Relaxor ferroelectricity induced by electron correlations in a molecular dimer Mott insulator

TL;DR

This study reveals electron correlation-induced relaxor ferroelectricity in a molecular dimer Mott insulator, highlighting charge disproportionation and its coupling with magnetic interactions, distinct from spin liquid behavior.

Contribution

It demonstrates the emergence of relaxor ferroelectricity driven by electron correlations in a dimer Mott insulator, linking charge disproportionation to magnetic interactions.

Findings

Dielectric constant shows Curie-Weiss behavior with frequency dependence.

Anisotropic ferroelectricity indicates charge disproportionation.

Charge freezing temperature correlates with antiferromagnetic interactions.

Abstract

We have investigated the dielectric response in an antiferromagnetic dimer-Mott insulator beta'-(BEDT-TTF)2ICl2 with square lattice, compared to a spin liquid candidate kappa-(BEDT-TTF)2Cu2(CN)3. Temperature dependence of the dielectric constant shows a peak structure obeying Curie-Weiss law with strong frequency dependence. We found an anisotropic ferroelectricity by pyrocurrent measurements, which suggests the charge disproportionation in a dimer. The ferroelectric actual charge freezing temperature is related to the antiferromagnetic interaction, which is expected to the charge-spin coupled degrees of freedom in the system.