Robust upward dispersion of the neutron spin resonance in the heavy fermion superconductor Ce<sub>1-x</sub>Yb<sub>x</sub>CoIn<sub>5</sub>.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 27677397.
- Also identified by DOI 10.1038/ncomms12774 and PMC identifier 5052703.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
The neutron spin resonance is a collective magnetic excitation that appears in the unconventional copper oxide, iron pnictide and heavy fermion superconductors. Although the resonance is commonly associated with a spin-exciton due to the d(s<sup>±</sup>)-wave symmetry of the superconducting order parameter, it has also been proposed to be a magnon-like excitation appearing in the superconducting state. Here we use inelastic neutron scattering to demonstrate that the resonance in the heavy fermion superconductor Ce<sub>1-x</sub>Yb<sub>x</sub>CoIn<sub>5</sub> with x=0, 0.05 and 0.3 has a ring-like upward dispersion that is robust against Yb-doping. By comparing our experimental data with a random phase approximation calculation using the electronic structure and the momentum dependence of the -wave superconducting gap determined from scanning tunnelling microscopy (STM) for CeCoIn<sub>5</sub>, we conclude that the robust upward-dispersing resonance mode in Ce<sub>1-x</sub>Yb<sub>x</sub>CoIn<sub>5</sub> is inconsistent with the downward dispersion predicted within the spin-exciton scenario.