A Comparative Study Between Electro and Magneto Excess Conductivities in FeTeSe Superconductors

Abstract

We report here structural and fluctuation-induced excess conductivity in a FeTeSe superconductor by using the resistivity versus temperature measurements at different values of independent currents and applied fields (I = 1, 10, 50, and 100 mA, H = 0; H = 1, 3, 6, and 9 T, I = 10 mA). The prepared sample is investigated by using X-ray diffraction and standard four-probe technique using the resistivity option of PPMS-14 T. It was found that all peaks of the X-ray pattern are indexed as a tetragonal P4/nmm phase, and only a very small peak at about 2 𝜃 = 32.04∘ is obtained. The lattice parameters are a = b = 3.802(5) A and c = 6.070(2) A, and the medium size of crystallites is about 32 nm. Regardless of magnetic field for simplicity and by using Aslamazov and Larkin expression, the logarithmic plots of Δσ and reduced temperature (e), for both cases of different currents and fields, reveal three different conductivity exponents in the slope of each plot corresponding to two crossover temperatures. This is due to shifting of the order parameter dimensionality from short wave (SW) to two-dimensional/one-dimensional (2D/1D) and from 2D/1D to three-dimensional (3D), respectively. Furthermore, we estimated several physical parameters such as coherence lengths, Ginsburg number, anisotropy, G-L parameter, critical magnetic fields, and critical current density. Moreover, we follow Ullah and Dorsey field-dependent approximation for 3D and 2D analyses to obtain the fluctuation induced magneto-conductivity in the presence of magnetic field. Interestingly, the values of the slopes, deduced from logarithmic plots of 3D and 2D field dependence, are consistent with the values of SW conductivity exponents in the normal field region. In the mean field region, the values of the slopes for 3D are consistent with 2D conductivity exponents at H = 1, 3, and 6 T and with 1D at H = 9 T, while the values of the slopes for 2D are consistent with 3D conductivity exponents at H = 3, 6, and 9 T and with 1D at H = 1 T. As the field increases and keeping the temperature close to T c, the 3D curves seem to be slightly open like a fan, while the 2D curves are collapse together.