Fingerprints of entangled spin and orbital physics in itinerant ferromagnets via angle resolved $resonant$ photoemission

TL;DR

This paper introduces a new ab-initio method using angle resolved resonant photoemission to map local spin and orbital excitations in itinerant ferromagnets, revealing complex entangled excitations and chiral wavefronts.

Contribution

It presents the first ab-initio modified one-step theory of photoemission to image local spin and orbital flip excitations in itinerant ferromagnets.

Findings

Real space imaging of pure and entangled spin-orbital flip excitations

Detection of chiral vortex-like wavefronts of excited electrons

Resonant photoemission as a sensitive tool for local magnetic tomography

Abstract

A novel method for mapping the local spin and orbital nature of the ground state of a system via corresponding flip excitations in both sectors is proposed based on angle resolved resonant photoemission and related diffraction patterns, presented here for the first time via an ab-initio modified one-step theory of photoemission. The analysis is done on the paradigmatic weak itinerant ferromagnet bcc Fe, whose magnetism, seen as a correlation phenomenon given by the coexistence of localized moments and itinerant electrons, and the non-Fermi liquid behaviour at ambient and extreme conditions both remain unclear. The results offer a real space imaging of local pure spin flip and entangled spin flip-orbital flip excitations (even at energies where spin flip transitions are hidden in quasiparticle peaks) and of chiral, vortex-like wavefronts of excited electrons, depending on the orbital character of the bands and the direction of the local magnetic moment. Such effects, mediated by the hole polarization, make resonant photoemission a promising tool to perform a full tomography of the local magnetic properties of a system with a high sensitivity to localization/correlation, even in itinerant or macroscopically non magnetic systems.