Universal Conductance Fluctuations, Glassy Kinetics, and 1/F Noise.

The 1/f noise in strongly disordered metallic CCu and SiAu systems was studied in the temperature range 2-300 K. The temperature, frequency, and electric and magnetic field dependencies were found to be consistent with the predictions of the universal conductance fluctuation theory in the low temperature regime. Statistical properties of the noise in these systems were also studied in specially fabricated nanometer scale samples. Non-Gaussian effects and other aspects of the noise in these samples were used to probe the kinetics of the low energy excitations. In the range 4-30 K ample evidence was found of spectral features and 2 level and 3 level switching events with both tunneling and activated kinetics. This is the first observation of individual low energy excitations in amorphous metallic conductors. The noise in a majority of the systems exhibited anomalous non-Gaussian effects not consistent with a picture of randomly fluctuating independent two level systems.