Electron Glass in Ultrathin Granular Al Films at Low Temperatures

Abstract

Quench-condensed granular Al films, with normal-state sheet resistance close to 10 k$\Omega /\square$, display strong hysteresis and ultraslow, non-exponential relaxation in the resistance when temperature is varied below 300 mK. The hysteresis is nonlinear and can be suppressed by a dc bias voltage. The relaxation time does not obey the Arrhenius form, indicating the existence of a broad distribution of low energy barriers. Furthermore, large resistance fluctuations, having a 1/f-type power spectrum with a low-frequency cut-off, are observed at low temperatures. With decreasing temperature, the amplitude of the fluctuation increases and the cut-off frequency decreases. These observations combine to provide a coherent picture that there exists a new glassy electron state in ultrathin granular Al films, with a growing correlation length at low temperatures.

RevTeX 3.1, 4 pages, 4 figures (EPS files) (Minor Additions)

References in corpus (3)

• Time Dependent Development of the Coulomb Gap
• A possible new phase of commensurate insulators with disorder: the Mott Glass
• Observation of a Hard Correlation Gap in Quench-Condensed Ultrathin Beryllium

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