Nonlinear dynamics of conduction electrons in organic conductors

Nonlinear conductivity of organic conductors is explained quantitatively starting from a phenomenological energy-balance equation. Experimental results of (TMET-TTP)₄PF₆ are presented, where TMET-TTP is 2-[4, 5-bis(methylthio)-1,3-dithiol-2-ylidene]-5-[4,5-ethylenedithio-1,3-dithiol-2-ylidene]-1,3,4,6-tetrathiapentalene, and the simulation reproduces the nonlinear properties very well, including the voltage-current characteristics, power-law excess conductivity, and temperature dependence of the threshold field and current. The obtained heat capacity is much smaller than the lattice heat capacity, indicating unimportance of the Joule heating. Since the organic conductors show very little hysteretic switching, the time dependence of the energy balance is traced explicitly, defining nonlinear dynamics of hypothetical electron temperature, which reproduces oscillating states similar to that of the organic thyristor and even chaotic states under certain circumstances. It is expected that transient phenomena such as oscillatory and random outputs in some sort of organic and inorganic nonlinear conductors are quantitatively explained by this method, which in turn affords a playground of nonlinear dynamics.