https://doi.org/10.1140/epjb/e2002-00183-0
Frequency-dependent fluctuational conductivity above Tc 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
We discuss the excess conductivity at nonzero frequencies in a
superconductor above Tc within the Gaussian approximation. We focus the attention on the
temperature range not too close to Tc: 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 Tc
the cutoff has no effect, and the known results for Gaussian
fluctuations are recovered. Above Tc, 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-Tc superconductors.
PACS: 74.40.+k – Fluctuations (noise, chaos, nonequilibrium superconductivity, localization, etc.) / 74.20.De – Phenomenological theories (two-fluid, Ginzburg-Landau, etc.) / 74.25.Nf – Response to electromagnetic fields (nuclear magnetic resonance, surface impedance, etc.)
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 2002
