On Spin 1/2 Excitations and Quantum Criticality in Two Dimensional O(3) Antiferromagnets

TL;DR

This paper demonstrates that 2+1 D quantum antiferromagnets with N´eel order host spin 1/2 excitations called spinons, which are skyrmions, and links quantum criticality to skyrmion gap collapse.

Contribution

It reveals that spinons in 2D antiferromagnets are skyrmions and connects skyrmion dynamics to quantum critical behavior without relying on Hopf or Berry phase terms.

Findings

Spinons are skyrmion excitations in the N´eel ordered phase.

Quantum criticality involves skyrmion gap collapse.

Skyrmions may be relevant for fractionalization at criticality.

Abstract

We show that despite the absence of a Hopf term and zero Berry phase terms, the N`eel ordered phase of 2+1 D quantum antiferromagnets have spin 1/2 excitations, i.e. spinons. The spinons are skyrmion excitations of a topological nature. Since skyrmion gap is proportional to the spin stiffness, quantum criticality corresponds to skyrmion gap collapse. We speculate that skyrmions are relevant at criticality and are, perhaps, related to recent suggestions of critical fractionalization.