基于部分正交化的运动方程截断格式
Equation of motion truncation scheme based on partial orthogonalization
摘要：
我们介绍了一个通用的计划，一贯截断运动方程的格林函数。我们的计划是保证产生物理格林函数与实激发能和积极的光谱权重。在我们的方案中有类似于平均场参数的自由参数，可以确定这些参数以获得尽可能好的物理近似。作为一个测试情况下，我们将我们的计划的两个极点近似的二维哈伯德模型。在半填充，我们发现一个绝缘的解决方案，具有几个有趣的属性：它具有较低的期望值的能量，它给出了上，下哈伯德带与充分的非相互作用的带宽在大U限制。远离半填充，特别是在中间相互作用制度，我们的计划允许几个不同的阶段，不同数量的费米表面和拓扑结构。
英文摘要：
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.
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