Abstract

We introduce a general scheme to consistently truncate equations of motion for Green’s functions. Our scheme is guaranteed to generate physical Green’s functions with real excitation energies and positive spectral weights. There are free parameters in our scheme akin to mean field parameters that may be determined to get as good an approximation to the physics as possible. As a test case we apply our scheme to a two-pole approximation for the 2D Hubbard model. At half-filling we find an insulating solution with several interesting properties: it has low expectation value of the energy and it gives upper and lower Hubbard bands with the full non-interacting bandwidth in the large U limit. Away from half-filling, in particular in the intermediate interaction regime, our scheme allows for several different phases with different number of Fermi surfaces and topologies.

Graphic abstract

中文翻译：

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基于部分正交化的运动截断方案方程

摘要

我们介绍了一种通用方案，用于一致地截断格林函数的运动方程。我们的方案可以保证产生具有实际激发能和正谱权重的物理格林函数。我们的方案中有一些自由参数，类似于平均场参数，这些参数可以确定为尽可能接近物理。作为测试案例，我们将我们的方案应用于2D Hubbard模型的两极近似。在半填充时，我们发现了一种绝缘解决方案，它具有几个有趣的属性：它具有较低的能量期望值，并且在大U中提供了具有完整非交互带宽的上，下Hu​​bbard频带。限制。除了半填充，特别是在中间交互方式中，我们的方案允许具有不同数量的费米面和拓扑的几个不同阶段。

图形摘要