Large dielectric constant and giant nonlinear conduction in the organic conductor theta-(BEDT-TTF)_2CsZn(SCN)_4

TL;DR

This study reveals that the organic conductor theta-(BEDT-TTF)_2CsZn(SCN)_4 exhibits a giant dielectric constant and nonlinear conduction behavior, indicating collective charge excitations despite lacking long-range order.

Contribution

It demonstrates the presence of collective charge excitations in theta-(BEDT-TTF)_2CsZn(SCN)_4 through dielectric and conductivity measurements, highlighting novel nonlinear conduction phenomena.

Findings

Large dielectric constant with relaxation behavior

Giant nonlinear conduction with hysteresis

Changes by 100-1000 times at threshold

Abstract

The dielectric constant and ac conductivity have been measured for the layered organic conductor theta-(BEDT-TTF)_2CsZn(SCN)_4 along the out-of-plane direction, which show a relaxation behavior similar to those in the charge-density-wave conductor. Most unexpectedly, they exhibit a large bias dependence with a hysteresis, and changes in magnitude by 100-1000 times at a threshold. These findings are very similar to the collective excitation of the charge density wave. theta-$(BEDT-TTF)_2CsZn(SCN)_4 has collective excitations associated with charge ordering, though it shows no clear indication of long range order.