published in: Journal of physics. Condensed matter 2003-05, Vol.15 (19), p.3283-3298
• Main Authors: Mosqueira, J, Carballeira, C, Curras, S R, Gonzalez, M T, Ramallo, M V, Ruibal, M, Torron, C, Vidal, F
• Format: Article
• Language: English
• ISSN: 0953-8984

The effects on the magnetization of fluctuating Cooper pairs created above the superconducting transition by thermal agitation energy (the so-called fluctuation-induced diamagnetism, FD) have been measured in a clean type I superconductor (Pb) and in a clean low Ginzburg-Landau parameter (*k) type II superconductor (Nb). These experiments extend the earlier measurements of Gollub, Beasley and Tinkham to both the high reduced temperature region (*e = ln(T/TC0) # > 0.1) and the high reduced magnetic field region (h = H/HC2(0) # > 0.1). Our data show that in spite of FD being deeply affected in both superconductors by the presence of non-local electrodynamic effects, the superconducting fluctuations sharply vanish when *e or h become of the order of 0.5 and, respectively, 1. This short-wavelength behaviour at high reduced temperatures of the superconducting fluctuations is similar to that previously observed at high reduced temperatures in dirty low-TC superconductors and in high-TC cuprates, where the non-local effects are unobservable. These last results suggest that in the short wavelength regime the superconducting fluctuations in clean low-TC superconductors are still dominated by the uncertainty principle, which imposes a limit to the shrinkage, when *e increases, of the superconducting wavefunction. This may also be the case when h RT 1, although the presence of strong non-local effects in these clean and low-*k superconductors may also deeply affect their high field behaviour.