Zero energy states clustering in an elemental nanowire coupled to a superconductor

TL;DR

This paper investigates how magnetic fields, weak disorder, and superconductivity in ultra-clean carbon nanotubes lead to low-energy state clustering, providing insights relevant for topological superconductivity research.

Contribution

It demonstrates that state clustering occurs in elemental nanowires under specific conditions, aligning with random matrix theory predictions, and highlights the need for alternative detection methods.

Findings

States cluster at low energy under combined magnetic field, disorder, and superconductivity.

Clustering behavior matches predictions from random matrix theory.

Phenomenology likely applies to various platforms aiming for topological superconductivity.

Abstract

Nanoelectronic hybrid devices combining superconductors and a one-dimensional nanowire are promising platforms to realize topological superconductivity and its resulting exotic excitations. The bulk of experimental studies in this context are transport measurements where conductance peaks allow to perform a spectroscopy of the low lying electronic states and potentially to identify signatures of the aforementioned excitations. The complexity of the experimental landscape calls for a benchmark in an elemental situation. The present work tackles such a task using an ultra-clean carbon nanotube circuit. Specifically, we show that the combination of magnetic field, weak disorder and superconductivity can lead to states clustering at low energy, as predicted by the random matrix theory predictions. Such a phenomenology is very general and should apply to most platforms trying to realize topological superconductivity in 1D systems, thus calling for alternative probes to reveal it.