Durability of the superconducting gap in Majorana nanowires under orbital effects of a magnetic field

TL;DR

This paper investigates how orbital effects of magnetic fields influence the superconducting gap in Majorana nanowires, revealing gap closure at experimentally relevant fields through a universal free energy minimization approach.

Contribution

It introduces a universal procedure for analyzing orbital effects in nanowires by minimizing free energy, applicable even with broken spatial symmetries, and demonstrates gap closure in strongly coupled systems.

Findings

Superconducting gap closes at magnetic fields consistent with experiments.

Orbital effects significantly influence the stability of Majorana nanowires.

The method accounts for broken spatial symmetries in the system.

Abstract

We analyze the superconducting gap in semiconductor/superconductor nanowires under orbital effects of a magnetic field in the weak- and strong-hybridization regimes using an universal procedure that guarantees the stationarity of the system -- vanishing of the supercurrent induced by spatially varying vector potential. We perform minimization of the free energy with respect to the vector potential which allows to account for the orbital effects even for systems with intrinsically broken spatial symmetries. For the experimentally relevant scenario of a strongly coupled semiconductor/superconductor, where the wave function of the charge carriers hybridizes between the two materials, we find that the gap closes due to the orbital effects in a sizable magnetic field compatible with the the recent experimental report [S. M. Albrecht, et al., Nature 531, 206 (2016)].