Conservation in two-particle self-consistent extensions of dynamical-mean-field-theory
| Autor: | Krien, F., van Loon, E. G. C. P., Hafermann, H., Otsuki, J., Katsnelson, M. I., Lichtenstein, A. I. |
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| Rok vydání: | 2017 |
| Předmět: | |
| Zdroj: | Phys. Rev. B 96, 075155 (2017) |
| Druh dokumentu: | Working Paper |
| DOI: | 10.1103/PhysRevB.96.075155 |
| Popis: | Extensions of dynamical-mean-field-theory (DMFT) make use of quantum impurity models as non-perturbative 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 channel, the double occupancy of the lattice and the impurity are 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. Comment: 17 pages, 9 figures |
| Databáze: | arXiv |
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