Fermi Surface Expansion above Critical Temperature in a Hund Ferromagnet

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-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-C.

Automated summary

Using a cluster extension of the dynamical mean-field theory, it is shown that strongly correlated metals subject to Hund's physics exhibit significant electronic structure modulations above magnetic transition temperatures. This is mainly due to effective Hund's physics working in momentum space, originating from ferromagnetic fluctuations in the strong-coupling regime.