Regensburg 2019 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 6: Surface magnetism and magnetic coupling phenomena (joint session MA/O/TT)
TT 6.10: Talk
Monday, April 1, 2019, 12:00–12:15, H53
Nonlocal electron correlations in an itinerant ferromagnet — •Christian Tusche1,2, Martin Ellguth3, Vitaliy Feyer1, Alexander Krasyuk3, Carsten Wiemann1, Jürgen Henk4, Claus M. Schneider1,2, and Jürgen Kirschner3,4 — 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 Σσ(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)