Non-Fermi-liquid behavior and Fermi-surface expansion induced by van Hove driven ferromagnetic fluctuations: Dual triply irreducible local expansion analysis
Phys. Rev. B 113, 205109 – Published 4 May, 2026
DOI: https://doi.org/10.1103/46h3-sprg
Abstract
We consider the electronic and magnetic properties of the Hubbard model on a square lattice with the Fermi level near van Hove singularity and the ratio of the next-nearest-neighbor and nearest-neighbor hoppings , which favors the ferromagnetic instability. We find that a self-consistent consideration of the ferromagnetic fluctuations within the dual triply irreducible local expansion (D-TRILEX) approach results in the splitting of the electronic spectral function at low temperatures. This splitting exhibits only a weak momentum dependence, and only one of the split bands crosses the Fermi level. As a result, the Fermi surface itself remains unsplit but its area increases, reflecting the presence of non-Fermi-liquid electronic excitations. We show that both the self-consistent account of the nonlocal contributions to the electronic self-energy and the proper treatment of electron interaction vertices in D-TRILEX are important to obtain this behavior.
