Spin resonances in heavy-fermion superconductors

Historically heavy-fermion superconductors have been the first discovered unconventional superconductors and can to some extent be regarded as model systems for high-Tc superconductors. A hallmark of the unconventional superconductivity in high-Tc cuprates has been the observation of a spin resonance in the magnetic excitation spectrum probed by inelastic neutron scattering. We review the situation in heavy-fermion superconductors, the possible existence of a spin resonance in the superconducting state and its implications. •Spin resonances in inelastic neutron scattering are a characteristic of unconventional superconductivity.•Only very few heavy-fermion superconductors are known which show a spin resonance in superconducting state.•Presentation of heavy-fermion superconductors with spin resonance and possible dispersion of resonance mode (with figures).•Some heavy-fermion superconductors without spin resonance are mentioned and possible reasons are given.