High-frequency fluctuational conductivity in YBa₂Cu₃O₇₋δ

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We present measurements of the fluctuational excess conductivity at 48 GHz and 24 GHz in YBa₂Cu₃O₇₋δ films above the transition temperature. The measurements depart from the gaussian prediction for finite-frequency fluctuational conductivity. We focus on the region not too close to Tc, where the real part of the excess conductivity drops much faster than the prediction of the gaussian model. We calculate the dynamic excess conductivity within a Ginzburg-Landau approach. In the calculation we insert a short-wavelength cutoff of the order of the inverse coherence length, in order to suppress high-momentum modes. The excess conductivity of all samples measured can be described very well by the modified model.