Near-zero-energy end states in topologically trivial spin-orbit coupled superconducting nanowires with a smooth confinement

TL;DR

This paper demonstrates that topologically trivial superconducting nanowires with smooth confinement can host near-zero energy end states, challenging the use of zero-bias peaks as definitive signatures of topological phases.

Contribution

It reveals that smooth confinement can produce near-zero energy states in trivial phases, complicating the interpretation of experimental signatures.

Findings

Smooth confinement leads to near-zero energy end states in trivial phases.

Zero-bias peaks are not exclusive indicators of topological superconductivity.

Topologically trivial nanowires can mimic Majorana signatures.

Abstract

A one-dimensional spin-orbit coupled nanowire with proximity-induced pairing from a nearby s-wave superconductor may be in a topological nontrivial state, in which it has a zero energy Majorana bound state at each end. We find that the topological trivial phase may have fermionic end states with an exponentially small energy, if the confinement potential at the wire's ends is smooth. The possible existence of such near-zero energy levels implies that the mere observation of a zero-bias peak in the tunneling conductance is not an exclusive signature of a topological superconducting phase even in the ideal clean single channel limit.