Paramagnons are the collective modes that govern the spin response of nearly magnetic conductors. In some cases they mediate electron pairing leading to superconductivity. This scenario may occur in 2H-NbSe2 monolayers, that feature spin-valley coupling on account of spin-orbit interactions and their lack of inversion symmetry. Here we explore spin anisotropy of paramagnons both for non-centrosymmetric Kane-Mele-Hubbard models for 2H-NbSe2 monolayers described with a DFT-derived tight-binding model. In the infinite wavelength limit we find spatially uniform paramagnons with energies around 1~meV that feature a colossal off-plane uniaxial magnetic anisotropy, with quenched transversal spin response. At finite wave vectors, longitudinal and transverse channels reverse roles: XY fluctuations dominate within a significant portion of the Brillouin zone. Our results show that 2H-NbSe2 is close to a Coulomb-driven in-plane (XY) spin density wave instability.
@article{arxiv.2110.09809,
title = {Ising and XY paramagnons in two-dimensional 2H-NbSe$_2$},
author = {A. T. Costa and M. Costa and J. Fernández-Rossier},
journal= {arXiv preprint arXiv:2110.09809},
year = {2022}
}
Comments
10 pages (6 main text, 4 supplementary material), 10 figures (4 in the main text, 6 in the SM)