Eur. Phys. J. B 37, 277-284 (2004)
https://doi.org/10.1140/epjb/e2004-00057-5

Microwave fluctuational conductivity in YBa₂Cu₃O_7-δ

¹ Dipartimento di Fisica “E. Amaldi” and Unità INFM, Università “Roma Tre”, Via della Vasca Navale 84, 00146 Roma, Italy
² Dipartimento di Fisica and Unità INFM, Università “La Sapienza”, P.le Aldo Moro 2, 00185 Roma, Italy
³ Dipartimento di Fisica, Università di Salerno, Baronissi, Salerno, Italy

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

Received: 18 July 2003
Revised: 23 December 2003
Published online: 2 April 2004

Abstract

We present measurements of the microwave complex conductivity at 23.9 and 48.2 GHz in YBa₂Cu₃O_7-δ films, in the fluctuational region above T_c. With increasing temperature, the fluctuational excess conductivity drops much faster than the well-known calculations within the time-dependent Ginzburg-Landau theory [H. Schmidt, Z. Phys. 216, 336 (1968)]. Approaching the transition temperature, slowing down of the fluctuations is observed. We discuss the results in terms of a modified Gaussian theory for finite-frequency fluctuational conductivity, where renormalization is introduced in order to account for the regime, and a spectral cutoff is inserted in order to discard high-momentum modes. The data are in excellent agreement with the modified theory, when formulated for three-dimensional, anisotropic superconductors, in the whole experimentally accessible temperature range, and for both frequencies.