Full-counting statistics for molecular junctions: Fluctuation theorem and singularities
Full-counting statistics for molecular junctions: Fluctuation theorem and singularities
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DOI：
10.1103/physrevb.87.115407
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发表时间：
2012-10
影响因子：
3.7
通讯作者：
Y. Utsumi;O. Entin-Wohlman;A. Ueda;A. Aharony
中科院分区：
文献类型：
--
作者：
Y. Utsumi;O. Entin-Wohlman;A. Ueda;A. Aharony
本文研究了电荷通过弱耦合局域爱因斯坦声子的单能级量子点时的全计数统计。的累积量生成函数的解析表达式，精确到二阶的电子-声子耦合和有效的有限的电压和温度，在扩展的宽带限制。结果解释了由源漏偏压引起的非平衡声子分布，同时满足涨落定理。将计数场扩展到复平面，我们研究了累积量生成函数可能的奇异性的位置，并利用它们来识别电子转移受耦合到声子的不同影响的制度。在大偏差分析中，我们发现概率分布中的扭结，类似于热力学中的一阶相变，这将是电子-声子相关性的独特标志。这种扭结反映了这样一个事实：尽管一旦电压超过其频率，声子的非弹性散射可以将电子与偏置方向相反地散射，但根据波动定理，这永远不会在零温度下产生逆偏置流动的电流。DOI：10.1103/PhysRevB.87.115407
We study the full-counting statistics of charges transmitted through a single-level quantum dot weakly coupled to a local Einstein phonon which causes fluctuations in the dot energy. An analytic expression for the cumulant generating function, accurate up to second order in the electron-phonon coupling and valid for finite voltages and temperatures, is obtained in the extended wide-band limit. The result accounts for nonequilibrium phonon distributions induced by the source-drain bias voltage, and concomitantly satisfies the fluctuation theorem. Extending the counting field to the complex plane, we investigate the locations of possible singularities of the cumulant generating function, and exploit them to identify regimes in which the electron transfer is affected differently by the coupling to the phonons. Within a large-deviation analysis, we find a kink in the probability distribution, analogous to a first-order phase transition in thermodynamics, which would be a unique hallmark of the electron-phonon correlations. This kink reflects the fact that although inelastic scattering by the phonons once the voltage exceeds their frequency can scatter electrons opposite to the bias, this will never generate current flowing against the bias at zero temperature, in accordance with the fluctuation theorem. DOI: 10.1103/PhysRevB.87.115407