We report on the low frequency noise in the ballistic point-contacts between a silver tip and a niobium foil. The ballistic nature of the point-contacts is confirmed by Andreev reflection spectroscopy at low bias voltage with the Nb foil cooled below its superconducting transition temperature (Tc). We find that the voltage dependence of the low frequency noise differs for different point-contacts with varying contact resistances. At high bias voltages, random two level fluctuations appear and dominate over the background 1/f noise. From analysis of the Andreev reflection spectra, we show that such two level fluctuators may give rise to depairing of the superconducting order parameter.
@article{arxiv.1004.5451,
title = {Low frequency noise in ballistic Nb/Ag point contacts},
author = {Jian Wei and Goutam Sheet and Venkat Chandrasekhar},
journal= {arXiv preprint arXiv:1004.5451},
year = {2014}
}