Paraconductivity of the K-doped SrFe2As2 superconductor

Paraconductivity of the optimally K-doped SrFe2As2 superconductor is investigated within existing fluctuation mechanisms. The in-plane excess conductivity has been measured in high-quality single crystals, with a sharp superconducting transition at Tc = 35.5 K and a transition width less than 0.3 K. The data have also been acquired in an external magnetic field up to 14 T. We show that the fluctuation conductivity data in zero field and for temperatures close to Tc can be explained within a three-dimensional (3D) Lawrence-Doniach theory, with a negligible Maki-Thompson contribution. In the presence of the magnetic field, it is shown that paraconductivity obeys the 3D Ullah-Dorsey scaling law, above 2 T and for H∥c. The estimated upper critical field and the coherence length nicely agree with the available experimental data. (paper)