Search for quantum electronic dipoles in the dimerized \kappa-(BEDT-TTF)2Cu[N(CN)2]Cl salt

TL;DR

This study investigates the dielectric properties of ppa-(BEDT-TTF)2Cu[N(CN)2]Cl, concluding that its dielectric response is due to magnetic domain dynamics rather than quantum electric dipoles, challenging previous ferroelectricity claims.

Contribution

The paper provides evidence against the existence of quantum electric dipoles in the material, attributing dielectric behavior to magnetic domain phenomena instead.

Findings

Optical spectroscopy rules out charge imbalance and quantum electric dipoles.

Dielectric response attributed to magnetic domain wall relaxations.

No evidence supporting purely electronic ferroelectricity in the system.

Abstract

The Mott insulator \kappa-(BEDT-TTF)2Cu[N(CN)2]Cl consists of molecular dimers arranged on an anisotropic triangular lattice and develops a canted antiferromagnetic ground state. It has recently been suggested that this system features purely electronic ferroelectricity which requires an electric dipole moment. Optical spectroscopy clearly rules out charge imbalance in this system, which excludes the existence of quantum electric dipoles on the dimers and subsequently a dipolar spin coupling. We suggest that the prominent in-plane dielectric response in \kappa-(BEDT-TTF)2Cu[N(CN)2]Cl is due to short-range discommensurations of the antiferromagnetic phase in the temperature range 30 < T < 50 K, and domain wall relaxations at lower temperatures.