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Nonlocal electron correlations in an itinerant ferromagnet 

we show that in itinerant ferromagnets like cobalt the electron correlations are of nonlocal origin, manifested in a complex self-energy Σσ(E,k) that disperses as function of spin σ, energy E, and momentum vector k. 
Ch. Tusche et al., Nature Communications, Vol. 9 - 1, pp. 3727 (2018)

 



Measured spin-resolved Fermi surface of fcc cobalt. Spin-resolved photoemission intensities in selected sections through the three-dimensional Fermi surface of 18 ML Co/Cu(100) measured at photon energies of hv = 85 eV (a), hv = 70 eV (b), and hv = 50 eV (c). (d) The fcc Brillouin zone together with the corresponding cuts sampled by (a)–(c). According to the 2D colour code at the lower right, red and blue intensities correspond to majority and minority electronic states 

Our understanding of the properties of ferromagnetic materials, widely used in spintronic devices, is fundamentally based on their electronic band structure. However, even for the most simple elemental ferromagnets, electron correlations are prevalent, requiring descriptions of their electronic structure beyond the simple picture of independent quasi-particles. Here, we give evidence that in itinerant ferromagnets like cobalt these electron correlations are of nonlocal origin, manifested in a complex self-energy Σσ(E,k) that disperses as function of spin σ, energy E, and momentum vector k. Together with one-step photoemission calculations, our experiments allow us to quantify the dispersive behaviour of the complex self-energy over the whole Brillouin zone. 
At the same time we observe regions of anomalously large “waterfall”-like band renormalization, previously only attributed to strong electron correlations in high-TC superconductors, making itinerant ferromagnets a paradigmatic test case for the interplay between band structure, magnetism, and many-body correlations

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Nonlocal electron correlations in an itinerant ferromagnet
Tusche Christian, Ellguth Martin, Feyer Vitaliy, Krasyuk Alexander, Wiemann Carsten, Henk Jürgen, Schneider Claus M., Kirschner Jürgen, Nature Communications, Vol. 9 - 1, pp. 3727 (2018), doi: 10.1038/s41467-018-05960-5


 

Ultima modifica il Lunedì, 11 Novembre 2019 17:28