通用量子猝灭下多通道Kondo系统的预热化与瞬态动力学：来自大N Schwinger-Keldysh方法的洞察
Prethermalization and transient dynamics of the Multi-Channel Kondo systems under generic quantum quenches: Insights form Large-$N$ Schwinger-Keldysh approach
AI总结：
基于大N Schwinger-Keldysh方法，研究多通道Kondo杂质模型在量子猝灭后的瞬态动力学与预热化，揭示了纠缠态量子复苏、退相干机制及杂质自旋与复合玻色子间的非零有效温差，为非平衡多体量子系统的普适动力学提供了新视角。
摘要：
理解非平衡多体量子系统在当代物理学中至关重要。然而，尽管有先进的数值方法，捕捉此类系统的普适动力学仍具挑战。我们研究了多通道Kondo杂质（MCKI）模型，该模型包含具有非费米液体特性的过屏蔽Kondo态。利用大N Schwinger-Keldysh方法，我们研究了Kondo耦合突然改变后的瞬态动力学和长时间准平衡性质。我们考虑了两种初始态：过屏蔽Kondo态和高温费米液体态。在过屏蔽Kondo态中，我们观察到自旋-自旋关联和Kondo序参量的振荡，代表了纠缠态的量子复苏。在高温费米液体态中，振荡的缺失归因于退相干机制。系统达到准平衡，表现为杂质与传导电子间的非相干热化。我们观察到杂质自旋（Abrikosov费米子）与在杂质位形成的复合玻色子间存在非零有效温差。此准平衡即预热化，而完全热化在O(N)时间尺度上伴随1/N修正发生。我们讨论了量子冷却效应和量子玻尔兹曼方程。本研究为研究量子多体系统的大N量子场论处理奠定了基础，揭示了普适性质及预热化的新视角。
英文摘要：
Understanding out-of-equilibrium many-body quantum systems is crucial in contemporary physics. However, capturing the universal dynamics of such systems remains challenging despite advanced numerical methods. We investigate the multi-channel Kondo impurity (MCKI) model, hosting an over-screened Kondo state with non-Fermi liquid characteristics. Using the large-N Schwinger-Keldysh approach, we study transient dynamics and long-time quasi-equilibrium properties following a sudden change in the Kondo coupling. We consider two initial states: over-screened Kondo and high-temperature Fermi liquid. In the over-screened Kondo state, we observe oscillations in spin-spin correlations and the Kondo order parameter, representing quantum revival of the entangled state. In the high-temperature Fermi liquid state, the absence of oscillations is attributed to the de-phasing mechanism. The system reaches quasi-equilibrium, manifested as incoherent thermalization between the impurity and conduction electrons. We observe a non-vanishing effective temperature difference between the impurity spin (Abrikosov fermion) and the composite boson formed with conduction electrons at the impurity site. This quasi-equilibrium is prethermalization, while complete thermalization occurs on an O(N) timescale with 1/N correction. We discuss the quantum cooling effect and quantum Boltzmann equations. Our study establishes a foundation for investigating large-N quantum field theory treatment of quantum many-body systems, revealing universal properties and a fresh perspective on prethermalization.
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