New skyrmions in the attractive Hubbard model with broken SO(4) symmetry

TL;DR

This paper predicts new skyrmion textures arising from symmetry breaking in the attractive Hubbard model, with implications for understanding topological excitations in correlated electron systems.

Contribution

It introduces novel skyrmion solutions linked to the pseudospin SU(2) symmetry breaking in the attractive Hubbard model, expanding the understanding of topological textures in such systems.

Findings

Existence of new skyrmion textures due to symmetry breaking.

Skyrmions unwrapping when doping away from half-filling.

Topological arguments support the presence of these textures.

Abstract

The coexistence of superconducting and charge-density-wave order in the half-filled attractive Hubbard model is interpreted as a consequence of the pseudospin SU(2) symmetry spontaneously broken to a `hidden' subgroup U(1). By topological arguments we show that there must exist new skyrmion textures associated with this symmetry breakdown. This fact is illustrated via a non-linear $\sigma$-model. Unlike the spin textures previously known in an antiferromagnetic background, doping the model away from half-filling leads the new skyrmions to unwrap.