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An organic thyristor


Thyristors are a class of nonlinear electronic device that exhibit bistable resistance—that is, they can be switched between two different conductance states1. Thyristors are widely used as inverters (direct to alternating current converters) and for the smooth control of power in a variety of applications such as motors and refrigerators. Materials and structures that exhibit nonlinear resistance of this sort are not only useful for practical applications: they also provide systems for exploring fundamental aspects of solid-state and statistical physics. Here we report the discovery of a giant nonlinear resistance effect in the conducting organic salt2 θ-(BEDT-TTF)2CsCo(SCN)4, the voltage-current characteristics of which are essentially the same as those of a conventional thyristor. This intrinsic organic thyristor works as an inverter, generating an alternating current when a static direct-current voltage is applied. Whereas conventional thyristors consist of a series of diodes (their nonlinearity comes from interface effects at the p-n junctions), the present salt exhibits giant nonlinear resistance as a bulk phenomenon. We attribute the origin of this effect to the current-induced melting of insulating charge-order domains, an intrinsically non-equilibrium phenomenon in the sense that ordered domains are melted by a steady flow.

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Figure 1: Nonlinear resistance Vsample/Iex of a θ-(BEDT-TTF)2CsCo(SCN)4 crystal (sample B1) at 4.2 K.
Figure 2: Inverter (d.c.–a.c. conversion) phenomena in θ-(BEDT-TTF) 2 CsCo(SCN) 4 measured at 4.2 K.
Figure 3
Figure 4: Nonlinear resistance Vsample/Iex plotted as a function of 1/ T for various Iex.
Figure 5: Diffuse scattering intensities for θ -(BEDT-TTF) 2 CsZn(SCN) 4 with various external currents applied along the c -axis direction at 12 K.


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We thank K. Inagaki for collaboration, and A. Maeda for technical advice for nonlinear-conduction and noise measurements. We also thank S. Tasaki, S. Kurihara, M. Abdel-Jawad, and N. E. Hussey for discussions. This work was partially supported by MEXT, the Grant-in-Aid for Scientific Research, and by the 21st Century COE Program at Waseda University. Author Contributions F.S. did the electrical measurement, I.T. did the project planning and analysis, H.M. and T.M. did the sample preparation and chemical characterization, and M.W., N.I., Y.N. and Y.N. did the diffraction in electric fields.

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Correspondence to I. Terasaki.

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Sawano, F., Terasaki, I., Mori, H. et al. An organic thyristor. Nature 437, 522–524 (2005).

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