Strong spin dependence of correlation effects in Ni due to Stoner excitations

TL;DR

This study reveals significant spin-dependent electron correlation effects in nickel, showing how Stoner excitations influence quasiparticle properties and providing quantitative insights into spin-dependent interactions.

Contribution

It provides the first experimental quantification of spin-dependent correlation effects and the effective Coulomb interaction in Ni due to Stoner excitations.

Findings

Strong spin-dependent renormalization observed in Ni(111)

Spin-dependent lifetime broadening differs between majority and minority $d$ states

Negligible spin dependence for $sp$ states

Abstract

Using high-resolution angle-resolved photoemission, we observe a strong spin-dependent renormalization and lifetime broadening of the quasiparticle excitations in the electronic band structure of Ni(111) in an energy window of $\sim$0.3 eV below the Fermi level. We derive a quantitative result for the spin-dependent lifetime broadening by comparing the scattering rates of majority and minority $d$ states, and further show that spin-dependent electron correlations are instead negligible for $sp$ states. From our analysis we experimentally determine the effective on-site Coulomb interaction $U$ caused by Stoner-like interband transitions between majority and minority $d$ states. The present results unambiguously demonstrate the remarkable impact of spin-dependent electron correlation effects originating from single-particle excitations in a prototypical 3$d$ transition metal, paving the way for further refinement of current many-body theoretical approaches.