Magnetic origin of high-energy kink structure in heavily electron-doped Li$_{1+x}$FeAs

TL;DR

This study reveals that a high-energy kink in heavily electron-doped Li$_{1+x}$FeAs originates from magnetic interactions, with strong electron correlations especially in the $d_{xy}$ orbital, as shown by three-dimensional ARPES measurements.

Contribution

It provides the first detailed analysis linking high-energy kink structures to magnetic interactions in heavily electron-doped Li$_{1+x}$FeAs.

Findings

Strong renormalization of the $d_{xy}$ orbital indicating enhanced electron correlation.

Identification of two types of kink structures on the $d_{yz}$ band.

High-energy kink energy matches spin excitation energy, suggesting magnetic origin.

Abstract

We report the origin of a high-energy kink structure of heavily electron-doped nonsuperconducting Li$_{1+x}$FeAs observed by three-dimensional angle-resolved photoemission spectroscopy. The $d_{xy}$ orbital at the center of the Brillouin zone is strongly renormalized, indicating stronger electron correlation, exceeding that of stoichiometric LiFeAs despite the fact that the orbital characters of all bands remain unchanged. Two types of kink structure on the $d_{yz}$ band were identified: an isotropic kink at the binding energy of 20 meV, and another kink located at 100 meV observed only in the (110) direction. The higher-energy kink is considered to originate from a magnetic interaction, because the peak energy is consistent with that of a spin excitation.