Order-disorder transitions in a polar vortex lattice

TL;DR

This study uses phase-field simulations to explore order-disorder transitions in polar vortex lattices within ferroelectric superlattices, revealing how interfacial coupling, strain, and periodicity influence vortex ordering.

Contribution

It uncovers the mechanisms of order-disorder transitions in polar vortex phases of ferroelectric superlattices, highlighting the roles of interfacial coupling and substrate strain.

Findings

Discovery of antiorder state in short periodicity superlattices

Transition from antiorder to disorder with increasing periodicity

Engineered order-disorder-antiorder transitions via substrate strain

Abstract

Order-disorder transitions are widely explored in various vortex structures in condensed matter physics, i.e., in the type-II superconductors and Bose-Einstein condensates. In this study, we have investigated the ordering of the polar vortex phase in the (PZT)n/(STO)n superlattice systems through phase-field simulations. An antiorder state is discovered for short periodicity superlattice on an SSO substrate, owing to the huge interfacial coupling between PZT and STO as well as the giant in-plane polarization in STO layers due to the large tensile strain. Increasing the periodicity leads to the anti-order to disorder transition, resulting from the loss of interfacial coupling and disappearance of the polarization in STO layers. On the other hand, for short periodicity superlattices, order-disorder-antiorder transition can be engineered by mediating the substrate strain, due to the delicate competition between the depoling effect, interfacial coupling, and strain effect. We envision this study to spur further interest towards the understanding of order-disorder transition in ferroelectric topological structures.