Anisotropic non-split zero-energy vortex bound states in a conventional superconductor

TL;DR

This study reports the discovery of anisotropic non-split zero-energy vortex bound states in a conventional superconductor, challenging the assumption that such states are exclusive indicators of Majorana bound states in topological superconductors.

Contribution

It demonstrates that non-split zero-energy vortex states can occur in trivial superconductors, suggesting these states are not definitive signatures of Majorana quasiparticles.

Findings

Non-split zero-energy states observed in a conventional superconductor.

The states are influenced by surface electronic structure and quasiparticle trajectories.

Results imply non-split states are not exclusive evidence of Majorana bound states.

Abstract

Vortices in topological superconductors are predicted to host Majorana bound states (MBSs) as exotic quasiparticles. In recent experiments, the spatially non-split zero-energy vortex bound state in topological superconductors has been regarded as an essential spectroscopic signature for the observation of MBSs. Here, we report the observation of anisotropic non-split zero-energy vortex bound states in a conventional elemental superconductor with a topologically trivial band structure using scanning tunneling microscopy and spectroscopy. The experimental results, corroborated by quasi-classical theoretical calculations, indicate that the non-split states directly reflect the quasiparticle trajectories governed by the surface electronic structure. Our study implies that non-split zero-energy states are not a conclusive signature of MBSs in vortex cores, stimulating a revision of the current understanding of such states.