Short-time dynamics of correlated finite fermion systems - a Nonequilibrium Green functions approach

多体和少体系统的非平衡量子动力学一直是理论物理中悬而未决的问题之一。最近，由于在从超冷原子到凝聚态物质以及高密度等离子体和原子和分子系统的广泛领域中的新的应用和实验，这一主题获得了新的兴趣。实验进展使人们能够以时间分辨的方式获得新的观测数据，远远超过宏观系统的平均热力学数量，这对理论提出了相当大的挑战。对于远离平衡的相互作用的量子多体系统的精确建模是非常具有挑战性的，因为存在大量的独立变量，并且允许使用基态或平衡结果作为输入的微扰方法的崩溃。此外，同时存在控制非平衡动力学、关联的重要性和有限尺寸效应的多个时间尺度对于任何给定的高级方法的适用性都是具有挑战性的。激发的初始阶段、碰撞重分布和松弛的开始特别难以充分描述，这就需要先进的多体理论方法。然而，这些方法在计算上是昂贵的，因此，到目前为止，一直被限制在短时间尺度或/和小系统规模。本项目旨在利用非平衡格林函数领域最近的突破，显著放宽这些限制。除了理论方法的发展外，该项目还将在充分考虑电子关联的短激光脉冲下的石墨烯纳米带异质结构的短期动力学方面获得新的结果。

Nonequilibrium quantum dynamics of many-body and few-body systems remains one of the unresolved problems of theoretical physics. Recently this topic gained new interest due to novel applications and experiments in a broad range of fields ranging from ultracold atoms to condensed matter as well as to dense plasmas and atomic and molecular systems. Experimental progress giving time-resolved access to new observables well beyond average thermodynamic quantities of macroscopic systems poses a considerable challenge to theory. Accurate modeling of interacting quantum many-body systems far from equilibrium is very challenging due to the large number of independent variables and the breakdown of perturbative approaches that would allow to use ground state or equilibrium results as an input. Moreover, the simultaneous presence of multiple time scales governing nonequilibrium dynamics, the importance of correlations and finite size effects is challenging for the applicability of any given advanced method. The initial stage of excitation, collisional redistribution, and onset of relaxation is particularly difficult to describe adequately, requiring advanced methods of many-body theory. However, these methods are computationally expensive and, therefore, until now, have been restricted to short time scales or/and small system sizes. The present project aims to significantly relieve these restrictions, taking advantage of recent breakthroughs in the field of nonequilibrium Green functions. Aside from the development of theoretical methods the project will obtain new results for the short-time dynamics of graphene nanoribbon heterostructures exposed to short laser pulses that fully take into account electronic correlations.