Frequency-dependent fluctuational conductivity above in anisotropic superconductors: effects of a short wavelength cutoff |
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Authors: | E Silva |
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Institution: | (1) Dipartimento di Fisica “E. Amaldi” and Unità INFM, Università di Roma Tre, Via della Vasca Navale 84, 00146 Roma, Italy, IT |
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Abstract: | 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 ε = ln(T/T
c) > 10-2, 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.
Received 19 March 2002 Published online 25 June 2002 |
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Keywords: | 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 ) |
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