The strongly nonlinear current-voltage $\left(I\text{−}V\right)$ characteristics and the large negative magnetoresistance (MR) are observed at low temperatures in the one-dimensional organic conductor $\text{TPP}{\left[\text{Fe}\left(\text{Pc}\right){\left(\text{CN}\right)}_2\right]}_2$. The nonlinear $I\text{−}V$ curves are interpreted as the transport of the electrons and holes excited from the charge ordered state on the $\text{Fe}\left(\text{Pc}\right){\left(\text{CN}\right)}_2$ chains, whose energy gap strongly depends on electric fields. The negative MR is enhanced as temperature decreases, and the resistance steeply changes over four orders of magnitude around 15 T at 1.5 K. This decrease is associated with a magnetic torque anomaly, and the energy gap is rapidly reduced around 15 T. The detailed analyses of the $I\text{−}V$ curves show that the electric flux distribution, i.e., the dimensionality of the Coulomb interaction between the carriers, also changes around 15 T.

• Received 16 October 2008

DOI:https://doi.org/10.1103/PhysRevB.80.085110