Large dielectric constant and giant nonlinear conduction in the organic conductor θ-(BEDT-TTF)2CsZn(SCN)4

The dielectric constant and ac conductivity have been measured for the layered organic conductor theta(BEDT-TTF)(2)CsZn(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)(2)CsZn(SCN)(4) has collective excitations associated with charge ordering, though it shows no clear indication of long range order.