超导纳米结中的猝灭动力学：亚稳态和动力学杨-李零点
Quench dynamics in superconducting nanojunctions: metastability and dynamical Yang-Lee zeros
摘要：
我们用全计数统计分析方法研究了相位或电压偏置超导纳米结形成后的电荷转移动力学。我们证明了生成函数的零点的演化允许人们以与平衡态统计力学中配分函数的杨-李零点的积累与相变有关的相同方式来识别不同的多体状态的种群。我们给出了一个精确的表达式连接的动力学零点的电荷转移累积量和讨论时，基于“主导”零点的近似是有效的。我们发现，对于一般的参数值，系统陷入一个亚稳态，其特征在于由许多体状态的非平衡人口，这是依赖于初始条件。我们特别研究的动态切换率的效果表明，与直觉相反，从热平衡的偏差增加较慢的速率。在电压偏置的情况下，达到稳定状态与初始条件无关。我们的方法使我们能够获得准确的结果，稳态电流和噪声的定量协议与稳态方法来描述多个Andreev反射制度。最后，我们讨论了突然电压下降后的系统动力学，通过适当选择初始电压来调节多体态种群的可能性，提供了一种可行的实验方法来访问淬火动力学和控制系统的状态。
英文摘要：
We study the charge transfer dynamics following the formation of a phase or voltage biased su- perconducting nano-junction using a full counting statistics analysis. We demonstrate that the evolution of the zeros of the generating function allows one to identify the population of different many body states much in the same way as the accumulation of Yang-Lee zeros of the partition function in equilibrium statistical mechanics is connected to phase transitions. We give an exact expression connecting the dynamical zeros to the charge transfer cumulants and discuss when an approximation based on "dominant" zeros is valid. We show that, for generic values of the parameters, the system gets trapped into a metastable state characterized by a non-equilibrium population of the many body states which is dependent on the initial conditions. We study in particular the effect of the switching rates in the dynamics showing that, in contrast to intuition, the deviation from thermal equilibrium increases for the slower rates. In the voltage biased case the steady state is reached independently of the initial conditions. Our method allows us to obtain accurate results for the steady state current and noise in quantitative agreement with steady state methods developed to describe the multiple Andreev reflections regime. Finally, we discuss the system dynamics after a sudden voltage drop showing the possibility of tuning the many body states population by an appropriate choice of the initial voltage, providing a feasible experimental way to access the quench dynamics and control the state of the system.
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