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

TL;DR

This study observes unusually strong and temperature-insensitive electron dephasing in disordered CuGeAu thin films, with a resistance increase at low temperatures likely due to dynamic defects affecting electron coherence.

Contribution

It reports the first observation of strong, nonmagnetic electron dephasing in disordered CuGeAu films, suggesting a new dephasing mechanism involving dynamic defects.

Findings

Electron dephasing time is very short and weakly temperature-dependent around 6 K.

Resistance increases logarithmically with decreasing temperature, insensitive to high magnetic fields.

Dephasing may originate from coupling of electrons to dynamic defects, not magnetic impurities.

Abstract

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.