Helical liquids and Majorana bound states in quantum wires

TL;DR

This paper demonstrates how spin-orbit coupling and magnetic fields can create helical liquids in quantum wires, leading to Majorana bound states with potential applications in topological quantum computing.

Contribution

It introduces a mechanism for forming helical liquids and Majorana bound states in quantum wires through combined effects of spin-orbit coupling, magnetic fields, and superconductivity.

Findings

Helical liquids can form in quantum wires with spin-orbit coupling and magnetic fields.

Majorana bound states emerge at wire regions with varying magnetic field, superconducting gap, or chemical potential.

Experimental signatures of these states are discussed.

Abstract

We show that the combination of spin-orbit coupling with a Zeeman field or strong interactions may lead to the formation of a helical liquid in single-channel quantum wires. In a helical liquid, electrons with opposite velocities have opposite spin precession. We argue that zero-energy Majorana bound states are formed in various situations when the wire is situated in proximity to a conventional s-wave superconductor. This occurs when the external magnetic field, the superconducting gap, or, in particular, the chemical potential vary along the wire. We discuss experimental consequences of the formation of the helical liquid and the Majorana bound states.