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TT: Fachverband Tiefe Temperaturen

TT 62: Correlated Electrons: Method Development 2

TT 62.3: Vortrag

Donnerstag, 19. März 2020, 15:30–15:45, HSZ 204

Consistent partial bosonization of the extended Hubbard model — •Viktor Harkov^1,2, Alexander I. Lichtenstein^1,2,3, and Evgeny A. Stepanov^1,3 — ¹Institute of Theoretical Physics, University of Hamburg, 20355 Hamburg, Germany — ²European X-Ray Free-Electron Laser Facility, 22869 Schenefeld, Germany — ³Theoretical Physics and Applied Mathematics Department, Ural Federal University, 620002 Ekaterinburg, Russia

A simple but efficient description of collective electronic excitations in realistic systems can be achieved performing a partial bosonization of collective fermionic fluctuations in leading channels of instability. In some approximations a simultaneous account for different bosonic channels gives rise to a famous Fierz ambiguity in decomposition of the local Coulomb interaction into considered channels, which drastically affects the final result of the method. We introduce a consistent partial bosonization of the fermionic problem that finally solves the famous Fierz ambiguity problem. We apply our method to extended Hubbard model and derive an effective theory that is formulated in terms of original fermionic degrees of freedom, new bosonic fields, and an effective fermion-boson interaction. We show that the fermion-fermion interaction can be safely excluded from the model, which results in a very simple approximation that significantly improves all existing partially bosonized theories. In addition, our approach allows an inclusion of magnetic fluctuations in the GW scheme in a consistent way.

[1] E. A. Stepanov, V. Harkov, and A. I. Lichtenstein, Phys.Rev. B 100, 205115 (2019).