Fermi surface expansion above critical temperature in a Hund ferromagnet

Abstract

Using a cluster extension of the dynamical mean-field theory, we show that strongly correlated metals subject to Hund's physics exhibit significant electronic structure modulations above magnetic transition temperatures. In particular, in a ferromagnet having a large local moment due to Hund's coupling (Hund's ferromagnet), the Fermi surface expands even above the Curie temperature ($T_{\mathrm{C}}$) as if a spin polarization occurred. Behind this phenomenon, effective ``Hund's physics'' works in momentum space, originating from ferromagnetic fluctuations in the strong coupling regime. The resulting significantly momentum-dependent (spatially nonlocal) electron correlations induce an electronic structure reconstruction involving a Fermi-surface volume change and a redistribution of the momentum-space occupation. Our finding will give a deeper insight into the physics of Hund's ferromagnets above $T_{\mathrm{C}}$.

arXiv commentMain text: 6 pages, 4 figures. Supplemental Materials: 3 pages, 8 figures

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• Experimental determination of the spin Hamiltonian of the cubic chiral magnet MnSi
• Multi-band D-TRILEX approach to materials with strong electronic correlations