1. Sum rule violation in self-consistent hybridization expansions.
- Author
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Rüegg, Andreas, Gull, Emanuel, Fiete, Gregory A., and Millis, Andrew J.
- Subjects
- *
SELF-consistent field theory , *SUM rules (Physics) , *METAL inclusions , *ORBITAL hybridization , *HIGH frequency transformers , *MONTE Carlo method - Abstract
We show that for multiorbital quantum impurity models the noncrossing approximation and one-crossing approximation versions of the self-consistent hybridization expansions violate the sum rules relating the coefficients of the high-frequency expansion of the self-energy and the product of the self-energy and Green's function to thermodynamic expectation values. Comparison of noncrossing/one-crossing results to numerically exact quantum Monte Carlo calculations shows that the consistency with sum rules provides a useful estimate of the reliability of the approximations. The sum rule violations are more pronounced, and therefore the quality of the noncrossing/one-crossing approximation is poorer, in situations with multiple orbitals and away from particle-hole symmetry but becomes less severe as the correlation strength increases. The one-crossing approximation is markedly superior to the noncrossing approximation. [ABSTRACT FROM AUTHOR]
- Published
- 2013
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