High-energy magnetic excitations from heavy quasiparticles in CeCu${}_2$Si${}_2$

Abstract

Magnetic 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 CeCu${}_2$Si${}_2$, and calls for a detailed understanding of the corresponding magnetic fluctuations. Here, we mapped out the magnetic excitations in \ys{superconducting (S-type)} CeCu${}_2$Si${}_2$ using inelastic neutron scattering, finding a strongly asymmetric dispersion for $E\lesssim 1.5$~meV, which at higher energies evolve into broad columnar magnetic excitations that extend to $E\gtrsim 5$ meV. While low-energy magnetic excitations exhibit marked three-dimensional characteristics, the high-energy magnetic excitations in CeCu${}_2$Si${}_2$ 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 CeCu${}_2$Si${}_2$ 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 CeCu${}_2$Si${}_2$, and demonstrate the utility of neutron scattering in probing band renormalization in heavy fermion metals.

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Cited by in corpus (7)

• Neutron spectroscopy evidence on the dual nature of magnetic excitations in a van der Waals metallic ferromagnet Fe${}_{2.72}$GeTe${}_2$
• Unconventional fully-gapped superconductivity in the heavy-fermion metal CeCu${}_2$Si${}_2$
• Fractional and composite excitations of antiferromagnetic quantum spin trimer chains
• Quantum phase transitions and composite excitations of antiferromagnetic spin trimer chains in a magnetic field
• Emergent ferromagnetic ladder excitations in heavy fermion superconductor CeSb${}_2$
• CeCu${}_2$Si${}_2$ and YbRh${}_2$Si${}_2$: Strange Cases of Heavy-Fermion Superconductivity
• First-Principles Study of the Fermi Surface Topology of CeCu${}_2$Si${}_2$