A new route towards the dynamical mean field theory of strongly correlated nonequilibrium systems based on hierarchical master equation methods

动态平均场理论是描述强相关物质的最成功的方法之一。这一成功很大程度上是基于对平衡性质的描述，但如果这些材料被逐出平衡态，人们对它们的了解就会少得多。问题是对集体现象的描述，这通常需要对潜在的多体问题进行精确的处理。到目前为止，特别是在非平衡情况下，这只能通过有限的方法来实现。因此，提出了发展和应用层次量子主方程技术来解决动力学平均场分析中的杂质问题。由此产生的方法有望克服以前方法的一些主要限制。例如，这包括对任何类型的（局部）相互作用、多轨道效应和可以模拟的时间尺度的描述。后者对于强相关系统尤其重要，因为相应的非平衡动力学可以跨越几个数量级。因此，例如，可以研究不可能存在于平衡状态中的状态或相。这种状态目前在许多实验中都有涉及，因为它们可能非常有趣，特别是对于许多技术应用。

Dynamical mean field theory is one of the most successful approaches to describe strongly correlated materials. This success is largely based on the description of equilibrium properties, but much less is known about these materials if they are driven away from equilibrium. The problem is the description of collective phenomena, which often require an exact treatment of the underlying many-body problem. To date and in particular for nonequilibrium situations, this can be achieved only by a limited number of approaches. It is therefore proposed to develop and employ hierarchical quantum master equation techniques to solve the impurity problem of the dynamical mean-field ansatz. The resulting methodology can be expected to overcome some of the major limitations of previous approaches. This includes, for example, the description of any type of (local) interactions, multiorbital effects and the time scales that can be simulated. The latter is particularly important for strongly correlated systems because the corresponding nonequilibrium dynamics can span several orders of magnitude. Thus, for example, states or phases may be studied that cannot exist in equilibrium situations. Such states are currently accessed in a number of experiments, because they may be very interesting, inter alia, for a number of technological applications.