Zero magnetic-field orbital vortices in s-wave spin-singlet superconductors

TL;DR

This paper predicts and demonstrates the theoretical existence of zero magnetic-field orbital vortices in two-dimensional s-wave spin-singlet superconductors, characterized by angular momentum-carrying supercurrents without net magnetic flux.

Contribution

It introduces a new type of vortex induced by spatial symmetry breaking, distinct from magnetic vortices, and provides a self-consistent theoretical framework for their stability and structure.

Findings

Orbital vortices can form in low-symmetry superconductors.

These vortices carry angular momentum without net magnetic flux.

The spatial distribution of the order parameter shows pronounced anisotropy.

Abstract

Breaking of time-reversal and point-group spatial symmetries can have a profound impact on superconductivity. One of the most extraordinary effects, due to the application of a magnetic field, is represented by the Abrikosov vortices with charged supercurrents circulating around their cores. Whether a similar phenomenon can be obtained by exploiting spatial symmetry breaking, e.g. through electric fields or mechanical strain, is a fundamentally relevant but not yet fully settled problem. Here, we show that in two-dimensional spin-singlet superconductors with unusually low degree of spatial symmetry content, vortices with supercurrents carrying angular momentum around the core can form and be energetically stable. The vortex has zero net magnetic flux since it is made up of counter-propagating Cooper pairs with opposite orbital moments. By solving self-consistently the Bogoliubov - de Gennes equations in real space, we demonstrate that the orbital vortex is stable and we unveil the spatial distribution of the superconducting order parameter around its core. The resulting amplitude has a characteristic pattern with a pronounced angular anisotropy that deviates from the profile of conventional magnetic vortices. These hallmarks guide predictions and proposals for the experimental detection.