Nonlinear current–voltage characteristics in electron doped YBCO superconductor below the critical temperature

Below the critical temperature, several Ce substituted YBa2Cu3O7−δ superconductors exhibit nonlinear current–voltage (IV) characteristics. We have extracted an exponent following the idea of the Kosterlitz–Thouless transition using IV over a wide range of temperatures around the critical temperature. The superfluid phase stiffness has been extracted within the framework of the Ambegaokar–Halperin–Nelson–Siggia theory. In a combined plot of the superfluid density and resistivity as a function of temperature, we observe that the superfluid density varies widely corresponding to the zero resistive states. The shift of the temperature corresponding to the crossing point with the electron doping level has been found to be very strong.