Triple-top-gate technique for studying the strongly interacting 2D electron systems in heterostructures

TL;DR

This paper introduces a triple-gate technique that significantly reduces contact resistance and enables detailed study of strongly interacting 2D electron systems in high-mobility heterostructures at millikelvin temperatures.

Contribution

The authors developed a novel triple-gate method that improves contact quality and allows exploration of electron solid behavior in ultra-high mobility heterostructures.

Findings

Reduced contact resistance in heterostructures

Observation of two-threshold voltage-current characteristics

Evidence for collective depinning and sliding of electron solid

Abstract

We have developed a technique that dramatically reduces the contact resistances and depletes a shunting channel between the contacts outside the Hall bar in ultra-high mobility SiGe/Si/SiGe heterostructures. It involves the creation of three overlapping independent gates deposited on top of the structure and allows transport measurements to be performed at millikelvin temperatures in the strongly interacting limit at low electron densities, where the energy of the electron-electron interactions dominates all other energy scales. This design allows one to observe the two-threshold voltage-current characteristics that are a signature for the collective depinning and sliding of the electron solid.