Switchable polar spirals in tricolor oxide superlattices

TL;DR

This paper reports the discovery of switchable polar spiral structures in tricolor ferroelectric superlattices, exhibiting high thermal stability and reversible in-plane polarization switching, expanding the understanding of nanoscale topological ferroelectric states.

Contribution

The study introduces a new polar topological structure—ordered nanoscale spirals—in tricolor ferroelectric superlattices, with detailed phase field simulation analysis.

Findings

Polar spiral structures are composed of semivortex arrays with wavy vortex cores.

The system has an ultrahigh Curie temperature of 1000 K.

The spiral-to-orthorhombic phase transition occurs at 650 K.

Abstract

There are increasing evidences that ferroelectric states at the nanoscale can exhibit fascinating topological structures including polar vortices and skyrmions,akin to those observed in the ferromagnetic systems. Here we report the discovery of a new type of polar topological structure,ordered array of nanoscale spirals in the tricolor ferroelectric superlattice system via phase field simulations. This polar spiral structure is composed of fine ordered semivortex arrays with vortex cores forming a wavy distribution. It is demonstrated that this tricolor system has an ultrahigh Curie temperature of 1000 K and a temperature of 650 K for the phase transformation from spiral structure to inplane orthorhombic domain structure, showing a greatly enhanced thermal stability than the recently discovered polar vortex lattices in the superlattice system. Moreover, the spiral structure has a net inplane polarization that could be switched by an experimentally feasible irrotational inplane field. The switching process involves a metastable vortex state, and is fully reversible.