Ballistic edge states in Bismuth nanowires revealed by SQUID interferometry

TL;DR

This study demonstrates ballistic edge state transport in bismuth nanowires with spin-momentum locking, using SQUID interferometry, and shows magnetic field control of supercurrent phase due to high spin-orbit coupling.

Contribution

It reveals ballistic edge conduction in bismuth nanowires and demonstrates magnetic control of supercurrent phase, advancing understanding of topological edge states in heavy-element materials.

Findings

Ballistic edge transport observed in bismuth nanowires.

Magnetic field induces 0-pi transitions and phi0-junction behavior.

High g-factor and spin-orbit coupling enable phase manipulation.

Abstract

Spin-orbit interactions are known to have drastic effects on the band structure of heavy-element-based materials. Celebrated examples are the recently identified 3D and 2D topological insulators. In those systems transport takes place at surfaces or along edges, and spin-momentum locking provides protection against (non-magnetic) impurity scattering, favoring spin-polarized ballistic transport. We have used the measurement of the current phase relation of a micrometer-long single crystal bismuth nanowire connected to superconducting electrodes, to demonstrate that transport occurs ballistically along two edges of this high-spin-orbit material. In addition, we show that a magnetic field can induce to 0-pi transitions and phi0-junction behavior, thanks to the extraordinarily high g-factor and spin orbit coupling in this system, providing a way to manipulate the phase of the supercurrent-carrying edge states.