Effect of cooling rate on charge ordering in θ-(BEDT-TTF)2RbZn(SCN)4

We present results of measurements of the conductance and dielectric permittivity at various cooling and heating rates through the phase transition into the charge-ordered state in theta-(BEDT-TTF)(2)RbZn(SCN)(4), [where BEDT-TTF is bis(ethylene-dithio)tetrathiafulvalene]. With increasing cooling rate, the sharpnesss of the first-order phase transition and the divergence of the dielectric permittivity associated with it are gradually suppressed. We explain the obtained results by the suggestion of combined contributions of electron and lattice subsystems to the formation of the charge-ordered state in two-dimensional organic compounds.