Intrinsic electron-glassiness in strongly-localized Be films

TL;DR

This study demonstrates that strongly-localized beryllium films exhibit intrinsic electron-glass behavior, including slow relaxation and memory effects, with high carrier concentration identified as a key factor.

Contribution

First demonstration of intrinsic electron-glass behavior in beryllium films, highlighting high carrier concentration as a crucial factor for glassiness.

Findings

Beryllium films show slow (logarithmic) relaxation.

Memory effects and a characteristic memory dip observed.

High carrier concentration is a common feature in electron-glass systems.

Abstract

We present results of out--of-equilibrium transport measurements made on strongly-localized Beryllium films and demonstrate that these films exhibit all the earmarks of intrinsic electron-glasses. These include slow (logarithmic) relaxation, memory effects, and more importantly, the observation of a memory dip that has a characteristic width compatible with the carrier-concentration of beryllium. The latter is an empirical signature of the electron-glass. Comparing various non-equilibrium attributes of the beryllium films with other systems that exhibit intrinsic electron-glasses behavior reveals that high carrier-concentration is their only common feature rather than the specifics of the disorder that rendered them insulating. It is suggested that this should be taken as an important hint for any theory that attempts to account for the surprisingly slow relaxation times observed in these systems.