Emergent Collective Modes and Kinks in Electronic Dispersions

TL;DR

This paper demonstrates that kinks in electronic dispersions of strongly correlated systems originate from emergent internal collective modes, specifically spin fluctuations, rather than external mode coupling.

Contribution

It provides evidence that internal collective modes are responsible for dispersion kinks, advancing understanding of strongly correlated fermionic systems.

Findings

Kinks in fermionic dispersions are linked to internal collective modes.

Spin fluctuations are identified as the origin of these modes.

Emergent modes produce features similar to external mode coupling effects.

Abstract

Recently, it was shown that strongly correlated metallic fermionic systems [Nature Phys. 3, 168 (2007)] generically display kinks in the dispersion of single fermions without the coupling to collective modes. Here we provide compelling evidence that the physical origin of these kinks are emerging internal collective modes of the fermionic systems. In the Hubbard model under study these modes are identified to be spin fluctuations which are the precursors of the spin excitations in the insulating phase. In spite of their damping the emergent modes give rise to signatures very similar to features of models including coupling to external modes.