Collective Excitations in the Charge-Ordered Phase of alpha-(BEDT-TTF)2I3

TL;DR

This study investigates the charge response and collective excitations in the charge-ordered phase of alpha-(BEDT-TTF)2I3 using various spectroscopic techniques, revealing phason-like modes and domain-wall dynamics.

Contribution

It provides new insights into the collective excitations and dielectric modes in the charge-ordered state of alpha-(BEDT-TTF)2I3, highlighting the roles of phason-like excitations and domain-wall motions.

Findings

Detection of two dielectric modes in the charge-ordered phase.

Identification of a phason-like excitation related to 2kF bond-charge density wave.

Observation of domain-wall pair motion between symmetry-broken domains.

Abstract

The charge response of charge-ordered state in the organic conductor alpha-(BEDT-TTF)2I3 is characterized by dc resistivity, dielectric and optical spectroscopy in different crystallographic directions within the two-dimensional conduction layer. Two dielectric modes are detected. The large mode is related to the phason-like excitation of the 2kF bond-charge density wave which forms in the ab plane. The small dielectric mode is associated with the motion of domain-wall pairs along the a- and b-axes between two types of domains which are created due to inversion symmetry breaking.