Chirality-driven ferroelectricity in LiCuVO$_4$

TL;DR

This paper provides experimental evidence of a vector chiral phase in LiCuVO$_4$, demonstrating chirality-driven ferroelectricity at temperatures above the multiferroic phase, highlighting a novel state in quantum magnets.

Contribution

It reports the first experimental identification of a vector chiral phase in LiCuVO$_4$, revealing chirality-driven ferroelectricity independent of long-range spin order.

Findings

Chiral phase persists above the multiferroic transition temperature.

Finite ferroelectric polarization indicates chiral order.

Chirality-driven ferroelectricity exists in a temperature window with suppressed spin order.

Abstract

Chirality or the handedness of objects is of prime importance in life science, biology, chemistry and physics. It is also a major symmetry ingredient in frustrated magnets revealing spin-spiral ground states. Vector chiral phases, with the twist (either clock- or counter clock-wise) between neighbouring spins being ordered, but with disorder with respect to the angles between adjacent spins, have been predicted almost five decades ago. Experimental proofs, however, are rare and controversial. Here, we provide experimental evidence for such a phase in LiCuVO$_4$, a one-dimensional quantum magnet with competing ferromagnetic and antiferromagnetic interactions. The vector chiral state is identified via a finite ferroelectric polarization arising at temperatures well above the multiferroic phase exhibiting long-range three-dimensional spin-spiral and polar order. On increasing temperatures, spin order becomes suppressed at TN, while chiral long-range order still exist, leaving a temperature window with chirality-driven ferroelectricity in the presence of an external magnetic field.