Tunneling conduction in quasi-one-dimensional compound KFe(S_1-xSe_x)₂

The nonmetallic behavior in the resistivity of KFeS₂ is thought to be dominated by tunneling process between the metallic domains. Two theoretical models are examined: "activated tunneling" and "fluctuation induced tunneling" respectively developed by Abeles et al. and by Sheng. Both theories explain the temperature dependence of the resistivity in a wide temperature range. However, the dependence on the applied electric field is satisfactorily explained only by the latter model. Selenium substitution for sulfur sites brings effectively a reduction of height and width of the barrier potential at the domain boundary.