Topological Phase Detection in Rashba Nanowires with a Quantum Dot

TL;DR

This paper proposes a method to detect topological phase transitions in Rashba nanowires with superconductivity by using a quantum dot to probe spin polarization, enabling phase identification without relying on Majorana states.

Contribution

It introduces a novel transport measurement technique using a quantum dot to identify topological phases in Rashba nanowires independently of Majorana bound states.

Findings

Quantum dot resonance reveals spin polarization of nanowire states.

Transport measurements can distinguish topological from trivial phases.

Method works independently of Majorana bound state detection.

Abstract

We study theoretically the detection of the topological phase transition occurring in Rashba nanowires with proximity-induced superconductivity using a quantum dot. The bulk states lowest in energy of such a nanowire have a spin polarization parallel or antiparallel to the applied magnetic field in the topological or trivial phase, respectively. We show that this property can be probed by the quantum dot created at the end of the nanowire by external gates. By tuning one of the two spin-split levels of the quantum dot to be in resonance with nanowire bulk states, one can detect the spin polarization of the lowest band via transport measurement. This allows one to determine the topological phase of the Rashba nanowire independently of the presence of Majorana bound states.