Electric noise properties of optimally doped Nd_1.85Ce_0.15CuO₄superconducting thin films

Abstract

Electric transport and voltage-noise-spectral-density measurements on Nd1.85Ce0.15CuO4 optimally doped thin films are reported. The samples have a good c-axis orientation, as revealed by detailed structural analysis. Superconductivity appears at a critical temperature K, a typical value reported for this compound. The noise properties evidence a quadratic current dependence of the 1/f component, indicating an origin due to resistance fluctuations. This is different from what is observed in disordered nonsuperconducting thin films, where evidence of unusual current dependences of 1/f noise has been found. While existing models are not able to quantitatively reproduce the temperature dependence of the observed 1/f noise in the resistive region, near Tc a simple percolation model describes well the experimental data.