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TT: Fachverband Tiefe Temperaturen

TT 6: Surface magnetism and magnetic coupling phenomena (joint session MA/O/TT)

TT 6.10: Vortrag

Montag, 1. April 2019, 12:00–12:15, H53

Nonlocal electron correlations in an itinerant ferromagnet — •Christian Tusche^1,2, Martin Ellguth³, Vitaliy Feyer¹, Alexander Krasyuk³, Carsten Wiemann¹, Jürgen Henk⁴, Claus M. Schneider^1,2, and Jürgen Kirschner^3,4 — ¹Forschungszentrum Jülich GmbH, Peter Grünberg Institut (PGI-6), Jülich — ²Fakultät für Physik, Universität Duisburg-Essen, Duisburg — ³Max-Planck-Institut für Mikrostrukturphysik, Halle — ⁴Martin-Luther-Universität Halle-Wittenberg, Halle

A fundamental concept in solid state physics describes the electrons in a solid by the relation of the energy E vs. the crystal momentum k in a band structure of independent quasi particles. However, even for the most simple elemental ferromagnets, electron correlations are prevalent, requiring descriptions of their electronic structure beyond this simple single-electron picture. Our comprehensive measurements of the spectral-function by spin-resolved momentum microscopy show that in itinerant ferromagnets like cobalt these electron correlations are of nonlocal origin. This manifests in a complex self-energy Σ_σ(E,k) that disperses as function of spin σ, energy E, and momentum k. Combining the experiments with one-step photoemission calculations, we quantify the dispersion of the self-energy over the whole Brillouin zone [1]. The observation of nonlocal electron correlations in cobalt substantially affects our understanding of electron interactions, and makes itinerant ferromagnets a paradigmatic test case for the interplay between band structure, magnetism, and correlations.

[1] C. Tusche et al., Nat. Commun. 9, 3727 (2018)