Self-consistent Dual Boson approach to single-particle and collective excitations in correlated systems

TL;DR

This paper introduces a self-consistent dual boson method extending DMFT to accurately describe collective excitations and spectral renormalizations in correlated electron systems.

Contribution

The paper presents a novel dual boson scheme that is fully self-consistent on both single- and two-particle levels, capturing collective modes and spectral effects simultaneously.

Findings

Method is based on an effective impurity model with fermionic and bosonic hybridization.

Uses a dual Luttinger-Ward functional ensuring conservation laws.

Demonstrates accurate description of collective excitations in correlated systems.

Abstract

We propose an efficient dual boson scheme, which extends the DMFT paradigm to collective excitations in correlated systems. The theory is fully self-consistent both on the one- and on the two-particle level, thus describing the formation of collective modes as well as the renormalization of electronic and bosonic spectra on equal footing. The method employs an effective impurity model comprising both fermionic and bosonic hybridization functions. Only single- and two-electron Green's functions of the reference problem enter the theory, due to the optimal choice of the self-consistency condition for the effective bosonic bath. We show that the theory is naturally described by a dual Luttinger-Ward functional and obeys the relevant conservation laws.