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TT: Fachverband Tiefe Temperaturen

TT 5: Correlated Electrons: (General) Theory 1

TT 5.10: Vortrag

Montag, 20. März 2017, 12:00–12:15, HSZ 304

Band structure induced electronic correlations in nickel and iron: van-Hove singularities vs. Earth's core conditions — •Andreas Hausoel¹, Michael Karolak¹, Ersoy Sasioglu², Alexander Lichtenstein³, Karsten Held⁴, Andrey Katanin⁵, Alessandro Toschi⁴, and Giorgio Sangiovanni¹ — ¹University of Wuerzburg — ²Research Center Jülich — ³University of Hamburg — ⁴TU Vienna — ⁵Institute of Metal Physics Ekaterinburg

Some Bravais lattices have a particular geometry and can slow down the motion of Bloch electrons: a 'pre-localisation' due to band structure properties. Another known source of electronic localisation in solids is the Coulomb repulsion in partially-filled d- or f-orbitals, which leads to the formation of local magnetic moments. The combination of these two effects has been viewed so far as mainly an academic issue. Here we show with ab-initio calculations of unprecedented accuracy and model studies, that their synergy represents instead the underlying physical mechanism in two of the most important ferromagnets: nickel and iron. Furthermore in nickel, the van-Hove singularity is essential for ferromagnetism to appear. nickel's electron-electron scattering rate is linear in temperature, in violation of the conventional Landau theory of metals. This is true even at Earth's-core conditions, at which iron is instead a good Fermi-liquid. The importance of nickel in models of geomagnetism may therefore be reconsidered.