We report the observation of strong electron dephasing in a series of disordered ${\mathrm{Cu}}_{93}{\mathrm{Ge}}_4{\mathrm{Au}}_3$ 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.

• Received 15 November 2006

DOI:https://doi.org/10.1103/PhysRevLett.99.046601