We have measured and analyzed the resistivity and voltage-current characteristics of the charge-ordered organic salt θ-(BEDT-TTF) 2CsM(SCN) 4 (M = Zn, Co, and Co 0.7Zn 0.3). At 4.3 K, all the samples show giant nonlinear conduction, in which the c-axis resistivity markedly decreases with external current by a factor of 10 against a small electric field of 1 V/cm. The temperature dependence of the resistivity is well described by an activation law, the activation energy of which is evaluated to be 2 meV in the lowcurrent limit, and linearly decreases with external current. The activation energy and x-ray intensity near q 2 = (0, k, 1/2) are found to show the same dependence on current density. This coincidence strongly suggests that the energy gap of the charge order indexed by q 2 is an order parameter of this phenomenon.
- Charge ordering
- Nonlinear conduction x-ray diffraction
- Organic conductor
ASJC Scopus subject areas
- Physics and Astronomy(all)