论文标题
通过非线性运输研究
Insulating Phase in Two-dimensional Josephson-Junction Arrays Investigated by Nonlinear Transport
论文作者
论文摘要
我们通过系统地改变Josephson Energy $ e_ \ Mathrm {J} $的比率，并充电Energy $ e_ \ e_ \ m athrm {c} $，通过系统地改变约瑟夫森 - 结阵列（JJAS）的绝缘阶段的运输特性研究。观察到的电阻的温度依赖性表明JJAS不会显示出急剧的相变，而是表现出逐渐交叉到绝缘阶段。在低温下，如$ i = cv+bv^a $（$ a $，$ b $，$ b $和$ c $是温度依赖的系数），电流电压（$ i $ - $ v $）的特性变为非线性。通过考虑到库珀对之间对数相互作用的有限范围截止的影响，可以从berezinskii-kosterlitz-thouless机制来理解这种非线性行为。从非线性的分析中，我们将交叉温度推导为绝缘阶段，并确定绝缘侧的相图作为$ e_ \ mathrm {j} /e_ \ mathrm {c} $的函数。我们还表明，在非常低的温度下，$ i $ - $ v $特征不断发展为由一致的单孔对隧道引起的负差分电导。
We present experimental investigations of transport properties in the insulating phase of two-dimensional Josephson-junction arrays (JJAs) by systematically changing the ratio of Josephson energy $E_\mathrm{J}$ and charging energy $E_\mathrm{C}$. The observed temperature dependence of resistance indicates that the JJAs do not show a sharp phase transition but exhibit a gradual crossover to the insulating phase. At low temperatures, the current-voltage ($I$-$V$) characteristics become nonlinear as described by $I=cV+bV^a$ ($a$, $b$, and $c$ are temperature dependent coefficients). This nonlinear behavior is understood in terms of the Berezinskii-Kosterlitz-Thouless (BKT) mechanism by taking into account the influence of a finite-range cutoff of the logarithmic interaction between Cooper pairs. From the analysis of the nonlinearity, we deduce the crossover temperature to the insulating phase and determine the phase diagram in the insulating side as a function of $E_\mathrm{J} /E_\mathrm{C}$. We also show that, at very low temperatures, the $I$-$V$ characteristics continuously develop into the negative differential conductance caused by coherent single-Cooper-pair tunneling.
