Observation of strong electron dephasing in disordered Cu${}_{93}$Ge${}_4$Au${}_3$ thin films

We report the observation of strong electron dephasing in a series of disordered Cu${}_{93}$Ge${}_4$Au${}_3$ thin films. A very short electron dephasing time possessing very weak temperature dependence around 6 K, followed by an upturn with further decrease in temperature below 4 K, is found. The upturn is progressively more pronounced in more disordered samples. Moreover, a ln$T$ dependent, but high-magnetic-field-insensitive, resistance rise persisting from above 10 K down to 30 mK is observed in the films. These results suggest a nonmagnetic dephasing process which is stronger than any known mechanism and may originate from the coupling of conduction electrons to dynamic defects.