Effect of ion irradiation induced defects on the excess conductivity of Cu1−xTlxBa2Ca1Cu2O8−δ superconductor thin films

The Cu1−xTlxBa2Ca1Cu2O8−δ superconductor thin film samples were bombarded with protons, Si and Au ions of energies 6, 20 and 20 MeV respectively using 5MV tandem pelletron accelerator at Experimental Physics Labs. Each un-irradiated sample had different values of normal state resistivity and the zero resistance critical temperature. The zero resistivity critical temperature has been increased after the irradiation by Si and Au ions. The fluctuation induced conductivity (FIC) analysis of the as-prepared and the ion irradiated samples were performed in the light of Aslamasov–Larkin (AL) theory. The FIC analysis has shown three dimensional (3D) fluctuations in the order parameter in all the samples along with a cross-over to two dimensional (2D) fluctuations at higher temperature. The 3D–2D cross-over temperature has been shifted to higher values after the ion irradiation. Moreover, a direct correlation between the zero resistivity critical temperature, 2D–3D cross-over temperature (TLD) and superconductivity fluctuation temperature (Tscf) was observed. These studies have shown that the fluctuation induced conductivity (excess conductivity) depends on the density of defects and is independent of their nature.

Research highlights► Excess conductivity analysis gives information about the dimensionality of the superconductor order parameter. ► The defects in crystals affect the microscopic properties of the superconductor materials. ► Excess conductivity has shown dependences on the defect density instead of their nature in CuTl-1212 superconductor thin films.