From multiferroics to cosmology: Scaling behaviour and beyond in the hexagonal manganites

TL;DR

This paper links the phase transition in hexagonal manganites to early-universe symmetry-breaking, applying Kibble-Zurek theory to predict defect formation and discovering unexpected anti-Kibble-Zurek behavior.

Contribution

It applies Kibble-Zurek theory to multiferroic hexagonal manganites, revealing new crossover phenomena and challenging existing understanding of defect formation.

Findings

Kibble-Zurek behavior is observed in hexagonal manganites.

Recent data align with theoretical predictions.

Discovery of anti-Kibble-Zurek behavior during crossover.

Abstract

We show that the improper ferroelectric phase transition in the multiferroic hexagonal manganites displays the same symmetry-breaking characteristics as those proposed in early-universe theories. We present an analysis of the Kibble-Zurek theory of topological defect formation applied to the hexagonal manganites, discuss the conditions determining the range of cooling rates in which Kibble-Zurek behavior is expected, and show that recent literature data are consistent with our predictions. We explore experimentally for the first time to our knowledge the cross-over out of the Kibble-Zurek regime and find a surprising "anti-Kibble-Zurek" behavior.