Nonlinear electrical transport in (formula presented)

We study the current-voltage (formula presented) characteristics in a quasi-two-dimensional, (formula presented) coupled organic conductor (formula presented) which undergoes a metal-to-insulator transition associated with an antiferromagnetic ordering at (formula presented) Drastic nonlinear transport phenomena are observed in the (formula presented) curve, revealing a so-called negative resistance effect at an applied electric field or a current density higher than threshold (formula presented) or (formula presented) The overall (formula presented) curves are quite well explained phenomenologically by a nonlinear equation for a positive feedback system that the nonlinear conductivity proportional to (formula presented) with (formula presented) This indicates that some carrier decondensation mechanism works in the present antiferromagnetic insulator. Discussions are presented by following quite similar nonlinear phenomena observed in a variety of quasi-one-dimensional, mixed-stack, and segregated-stack, organic insulators.