High-quality Two-Dimensional Electron Gas in Undoped InSb Quantum Wells

TL;DR

This paper demonstrates high-mobility undoped InSb quantum wells with tunable electron gases, revealing detailed spin-orbit interactions, g-factor behavior, and quantum Hall phenomena, advancing understanding of quantum transport in these materials.

Contribution

It introduces undoped InSb quantum wells with record mobility and provides comprehensive transport characterization, including spin-orbit coupling and quantum Hall effects, which are novel in this material system.

Findings

Achieved electron mobility of 260,000 cm²/Vs at low density

Characterized spin-orbit interactions via weak antilocalization

Observed Ising quantum Hall ferromagnetism at ν=2

Abstract

We report on transport experiments through high-mobility gate-tunable undoped InSb QWs. Due to the elimination of any Si modulation doping, the gate-defined two-dimensional electron gases in the quantum wells display a significantly increased mobility of 260,000 cm$^2$/Vs at a rather low density of $2.4\times10^{11}$ cm$^{-2}$. Using magneto-transport experiments, we characterize spin-orbit interactions by measuring weak antilocalization. Furthermore, by measuring Shubnikov-de Haas oscillations in tilted magnetic fields, we find that the g-factor agrees with $k \cdot p$ theory calculations at low magnetic fields but grows with spin polarization and carrier density at high magnetic fields. Additionally, signatures of Ising quantum Hall ferromagnetism are found at filling factor $\nu$ = 2 for tilt angles where the Landau level energy equals the Zeeman energy. Despite the high mobility, the undoped InSb quantum wells exhibit no fractional quantum Hall effect up to magnetic fields of 25 T.