Noncollinear ferroelectric and screw-type antiferroelectric phases in a metal-free hybrid molecular crystal

TL;DR

This paper reports a novel organic salt exhibiting noncollinear electric dipole textures and a transition between ferroelectric and antiferroelectric phases, expanding understanding of noncollinear polarity in molecular crystals.

Contribution

It introduces a new organic salt with noncollinear electric dipoles and characterizes its phase transition, revealing unique noncollinear electric polarity phenomena.

Findings

Electric dipoles form noncollinear textures with 60° twisting.

The material exhibits a transition between ferroelectric and antiferroelectric phases.

Noncollinear electric polarity is demonstrated in a molecular crystal.

Abstract

Noncollinear dipole textures greatly extend the scientific merits and application perspective of ferroic materials. In fact, noncollinear spin textures have been well recognized as one of the core issues of condensed matter, e.g. cycloidal/conical magnets with multiferroicity and magnetic skyrmions with topological properties. However, the counterparts in electrical polarized materials are less studied and thus urgently needed, since electric dipoles are usually aligned collinearly in most ferroelectrics/antiferroelectrics. Molecular crystals with electric dipoles provide a rich ore to explore the noncollinear polarity. Here we report an organic salt (H2Dabco)BrClO4 (H2Dabco = N,N'-1,4-diazabicyclo[2.2.2]octonium) that shows a transition between the ferroelectric and antiferroelectric phases. Based on experimental characterizations and ab initio calculations, it is found that its electric dipoles present nontrivial noncollinear textures with $60^\circ$-twisting angle between the neighbours. Then the ferroelectric-antiferroelectric transition can be understood as the coding of twisting angle sequence. Our study reveals the unique science of noncollinear electric polarity.