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首页> 外文期刊>Physical review >Comparison between scattering-states numerical renormalization group and the Kadanoff-Baym-Keldysh approach to quantum transport: Crossover from weak to strong correlations
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Comparison between scattering-states numerical renormalization group and the Kadanoff-Baym-Keldysh approach to quantum transport: Crossover from weak to strong correlations

机译：散射状态数值归一化组与Kadanoff-Baym-Keldysh量子传输方法之间的比较：从弱相关到强相关的交叉

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摘要

The quantum transport through nanoscale junctions is governed by the charging energy U of the device. We employ the recently developed scattering-states numerical renormalization-group approach to open quantum systems to study nonequilibrium Green's functions and current-voltage characteristics of such junctions for small and intermediate values of U. We establish the accuracy of the approach by a comparison with diagrammatic Kadanoff-Baym-Keldysh results which become exact in the weak-coupling limit U→0. We demonstrate the limits of the diagrammatic expansions at intermediate values of the charging energy. While the numerical renormalization-group approach correctly predicts only one single, universal low-energy scale at zero bias voltage, some diagrammatic expansions yield two different low-energy scales for the magnetic and the charge fluctuations. At large voltages, however, the self-consistent second Born as well as the GW approximation reproduce the scattering-states renormalization-group spectral functions for symmetric junctions while for asymmetric junctions the voltage-dependent redistribution of spectral weight differs significantly in the different approaches. The second-order perturbation theory does not capture the correct single-particle dynamics at large bias and violates current conservation for asymmetric junctions.
机译：通过纳米级结的量子传输受器件的充电能量U控制。我们采用最新开发的散射态数值重归一化组方法来研究开放量子系统，以研究U的中小值时此类结的非平衡格林函数和电流-电压特性。我们通过与图表的比较来确定该方法的准确性Kadanoff-Baym-Keldysh结果在弱耦合极限U→0中变得精确。我们在充电能量的中间值处演示了图解扩展的极限。尽管数值归一化组方法正确地预测了零偏置电压下的一个单一的通用低能标度，但一些图解展开式却产生了两种不同的磁能和电荷波动低能标度。但是，在大电压下，自洽的第二Born以及GW近似值再现了对称结的散射状态重归一化组光谱函数，而对于非对称结，光谱权重的电压相关重新分布在不同方法中有显着差异。二阶微扰理论不能在大偏差下捕获正确的单粒子动力学，并且违反了不对称结的电流守恒。

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