Tuning topological superconductivity in helical Shiba chains by supercurrent

TL;DR

This paper demonstrates that applying supercurrent to helical Shiba chains can induce and control topological superconducting phases, potentially enabling the observation and manipulation of Majorana states in experiments.

Contribution

It extends the microscopic model of magnetic atom chains on superconductors to include supercurrent effects, showing how supercurrent can tune topological phases and enhance the topological gap.

Findings

Supercurrent can transform gapless phases into topological gapped phases.

Supercurrent enables switching between trivial and topological phases.

Predictions are experimentally testable via STM for Majorana state control.

Abstract

Recent experimental investigations of arrays of magnetic atoms deposited on top of a superconductor have opened a new chapter in the search of topological superconductivity. We generalize the microscopic model derived by Pientka et al. [Phys. Rev. B \textbf{88}, 155420 (2013)] to accommodate the effects of finite supercurrent in the host material. Previously it was discovered that helical chains with nonplanar textures are plagued by a gapless phase. We show that by employing supercurrent it is possible to tune the chain from the gapless phase to the topological gapped phase. It is also possible to tune the chain between the trivial and the topological gapped phase, the size of which may be dramatically increased due to supercurrent. For planar textures supercurrent mainly contributes to proliferation of the gapless phase. Our predictions, which can be probed in STM experiments, are encouraging for observation and manipulation of Majorana states.