Electronic Ferroelectricity in a Dimer Mott Insulator

TL;DR

This paper investigates the coexistence and competition of magnetic and ferroelectric phases in a dimer-Mott insulator, revealing dielectric fluctuations near phase boundaries and implications for specific organic materials.

Contribution

It derives an effective Hamiltonian for a dimer-Mott insulator and analyzes charge and magnetic structures using mean-field and Monte Carlo methods, highlighting the exclusive nature of magnetic and ferroelectric phases.

Findings

Magnetic and ferroelectric phases are mutually exclusive.

Dielectric fluctuations are significant near phase boundaries.

Results have implications for the organic compound kappa-(BEDT-TTF)_2Cu_2(CN)_3.

Abstract

Motivated from recent experiments in kappa-(BEDT-TTF)_2Cu_2(CN)_3, dielectric and magnetic properties in a dimer-Mott insulator are studied. We derive the effective Hamiltonian where the number of electron per dimer is taken to be one. Charge and magnetic structures in finite temperature are obtained by using the mean-field and Monte-Carlo methods. Magnetic and ferroelectric phases are exclusive with each other. Dielectric fluctuation is remarkable near a phase boundary between dimer-Mott phase and ferroelectric phase. Implications of the present results for kappa-(BEDT-TTF)_2Cu_2(CN)_3 are discussed.