Conservation in two-particle self-consistent extensions of dynamical mean-field theory
Conservation in two-particle self-consistent extensions of dynamical mean-field theory
复制标题
动态平均场理论的双粒子自洽扩展中的守恒
DOI：
10.1103/physrevb.96.075155
复制
发表时间：
2017
影响因子：
3.7
通讯作者：
Alexander I. Lichtenstein
中科院分区：
文献类型：
--
作者：
Friedrich Krien;Erik G. C. P. van Loon;Hartmut Hafermann;Junya Otsuki;Mikhail I. Katsnelson;Alexander I. Lichtenstein
动力学平均场理论（DMFT）的扩展使用量子杂质模型作为非微扰和精确可解的参考系，这对于处理强电子关联是必不可少的。通过引入杂质上的延迟相互作用，这些近似可以使两粒子自洽。这对哈伯德模型很有意义，因为它允许根据Mermin-Wagner定理在二维中抑制反铁磁相变，并包括玻色子涨落的影响。对于后者的物理上合理的描述，近似值应该是守恒的。在本文中，我们表明，两个粒子的自洽性和守恒的相互要求导致的基本问题。对于一个近似，这是两个粒子的自洽的电荷和纵向自旋通道，双重占用的晶格和杂质不再是一致的，当计算从单粒子的属性。对于电荷和纵向以及横向自旋通道中的自洽性的情况，这些要求甚至是相互排斥的，因此不可能存在守恒近似。我们说明了这些发现的两粒子自洽和保守的DMFT近似。
Extensions of dynamical mean-field theory (DMFT) make use of quantum impurity models as nonperturbative and exactly solvable reference systems which are essential to treat the strong electronic correlations. Through the introduction of retarded interactions on the impurity, these approximations can be made two-particle self-consistent. This is of interest for the Hubbard model because it allows to suppress the antiferromagnetic phase transition in two dimensions in accordance with the Mermin-Wagner theorem, and to include the effects of bosonic fluctuations. For a physically sound description of the latter, the approximation should be conserving. In this paper, we show that the mutual requirements of two-particle self-consistency and conservation lead to fundamental problems. For an approximation that is two-particle self-consistent in the charge and longitudinal spin channels, the double occupancy of the lattice and the impurity is no longer consistent when computed from single-particle properties. For the case of self-consistency in the charge and longitudinal as well as transversal spin channels, these requirements are even mutually exclusive so that no conserving approximation can exist. We illustrate these findings for a two-particle self-consistent and conserving DMFT approximation.