Organic conductors—from fundamentals to nonlinear conductivity

Organic conductors are studied from the viewpoint of the high conductivity in organic metals and superconductors, as well as from the application oriented viewpoint of organic electronics. This review provides a brief survey of organic charge-transfer salts, with particular emphasis on their electronic structure and energy band calculations, together with an elementary introduction to strong-electron-correlation physics. In particular, incommensurate organic superconductors based on MDT-TSF (methylenedithiotetraselenafulvalene) family donors are reviewed. Finally, the recently rising interest in nonlinear conductivity is described, including a historical survey of various works of nonlinear conductivity, as well as the nonlinearity arising from the competing charge order in the so-called θ-phase materials.