标题： 基于半经典非平衡格林函数方法的电子-声子耦合系统中的电子输运研究 显示英文标题

标题： A semiclassical nonequilibrium Green's Function approach to electron transport in systems exhibiting electron-phonon couplings

摘要： 我们为开放量子系统中的电子输运建立了一个半经典理论，该理论适用于当系统的声子动力学与电子输运时间尺度相当的情况。 从Keldysh非平衡格林函数形式出发，我们得到了包括由于声子动力学贡献的传播和小于电子格林函数的动力学方程，这些贡献是电子-声子耦合强度的二阶项。 所得方程假设系统的声子遵循经典的局部时间动力学，并具有delta相关噪声。 我们将该方法应用于研究周期性驱动量子点的充电/放电过程，以及单电子泵的三能级模型，分析了声子动力学在瞬态电流、电子占据和过程性能中的特征。 对于这些系统，我们采用涨落-耗散定理，并考虑外部谐波驱动的声子，其频率与电子调制频率相当，同时考虑不同的情况，包括电子-声子耦合强度的变化、对系统电子部分的耦合，以及同相和反相驱动。 我们的结果表明，该方法提供了一种有效的协议来描述超快瞬态现象中的核运动效应。 显示英文摘要

摘要： We formulate a semiclassical theory for electron transport in open quantum systems with electron-phonon interactions adequate for situations when the system's phonon dynamics is comparable with the electron transport timescale. Starting from the Keldysh non-equilibrium Green's function formalism we obtain equations of motion for the retarded and lesser electronic Green's functions including contributions due to the phonon dynamics up to second order in the electron-phonon coupling strength. The resulting equations assume that the system's phonon follow classical time-local dynamics with delta-correlated noise. We apply our method to the study of the charging/discharging of a periodically driven quantum dot, and a three-level model for a single-electron pump, analyzing the signatures in the transient current, electron population and process performance of the phonon dynamics. For these systems, we adopt the fluctuation-dissipation theorem and consider external harmonic driving of the phonon at frequencies comparable with the electron modulation, and different scenarios, varying electron-phonon coupling strength, coupling to the electron part of the system, and in phase and anti-phase driving. Our results illustrate that our method provides an efficient protocol to describe the effects of nuclear motion in ultrafast transient phenomena.