Magnetic excitations of a nodally-hybridized heavy-fermion semimetal: application to CeNiSn

We examine the magnetic excitations of an Anderson lattice model with a V-shaped pseudogap arising from nodal hybridization. The model produces a V-shaped pseudogap in the electronic density of states near the Fermi energy. It lies close to an antiferromagnetic (AFM) quantum critical point and features low-dimensional Fermi surfaces, aligning with experimental observations of CeNiSn. The Anderson lattice model with nodal hybridization exhibits degenerate pairs of one-dimensional Fermi surfaces located at the center of the pseudogap. At energies slightly away from the Fermi energy, the constant-energy cuts evolve into small-area tori. We calculate both the static and dynamic magnetic susceptibilities, revealing distinct types of magnetic excitations. Analysis of the susceptibility indicates that the dynamic exponent at the quantum critical point isz=1, in contrast to the usual valuez=2, found for metallic AFM quantum critical points. Since the calculated magnetic spectrum compares favorably with inelastic neutron scattering data on CeNiSn, the model may help resolve ongoing controversies in the interpretation of such experiments. Finally, we propose that the hypothesis of anisotropic hybridization can be tested via tunneling spectroscopy at sites adjacent to substitutional impurities.