Exposing impostor Majorana zero modes through atomic-scale shot-noise

TL;DR

This paper demonstrates that atomic-scale shot-noise spectroscopy can reliably distinguish true Majorana zero modes from trivial bound states in superconductors, overcoming limitations of traditional conductance measurements.

Contribution

It introduces shot-noise spectroscopy as a new diagnostic tool to unambiguously identify Majorana zero modes and differentiate them from impostors in atomic-scale experiments.

Findings

Shot-noise measurements reveal the particle-hole character of zero-bias states.

Differential conductance peaks can be trivial, but shot-noise exposes their true nature.

Shot-noise spectroscopy reliably rules out false Majorana signatures.

Abstract

A robust zero-bias conductance peak in putative $p$-wave superconductors is often regarded as the primary signature of a Majorana zero mode. Yet similar features can also arise from trivial bound states. This ambiguity has limited the reliability of conventional spectroscopy as a diagnostic tool, raising a long-standing problem of how to detect such impostors. Here, we address this issue with an alternative approach, atomic-scale shot-noise spectroscopy, that goes beyond conductance measurements. Through a detailed investigation of multiple defect-bound zero-bias states in the widely studied superconductor Fe(Se,Te), we observe that differential conductance can exhibit an apparently `robust' zero-bias peak. However, shot-noise measurements consistently reveal the fingerprint of the individual particle- and hole character hidden in the tunnelling conductance, unambiguously exposing the trivial nature of the zero-bias peak. Our results establish shot-noise spectroscopy as a decisive diagnostic for ruling out false Majorana signatures in atomic-scale experiments.