High-frequency fluctuational conductivity in YBa₂Cu₃O_{7-δ}

We present measurements of the fluctuational excess conductivity at 48 GHz and 24 GHz in YBa$_{2}$Cu$_{3}$O$_{7-\delta}$ 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 $T_{c}$, 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.