Ultra-high quality two-dimensional electron systems

TL;DR

This paper reports a significant advancement in the quality of two-dimensional electron systems in GaAs quantum wells, achieving ultra-high mobility and revealing new quantum phenomena and states relevant for quantum computing.

Contribution

The authors developed improved sample fabrication techniques leading to unprecedented electron mobility and observed new quantum Hall states and phases.

Findings

Achieved electron mobility of 44 million cm^2/Vs

Observed robust stripe/bubble phases and new fractional quantum Hall states

Measured an activation gap of approximately 820 mK for the ν=5/2 state

Abstract

Two-dimensional electrons confined to GaAs quantum wells are hallmark platforms for probing electron-electron interaction. Many key observations have been made in these systems as sample quality improved over the years. Here, we present a breakthrough in sample quality via source-material purification and innovation in GaAs molecular beam epitaxy vacuum chamber design. Our samples display an ultra-high mobility of $44\times10^6$ cm$^2$/Vs at an electron density of $2.0\times10^{11}$ /cm$^2$. These results imply only 1 residual impurity for every $10^{10}$ Ga/As atoms. The impact of such low impurity concentration is manifold. Robust stripe/bubble phases are observed, and several new fractional quantum Hall states emerge. Furthermore, the activation gap of the $\nu=5/2$ state, which is widely believed to be non-Abelian and of potential use for topological quantum computing, reaches $\Delta\simeq820$ mK. We expect that our results will stimulate further research on interaction-driven physics in a two-dimensional setting and significantly advance the field.