Nonequilibrium charge ordering in θ-(BEDT-TTF)2MM′(SCN)4(M=Rb, Cs; M′=Co, Zn)

Giant nonlinear conduction in the charge ordered organic conductor θ‐(BEDT‐TTF)2MM′(SCN)4θ‐(BEDT‐TTF)2MM′(SCN)4 (M=CsM=Cs, Rb; M′=CoM′=Co, Zn) is analyzed in relation to the current-induced suppression of the charge ordered state characterized by a wave vector of q2=(0k12). On the basis of a theory of the nonequilibrium Peierls transition, the energy gap is calculated as a function of current density JextJext, which is found to depend weakly on temperature in an intermediate temperature range. This justifies the evaluation of the charge-order energy gap ΔΔ from the nonlinear resistivity ρρ assuming ρ∝exp[Δ(Jext)/kBT]ρ∝exp[Δ(Jext)/kBT], and Δ(Jext)Δ(Jext) is found to be consistent with the calculation. We compare the present results with nonequilibrium superconducting states induced by excess quasiparticles, and discuss a mechanism of current-induced suppression of the charge ordering in the title compound.