Eur. Phys. J. B 27, 497-504 (2002)
https://doi.org/10.1140/epjb/e2002-00183-0

Frequency-dependent fluctuational conductivity above T_c in anisotropic superconductors: effects of a short wavelength cutoff

Dipartimento di Fisica “E. Amaldi” and Unità INFM, Università di Roma Tre, Via della Vasca Navale 84, 00146 Roma, Italy

Corresponding author: ^a silva@fis.uniroma3.it

Received: 19 March 2002
Published online: 25 June 2002

Abstract

We discuss the excess conductivity at nonzero frequencies in a superconductor above T_c within the Gaussian approximation. We focus the attention on the temperature range not too close to T_c: within a time-dependent Ginzburg-Landau formulation, we phenomenologically introduce a short wavelength cutoff (of the order of the inverse coherence length) in the fluctuational spectrum to suppress high momentum modes. We treat the general cases of thin wires, anisotropic thin films and anisotropic bulk samples. We obtain in all cases explicit expressions for the finite frequency fluctuational conductivity. The dc case directly follows. Close to T_c the cutoff has no effect, and the known results for Gaussian fluctuations are recovered. Above T_c, and already for , we find strong suppression of the paraconductivity as compared to the Gaussian prediction, in particular in the real part of the paraconductivity. At high ϵ the cutoff effects are dominant. We discuss our results in comparison with data on high-T_c superconductors.