Influence of fluctuations on thermal conductivity of high-Tc YBa2Cu3O7−δ superconductor

To study a behavior of the thermal conductivity near Tc specific heat and thermal diffusivity of the YBa2Cu3O7−δ high-Tc ceramics were simultaneously measured. Close to Tc = 92.30 K the thermal diffusivity and the thermal conductivity discovered minima and the specific heat – maximum. Quantitative analysis of the influence of thermodynamical fluctuations showed the same power laws with Gaussian exponent equal to 0.5 and existing of crossover from the 3D Gaussian to 3D XY critical behavior in the specific heat and thermal conductivity at the approach to Tc. To explain the minimum in thermal conductivity at Tc we propose a mechanism of scattering of phonons on the superconducting fluctuations.