Transport through an Anderson impurity: Current ringing, nonlinear magnetization, and a direct comparison of continuous-time quantum Monte Carlo and hierarchical quantum master equations
Transport through an Anderson impurity: Current ringing, nonlinear magnetization, and a direct comparison of continuous-time quantum Monte Carlo and hierarchical quantum master equations
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DOI：
10.1103/physrevb.92.085430
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发表时间：
2015-05
影响因子：
3.7
通讯作者：
R. Härtle;Guy Cohen;D. Reichman;A. Millis
中科院分区：
文献类型：
--
作者：
R. Härtle;Guy Cohen;D. Reichman;A. Millis
我们给出了一个详细的比较的层次量子主方程（HQME）方法的连续时间量子蒙特卡罗（CT-QMC）的方法，评估这些数值精确的计划在实际的非平衡计算杂质求解器的可用性。我们回顾的方法的主要特点，并讨论了相关的数值工作的缩放。我们证实了我们的讨论与明确的数值结果的非平衡输运性质的一个单一的网站安德森杂质。HQME方案的数值努力与模拟时间成线性比例，但随着温度的降低而增加（最坏的指数）。相比之下，CT-QMC在短时间内受温度的限制较少，但通常情况下，更长时间的成本也是指数级的。在建立了HQME方案的数值精确性之后，我们用它来阐明不同的方式来诱导通过杂质的初始动力学的传输的影响，讨论相干电流振荡的现象，称为电流振铃，并解释作为竞争加宽效应的结果的稳态磁化的非单调温度依赖性。我们还阐明了显着的非线性磁化动力学，它出现在中间的时间尺度上的存在下，一个不对称的耦合到电极。
We give a detailed comparison of the hierarchical quantum master equation (HQME) method to a continuous-time quantum Monte Carlo (CT-QMC) approach, assessing the usability of these numerically exact schemes as impurity solvers in practical nonequilibrium calculations. We review the main characteristics of the methods and discuss the scaling of the associated numerical effort. We substantiate our discussion with explicit numerical results for the nonequilibrium transport properties of a single-site Anderson impurity. The numerical effort of the HQME scheme scales linearly with the simulation time but increases (at worst exponentially) with decreasing temperature. In contrast, CT-QMC is less restricted by temperature at short times, but in general the cost of going to longer times is also exponential. After establishing the numerical exactness of the HQME scheme, we use it to elucidate the influence of different ways to induce transport through the impurity on the initial dynamics, discuss the phenomenon of coherent current oscillations, known as current ringing, and explain the non-monotonic temperature dependence of the steady-state magnetization as a result of competing broadening effects. We also elucidate the pronounced non-linear magnetization dynamics, which appears on intermediate time scales in the presence of an asymmetric coupling to the electrodes.