Kink far below the Fermi level reveals new electron-magnon scattering channel in Fe

TL;DR

This study reveals a new electron-magnon scattering channel in iron by combining advanced spectroscopy measurements with first-principles many-body calculations, showing a deep-energy kink in the electronic band structure.

Contribution

The paper introduces a novel first-principles method to identify a deep-energy kink caused by electron-magnon interactions in ferromagnetic materials.

Findings

Observation of a kink at 1.5 eV binding energy in Fe

Identification of a many-body state involving a photohole and spin-flip excitations

Enhanced understanding of electron-magnon interactions in spintronics

Abstract

Many properties of real materials can be modeled using ab initio methods within a single-particle picture. However, for an accurate theoretical treatment of excited states, it is necessary to describe electron-electron correlations including interactions with bosons: phonons, plasmons, or magnons. In this work, by comparing spin- and momentum-resolved photoemission spectroscopy measurements to many-body calculations carried out with a newly developed first-principles method, we show that a kink in the electronic band dispersion of a ferromagnetic material can occur at much deeper binding energies than expected (E_b=1.5 eV). We demonstrate that the observed spectral signature reflects the formation of a many-body state that includes a photohole bound to a coherent superposition of renormalized spin-flip excitations. The existence of such a many-body state sheds new light on the physics of the electron-magnon interaction which is essential in fields such as spintronics and Fe-based superconductivity.