Kinks in the electronic dispersion of the Hubbard model away from half filling

TL;DR

This study investigates the origin of kinks in the electronic dispersion of doped strongly correlated systems using DMFT, revealing their connection to spin fluctuations and energy scale separation near Mott transitions, with implications for cuprate superconductors.

Contribution

It extends the understanding of dispersion kinks from half-filled to doped systems, highlighting the role of spin fluctuations and energy scale separation, and compares multiple algorithms for analysis.

Findings

Kinks occur with strong spin fluctuations and energy scale separation.

Kink energies and doping dependence match cuprate observations.

DMFT captures key features despite neglecting spatial correlations.

Abstract

We study kinks in the electronic dispersion of a generic strongly correlated system by dynamic mean-field theory (DMFT). The focus is on doped systems away from particle-hole symmetry where valence fluctuations matter potentially. Three different algorithms are compared to asses their strengths and weaknesses, as well as to clearly distinguish physical features from algorithmic artifacts. Our findings extend a view previously established for half-filled systems where kinks reflect the coupling of the fermionic quasiparticles to emergent collective modes, which are identified here as spin fluctuations. Kinks are observed when strong spin fluctuations are present and, additionally, a separation of energy scales for spin and charge excitations exists. Both criteria are met by strongly correlated systems close to a Mott-insulator transition. The energies of the kinks and their doping dependence fit well to the kinks in the cuprates, which is surprising in view of the spatial correlations neglected by DMFT.