Stable quantum dots in an InSb two-dimensional electron gas

TL;DR

This paper demonstrates stable gate-defined quantum dots in InSb 2DEGs by removing the doping layer, enabling detailed studies of quantum confinement, spin states, and magnetic field effects in a material with high mobility and strong spin-orbit coupling.

Contribution

It introduces a novel method to create stable quantum dots in InSb 2DEGs by electrostatic carrier induction, overcoming previous charge instability issues.

Findings

Successful fabrication of stable quantum dots in InSb 2DEGs.

Observation of even-odd variation in addition energy.

Detection of singlet-triplet transition at low magnetic fields.

Abstract

Indium antimonide (InSb) two-dimensional electron gases (2DEGs) have a unique combination of material properties: high electron mobility, strong spin-orbit interaction, large Land\'{e} g-factor, and small effective mass. This makes them an attractive platform to explore a variety of mesoscopic phenomena ranging from spintronics to topological superconductivity. However, there exist limited studies of quantum confined systems in these 2DEGs, often attributed to charge instabilities and gate drifts. We overcome this by removing the $\delta$-doping layer from the heterostructure, and induce carriers electrostatically. This allows us to perform the first detailed study of stable gate-defined quantum dots in InSb 2DEGs. We demonstrate two distinct strategies for carrier confinement and study the charge stability of the dots. The small effective mass results in a relatively large single particle spacing, allowing for the observation of an even-odd variation in the addition energy. By tracking the Coulomb oscillations in a parallel magnetic field we determine the ground state spin configuration and show that the large g-factor ($\sim$30) results in a singlet-triplet transition at magnetic fields as low as 0.3 T.