We investigate the magnetic orders and excitations in a half-filled Hubbard model that continuously interpolates between the Lieb and kagome lattices. Using self-consistent Hartree-Fock approximation combined with real-time two-particle response functions from the Bethe-Salpeter equation in the random phase approximation, we map the U−t′ phase diagram of the Lieb-kagome lattices, identifying the typical magnetic states and the corresponding magnetic excitation spectra. In addition to gapless Goldstone magnons, the ferrimagnetic and antiferromagnetic symmetry-broken phases also exhibit gapped Higgs magnon bands, which originate from amplitude fluctuations in the order parameter characterizing spontaneous symmetry breaking.
@article{arxiv.2601.07562,
title = {Magnons in multiorbital Hubbard models, from Lieb to kagome},
author = {Teng-Fei Ying and Hugo U. R. Strand and Benjamin T. Zhou and Erik G. C. P. van Loon},
journal= {arXiv preprint arXiv:2601.07562},
year = {2026}
}