Nonlinear conduction detected by the harmonic measurement in an organic molecular conductor α-(BEDT-TTF)₂I₃

We have investigated the nonlinear conduction of an organic molecular conductor α-(BEDT-TTF)₂I₃ in the charge order phase by measuring the harmonic component of the output voltage obtained when an alternating current is applied. Extrinsic components due to waveform distortion in the amplifier are usually included in the signal, which were carefully removed to attain high sensitivity to detect intrinsic nonlinearity. Thus, we have identified the intrinsic nonlinear conduction in low current region (~nA), in which non-ohmic response has not seen in the conventional I-V characteristic measuring method [1]. To explain our result, we suggest a model in terms of nonequilibrium hot charge carriers [2], in which the carrier mobility varied with electric field. [1] K. Kodama et al., J. Phys. Soc. Jpn 81, 114722 (2012). [2] T. Peterseim et al., PRB. 93, 245133 (2016).