Measurements of the superconducting fluctuations in optimally-doped BaFe$_{2-x}$Ni$_x$As$_2$ under high magnetic fields: Probing the 3D anisotropic Ginzburg-Landau approach

Abstract

The superconducting fluctuations well inside the normal state of Fe-based superconductors were experimentally studied through the in-plane paraconductivity in several high-quality optimally-doped BaFe 2−x Ni x As 2 crystals. These measurements were performed in magnetic fields with amplitudes up to 14 T, and different orientations relative to the crystals c axis (θ = 0 • , 53 • , and 90 • ). The results allowed a stringent check of the applicability of a recently proposed Ginzburg-Landau approach for the fluctuation electrical conductivity of 3D anisotropic materials in presence of finite applied magnetic fields.