CC BY 4.0 UnportedSong, YuWang, WeiyiCao, ChongdeYamani, ZahraXu, YuanjiSheng, YutaoLöser, WolfgangQiu, YimingYang, Yi-fengBirgeneau, Robert J.Dai, Pengcheng2021-08-252021-08-252021https://oa.tib.eu/renate/handle/123456789/6597https://doi.org/10.34657/5644Magnetic fluctuations is the leading candidate for pairing in cuprate, iron-based, and heavy fermion superconductors. This view is challenged by the recent discovery of nodeless superconductivity in CeCu2Si2, and calls for a detailed understanding of the corresponding magnetic fluctuations. Here, we mapped out the magnetic excitations in superconducting (S-type) CeCu2Si2 using inelastic neutron scattering, finding a strongly asymmetric dispersion for E ≲ 1.5 meV, which at higher energies evolves into broad columnar magnetic excitations that extend to E ≳ 5 meV. While low-energy magnetic excitations exhibit marked three-dimensional characteristics, the high-energy magnetic excitations in CeCu2Si2 are almost two-dimensional, reminiscent of paramagnons found in cuprate and iron-based superconductors. By comparing our experimental findings with calculations in the random-phase approximation,we find that the magnetic excitations in CeCu2Si2 arise from quasiparticles associated with its heavy electron band, which are also responsible for superconductivity. Our results provide a basis for understanding magnetism and superconductivity in CeCu2Si2, and demonstrate the utility of neutron scattering in probing band renormalization in heavy fermion metals.enghttps://creativecommons.org/licenses/by/4.0/530Magnetic properties and materialsSuperconducting properties and materialsArticle