Chiral CP^2 skyrmions in three-band superconductors

TL;DR

This paper demonstrates the existence of stable chiral $CP^2$ skyrmions in three-band superconductors with broken time reversal symmetry, which are energetically favorable or metastable and can serve as indicators of such symmetry breaking.

Contribution

It introduces and characterizes chiral $CP^2$ skyrmions as new topological defects in three-component superconductors with broken time reversal symmetry.

Findings

Chiral $CP^2$ skyrmions can be stable or metastable in three-band superconductors.

These skyrmions are energetically cheaper than vortices under certain conditions.

Observation of these defects indicates broken time reversal symmetry.

Abstract

It is shown that under certain conditions, three-component superconductors (and in particular three-band systems) allow stable topological defects different from vortices. We demonstrate the existence of these excitations, characterized by a $CP^2$ topological invariant, in models for three-component superconductors with broken time reversal symmetry. We term these topological defects "chiral $GL^{(3)}$ skyrmions", where "chiral" refers to the fact that due to broken time reversal symmetry, these defects come in inequivalent left- and right-handed versions. In certain cases these objects are energetically cheaper than vortices and should be induced by an applied magnetic field. In other situations these skyrmions are metastable states, which can be produced by a quench. Observation of these defects can signal broken time reversal symmetry in three-band superconductors or in Josephson-coupled bilayers of $s_\pm$ and s-wave superconductors.