Electric field induced suppression of universal conductance fluctuations and dephasing in disordered systems

We report a novel phenomenon that the universal conductance fluctuations (UCF) can be suppressed by a small electric field E. The experiment has been carried out on single crystals of Si doped heavily with P and B beyond the critical composition of insulator to metal transition. The phenomenon is identified as a consequence of electric field induced dephasing of the electron wavefunction. Over the range of measurements, the observed dephasing rate (\tau_\phi^{-1}) varied as \tau_\phi^{-1} = aT + bE^q with q \approx 1.3 and for E >> E^*, a cross-over field, \tau_\phi^{-1} \sim E^q, independent of T. This experiment also establishes that the UCF can be utilized as a sensitive electron "interferometer" to measure dephasing rate.