论文标题
电荷有机盐的三阶电导率$α$ - （bedt-ttf）$ _ 2 $ i $ _3 $
Third-order Electrical Conductivity of the Charge-ordered Organic Salt $α$-(BEDT-TTF)$_2$I$_3$
论文作者
论文摘要
我们使用对非线性信号敏感的AC桥技术对有机导体$α$ - （BEDT-TTF）进行了三阶电导率测量。即使在低电场处，三阶电导$ g_3 $也可以清楚地观察到，有趣的是，$ g_3 $的增强量超过了电荷订单过渡温度$ t _ {\ rm co} = 136 $ 〜k。观察到的$ G_3 $的频率依赖性与渗透模型不相容，其中随机电阻网络中的焦耳加热与非线性传导有关。相反，我们根据具有较大介电常数的材料的现象学模型来争辩放松时间的非线性，并发现第三阶电导$ g_3 $对应于三阶电敏感性$χ_3$。由于非线性易感性被称为高阶多极订购的探针，因此在$ t _ {\ rm co} $上方对$ g_3 $的发散行为的当前观察结果揭示了有机系统的电荷级过渡时的基础四极不稳定。
We performed third-order electrical conductivity measurements on the organic conductor $α$-(BEDT-TTF)$_2$I$_3$ using an ac bridge technique sensitive to nonlinear signals. Third-order conductance $G_3$ is clearly observed even at low electric fields, and interestingly, $G_3$ is critically enhanced above the charge-order transition temperature $T_{\rm CO}=136$~K. The observed frequency dependence of $G_3$ is incompatible with a percolation model, in which a Joule heating in a random resistor network is relevant to the nonlinear conduction. We instead argue the nonlinearity of the relaxation time according to a phenomenological model on the mobility in materials with large dielectric constants, and find that the third-order conductance $G_3$ corresponds to the third-order electric susceptibility $χ_3$. Since the nonlinear susceptibility is known as a probe for higher-order multipole ordering, the present observation of the divergent behavior of $G_3$ above $T_{\rm CO}$ reveals an underlying quadrupole instability at the charge-order transition of the organic system.
