Formation of Long Single Quantum Dots in High Quality InSb Nanowires Grown by Molecular Beam Epitaxy

TL;DR

This study demonstrates the creation of highly tunable, high-quality InSb nanowire quantum dots via molecular beam epitaxy, revealing detailed electronic properties and potential for advanced quantum computing applications.

Contribution

It provides the first detailed transport spectroscopy analysis of MBE-grown InSb nanowire quantum dots, including size-dependent capacitance, level-dependent g-factors, and spin-orbit coupling strength.

Findings

Quantum levels are resolved in the few-electron regime.

Landé g-factors vary strongly with level, ranging from 18 to 48.

Spin-orbit coupling strength is approximately 300 μeV.

Abstract

We report on realization and transport spectroscopy study of single quantum dots (QDs) made from InSb nanowires grown by molecular beam epitaxy (MBE). The nanowires employed are 50-80 nm in diameter and the QDs are defined in the nanowires between the source and drain contacts on a Si/SiO$_2$ substrate. We show that highly tunable QD devices can be realized with the MBE-grown InSb nanowires and the gate-to-dot capacitance extracted in the many-electron regimes is scaled linearly with the longitudinal dot size, demonstrating that the devices are of single InSb nanowire QDs even with a longitudinal size of ~700 nm. In the few-electron regime, the quantum levels in the QDs are resolved and the Land\'e g-factors extracted for the quantum levels from the magnetotransport measurements are found to be strongly level-dependent and fluctuated in a range of 18-48. A spin-orbit coupling strength is extracted from the magnetic field evolutions of a ground state and its neighboring excited state in an InSb nanowire QD and is on the order of ~300 $\mu$eV. Our results establish that the MBE-grown InSb nanowires are of high crystal quality and are promising for the use in constructing novel quantum devices, such as entangled spin qubits, one-dimensional Wigner crystals and topological quantum computing devices.