Ferroelectric and Multiferroic Properties of Quasi-2D Organic Charge-Transfer Salts

TL;DR

This review explores the ferroelectric and multiferroic properties of quasi-2D organic charge-transfer salts, emphasizing their electronic ferroelectricity driven by electronic correlations and recent experimental and theoretical advances.

Contribution

It provides a comprehensive overview of the physical properties, experimental evidence, and theoretical understanding of ferroelectricity and multiferroicity in strongly correlated charge-transfer salts.

Findings

Confirmation of electronic ferroelectricity in quasi-2D salts

Discovery of multiferroicity in these materials

Insights into magnetoelectric coupling mechanisms

Abstract

In conventional ferroelectrics the electric dipoles are generated by off-center displacements of ions. In recent years, a new type of so-called electronic ferroelectrics has attracted great attention, where the polarization is driven by electronic degrees of freedom. Of particular interest are materials with strong electronic correlations, featuring a variety of intriguing phenomena and instabilities, which may interact with or even induce electronic ferroelectricity. In this review, we will focus on the class of strongly correlated charge-transfer salts, where electronic ferroelectricity was suggested by theory and has been confirmed by numerous experiments. The paper summarizes some basic physical properties of various relevant quasi-two dimensional salts and gives some background on the experimental tools applied to establish ferroelectricity. We discuss the key experimental observations, including the exciting discovery of multiferroicity, and provide some theoretical considerations on the magnetoelectric couplings that are of relevance here.