Noise-to-current ratio divergence as a fingerprint of dispersing Majorana edge modes

TL;DR

This paper proposes a definitive experimental signature for detecting dispersing Majorana edge modes in topological superconductors by measuring a divergence in the noise-to-current ratio, supported by analytical and numerical evidence.

Contribution

It introduces a novel noise-to-current ratio divergence as a fingerprint for dispersing Majorana modes, validated through analytical derivations and tight-binding numerical models.

Findings

Divergence in noise-to-current ratio indicates dispersing Majorana edge modes.

Analytical proof independent of specific superconductor models.

Numerical verification using tight-binding models.

Abstract

The definitive detection of Majorana modes in topological superconductors is a key issue in condensed matter physics. Here we propose a smoking-gun experiment for the detection of one-dimensional dispersing Majorana edge modes, based on theoretical results for multi-terminal transport in a setup consisting of two normal metal leads and a topological superconductor. In the proposed device, the unpaired nature of the Majorana edge modes inherently leads to the absence of the charge current in the linear response regime, while the current fluctuation remains significant. Therefore, the divergence in the noise-to-current ratio serves as unambiguous evidence for the presence of the dispersing Majorana edge modes. We reach this conclusion analytically, without relying on any specific model of topological superconductors. In addition, using tight-binding models of topological-insulator-based topological superconductors, we numerically verify the predicted divergent noise-to-current ratio. We also discuss the application of our proposal to the CoSi$_2$/TiSi$_2$ heterostructure and the iron-based superconductor FeTe$_{1-x}$Se$_x$.