Large Dielectric Constant and Giant Nonlinear Conduction in the Organic Conductor θ-(BEDT-TTF)2CsZn(SCN)4

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.Comment: 8 pages, 6 figures, in RevTeX format, submitted to J. Phys. Soc. Jp