Theory of nonlinear conduction for charge-ordered states in quasi-two-dimensional organic conductors

Nonlinear conduction in quasi-two-dimensional organic conductors θ -(BEDT-TTF) ₂X [BEDT-TTF=bis(ethylenedithio)tetrathiafulvalene] is investigated theoretically. By using a nonequilibrium Green's function method, an extended Peierls-Hubbard model attached to metallic electrodes is studied within the mean-field approximation. We show that in a coexistent state of stripe-type and nonstripe 3-fold charge orders, the former charge order is completely suppressed by the applied bias, whereas the latter charge order survives. This leads to selective melting of charge order of different origins. The disappearance of the stripe-type charge order largely alters the conduction behavior, which is consistent with the experimental findings.