Dual Bethe-Salpeter equation for the multi-orbital lattice susceptibility within dynamical mean-field theory

Abstract

Dynamical mean-field theory describes the impact of strong local correlation effects in many-electron systems. While the single-particle spectral function is directly obtained within the formalism, two-particle susceptibilities can also be obtained by solving the Bethe-Salpeter equation. The solution requires handling infinite matrices in Matsubara frequency space. This is commonly treated using a finite frequency cut-off, resulting in slow linear convergence. A decomposition of the two-particle response in local and non-local contributions enables a reformulation of the Bethe-Salpeter equation inspired by the dual boson formalism. The re-formulation has a drastically improved cubic convergence with respect to the frequency cut-off, facilitating the calculation of susceptibilities in multi-orbital systems considerably. This improved convergence arises from the fact that local contributions can be measured in the impurity solver. The dual Bethe-Salpeter equation uses the fully reducible vertex which is free from vertex divergences. We benchmark the approach on several systems including the spin susceptibility of strontium ruthenate Sr${}_2$RuO${}_4$, a strongly correlated Hund's metal with three active orbitals.

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Cited by in corpus (5)

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• The finite-difference parquet method: Enhanced electron-paramagnon scattering opens a pseudogap
• Exchange interactions in itinerant magnets: the effects of local particle-hole irreducible vertex corrections and SU(2) symmetry of Hund interaction
• Non-perturbative effects of short-range spatial correlations at the two-particle level