Is spontaneous vortex generation in superconducting 4Hb-TaS$_2$ from vison-vortex nucleation with $\mathbb{Z}_2$ topological order?

TL;DR

This paper proposes that the spontaneous vortex generation observed in 4Hb-TaS$_2$ is due to vison-vortex nucleation associated with $ ext{Z}_2$ topological order, offering a new interpretation of experimental phenomena in this material.

Contribution

It introduces a novel mechanism linking $ ext{Z}_2$ topological order to vortex nucleation in 4Hb-TaS$_2$, expanding the understanding of topological phases in superconductors.

Findings

Spontaneous vortex generation explained by vison-vortex nucleation.

Distinct nucleation process between vortex lattice and vison crystal.

Proposed experiments to differentiate $ ext{Z}_2$ topological order from chiral spin liquids.

Abstract

We propose the superconducting van der Waals material 4Hb-TaS$_2$ to realize the $\mathbb{Z}_2$ topological order and interpret the recent discovery of the spontaneous vortex generation in 4Hb-TaS$_2$ as the vison-vortex nucleation. For the alternating stacking of metallic/superconducting and Mott insulating layers in 4Hb-TaS$_2$, we expect the local moments in the Mott insulating 1T-TaS$_2$ layer to form the $\mathbb{Z}_2$ topological order. The spontaneous vortex generation in 4Hb-TaS$_2$ is interpreted from the transition or nucleation between the superconducting vortex and the $\mathbb{Z}_2$ vison in different phase regimes. Differing from the single vison-vortex nucleation in the original Senthil-Fisher's cuprate proposal, we consider such nucleation process between the superconducting vortex lattice and the vison crystal. We further propose experiments to distinguish this proposal with the $\mathbb{Z}_2$ topological order from the chiral spin liquid scenarios.