Energy transfer in the nonequilibrium spin-boson model: From weak to strong coupling.
Energy transfer in the nonequilibrium spin-boson model: From weak to strong coupling.
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DOI：
10.1103/physreve.96.012135
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发表时间：
2016-09
期刊：
影响因子：
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通讯作者：
Junjie Liu;Hui Xu;Baowen Li;Changqin Wu
中科院分区：
文献类型：
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作者：
Junjie Liu;Hui Xu;Baowen Li;Changqin Wu
为了研究非平衡自旋玻色子模型（NESB）中从弱到强系统-浴耦合区的能量转移，我们提出了极化子变换的非平衡绿色函数（NEGF）方法。通过结合极化子变换，我们能够处理系统浴耦合非微扰，从而在直接对比传统使用的NEGF方法，采取系统浴耦合作为一个扰动。马约拉纳费米子表示进一步利用戴森系列中的评估条款。这种方法不仅使我们能够处理弱以及强耦合制度，但也使调查的作用，偏置的能量转移。作为该方法的一个应用，我们研究了欧姆NESB。对于一个无偏自旋系统，我们的能量流的结果顺利桥梁预测的两个基准，即量子主方程和非平衡非相互作用blip近似，一个相当大的改进现有的理论。在偏置自旋系统中，我们发现在中间耦合区，由于能量转移的共振性质，能量电导存在偏置诱导的非单调行为。这一发现可能为纳米尺度上的能量传递提供了一个重要的量子控制旋钮。
To explore energy transfer in the nonequilibrium spin-boson model (NESB) from weak to strong system-bath coupling regimes, we propose a polaron-transformed nonequilibrium Green's function (NEGF) method. By combining the polaron transformation, we are able to treat the system-bath coupling nonperturbatively, thus in direct contrast to conventionally used NEGF methods which take the system-bath coupling as a perturbation. The Majorana-fermion representation is further utilized to evaluate terms in the Dyson series. This method not only allows us to deal with weak as well as strong coupling regimes but also enables an investigation on the role of bias in the energy transfer. As an application of the method, we study an Ohmic NESB. For an unbiased spin system, our energy current result smoothly bridges predictions of two benchmarks, namely, the quantum master equation and the nonequilibrium noninteracting blip approximation, a considerable improvement over existing theories. In case of a biased spin system, we found a bias-induced nonmonotonic behavior of the energy conductance in the intermediate coupling regime, resulting from the resonant character of the energy transfer. This finding may offer a nontrivial quantum control knob over energy transfer at the nanoscale.