Anomalous thermal activation of the electron glass dynamics in a-InOx and granular aluminum

Abstract

In this article, we explore the temperature dependence of the electrical glassy dynamics in insulating amorphous indium oxide (a-InOx) and granular Al films. We use non-isothermal gate voltage protocols, which can reveal changes in the dynamics induced by the temperature, when logarithmic relaxations devoid of characteristic times are at work. We demonstrate that, contrary to almost 20 years of opposite belief, the dynamics of amorphous indium oxide films in the liquid helium temperature range is thermally activated, i.e. it slows down under cooling and accelerates upon heating. Amorphous indium oxide thus adds to the list of glassy disordered systems in which we already demonstrated thermal activation, which includes granular Al and amorphous NbxSi1-x films. Moreover, measurements up to 40 K in a-InOx and granular Al films reveal the close similarity between the two systems and a very anomalous character of the thermal activation, with an effective activation energy increasing with T as T^2 . We so far have no explanation for it. Its further study and understanding may be important for the physics of electron glasses.

To appear in the Journal of Physics Condensed Matter. The present version is the one originally submitted to the journal. Accepted manuscript : https://doi.org/10.1088/1361-648X/adeef7

References in corpus (15)

• Symmetrical field effect and slow electron relaxation in granular aluminium
• Relaxation dynamics in quantum electron-glasses
• Slow Dynamics of the Electron-Glasses; the Role of Disorder
• Memory effects in transport through a hopping insulator: Understanding two-dip experiments
• Intrinsic electron-glassiness in strongly-localized Be films
• Slow Conductance Relaxation in Insulating Granular Al: Evidence for Screening Effects
• Electron Glass in a three-dimensional system
• Coexistence of Electron-Glass Phase and Persistent Photoconductivity in GeSbTe Compounds
• Slow relaxation of conductance of amorphous hopping insulators
• Observation of thermally activated glassiness and memory dip in a-NbSi insulating thin films
• Nonequilibrium transport and Electron-Glass effects in thin GexTe films
• Evidence for thermal activation in the glassy dynamics of insulating granular aluminum conductance
• Electron glass effects in amorphous NbSi films
• Electron glass signatures up to room temperature in disordered insulators
• The effect of screening on the relaxation dynamics in the Coulomb glass