Cooling low-dimensional electron systems into the microkelvin regime

TL;DR

This paper demonstrates cooling two-dimensional electron gases to below 1 millikelvin using liquid helium and nuclear adiabatic demagnetization, enabling exploration of correlated quantum states and topological phases.

Contribution

It introduces a novel cooling technique for 2DEGs to sub-millikelvin temperatures, facilitating studies of strongly correlated electron phenomena.

Findings

Achieved electron temperatures of 0.9 ± 0.1 mK.

Demonstrated effective cooling method with scope for improvement.

Enabled potential observation of new quantum phases.

Abstract

Two-dimensional electron gases (2DEGs) with high mobility, engineered in semiconductor heterostructures host a variety of ordered phases arising from strong correlations, which emerge at sufficiently low temperatures. The 2DEG can be further controlled by surface gates to create quasi-one dimensional systems, with potential spintronic applications. Here we address the long-standing challenge of cooling such electrons to below 1$\,$mK, potentially important for identification of topological phases and spin correlated states. The 2DEG device was immersed in liquid $^3$He, cooled by the nuclear adiabatic demagnetization of copper. The temperature of the 2D electrons was inferred from the electronic noise in a gold wire, connected to the 2DEG by a metallic ohmic contact. With effective screening and filtering, we demonstrate a temperature of 0.9$\,\pm\,$0.1$\,$mK, with scope for significant further improvement. This platform is a key technological step, paving the way to observing new quantum phenomena, and developing new generations of nanoelectronic devices exploiting correlated electron states.