Purely electronic THz polarization in dimer Mott insulators

TL;DR

This paper predicts purely electronic polarization modes in the THz range for dimer Mott insulators, arising from intradimer dipole oscillations coupled with interdimer bond order oscillations, influencing their dielectric properties.

Contribution

It introduces the concept of purely electronic THz polarization modes in dimer Mott insulators and explores their origin and impact on dielectric behavior.

Findings

Low-frequency collective modes from intradimer dipole and interdimer bond oscillations.

Ferroelectric ground state near the Mott transition boundary due to electron-lattice coupling.

Significant role of collective motions in dielectric properties of the material.

Abstract

We theoretically discover purely electronic polarization modes in THz frequency region in dimer Mott insulators $\kappa$-(BEDT-TTF)$_2$X. The unusual low-frequency modes arise from the coupling between the oscillation of intradimer electric dipole moments and that of alternating interdimer bond orders. These collective motions play an important role in the dynamical dielectric properties of the dimer Mott insulators. Near the phase boundary of the dimer Mott transition, the ferroelectric ground state is realized by introducing electron-lattice coupling.