Nonlinear electronic transport in TTF-TCNQ observed by microwave harmonic mixing

The field dependent electronic conductivity of single crystals of TTF-TCNQ has been studied in both the metallic and the semiconducting range by means of microwave harmonic mixing, a method which excludes a contribution to the non-linearity by lattice heating. Because of the small strength of the applied field, the deviations from Ohm's law are also small such that they are proportional to the square of the field strength. The results in the semiconducting range are explained by the assumption of pinned charge density waves which are depinned by means of the microwave electric field.