Ferromagnetic instability in itinerant fcc lattice electron systems with higher-order van Hove singularities: Functional renormalization group study

We investigate the possibility of ferromagnetic ordering in non-degenerate Hubbard model on face-centered cubic lattice within functional renormalization group technique using temperature as a scale parameter. assume relations between nearest, next-nearest, and next-next-nearest hopping parameters providing higher order (giant) van Hove singularity density states. The instability formation with lowering is described consistently one-loop approximation for one-particle irreducible vertex two-particle electron interaction. chemical potential versus phase diagrams are calculated. find only sufficiently strong divergence states fillings vicinity singularity. obtained Curie more than an magnitude smaller results random-phase approximation. main origin suppression ferromagnetism screening interaction particle-particle channel. also do not pronounced tendency towards incommensurate when Fermi level moved away from singularity, such that first quantum transitions ferro- to paramagnetic obtained.