Direct observation of the proliferation of ferroelectric loop domains and vortex-antivortex pairs

TL;DR

This study observes how ferroelectric domain patterns in hexagonal REMnO3 crystals evolve from stripe to vortex-antivortex configurations through thermal processes, revealing complex topological defect dynamics.

Contribution

It provides the first direct observation of the transition from stripe to vortex-antivortex domain patterns in ferroelectric materials, supported by experimental and simulation data.

Findings

Stripe domain patterns form below Tc in hexagonal REMnO3 crystals.

Stripe patterns turn into vortex-antivortex patterns after crossing Tc.

The transition involves topological defect dynamics consistent with the Kibble-Zurek Mechanism.

Abstract

We discovered "stripe" patterns of trimerization-ferroelectric domains in hexagonal REMnO3 (RE=Ho, ---, Lu) crystals (grown below ferroelectric transition temperatures (Tc), reaching up to 1435 oC), in contrast with the vortex patterns in YMnO3. These stripe patterns roughen with the appearance of numerous loop domains through thermal annealing just below Tc, but the stripe domain patterns turn to vortex-antivortex domain patterns through a freezing process when crystals cross Tc even though the phase transition appears not to be Kosterlitz-Thouless-type. The experimental systematics are compared with the results of our six-state clock model simulation and also the Kibble-Zurek Mechanism for trapped topological defects.