Collective depinning and sliding of a quantum Wigner solid in a 2D electron system

Abstract

We report the observation of two-threshold voltage-current characteristics accompanied by a peak of broadband current noise between the two threshold voltages in the insulating state at low densities in the 2D electron system in ultra-high mobility SiGe/Si/SiGe heterostructures. The observed results can be described by a phenomenological theory of the collective depinning of elastic structures, which naturally generates a peak of a broadband current noise between the dynamic and static thresholds and changes to sliding of the solid over a pinning barrier above the static threshold. This gives compelling evidence for the electron solid formation in this electron system and shows the generality of the effect for different classes of electron systems.