Fano resonances can provide two criteria to distinguish Majorana bound states from other candidates in experiments

TL;DR

This paper proposes two spectroscopic criteria involving symmetric zero-energy peaks and a 4π Josephson period to distinguish Majorana bound states from other phenomena in topological superconductors.

Contribution

It introduces a novel experimental setup with two STM tips to identify MBS using unique spectral features, providing clearer criteria for their detection.

Findings

Symmetric zero-energy peaks indicate Majorana fermions.

A 4π periodicity in the spectrum is a signature of MBS.

The criteria help differentiate MBS from impurities, Kondo effect, and Andreev states.

Abstract

There are still debates on whether the observed zero energy peak in the experiment by Stevan {\it et al.} [Science 346, 602(2014)] reveals the existence of the long pursuing Majorana bound states (MBS). we propose that, by mounting two scanning tunneling microscopic tips on top of the topological superconducting chain and measure the transmission spectrum between these two metallic tips, there are two kinds of characteristics on the spectrum that are caused by MBS uniquely. One is symmetric peaks with respect to zero energy and the other is $4\pi$ period caused by a nearby Josephson junction. The former refers to the fact that MBS are composited by Majorana fermions which distributed in the particle and hole subspaces equally. The latter is based on the well known $4\pi$ period of Josephson effect in topological superconductor. We think such two characteristics can be used as criteria to distinguish MBS from other candidates, such as impurities, Kondo effect and traditional Andreev bound states.