Robust upward dispersion of the neutron spin resonance in the heavy fermion superconductor Ce1-xYbxCoIn5

Yu Song; John Van Dyke; I K Lum; B D White; Sooyoung Jang; Duygu Yazici; L Shu; A Schneidewind; Petr Čermák; Y Qiu; M B Maple; Dirk K Morr; Pengcheng Dai

doi:10.1038/ncomms12774

Robust upward dispersion of the neutron spin resonance in the heavy fermion superconductor Ce_1-xYb_xCoIn₅

Nat Commun. 2016 Sep 28:7:12774. doi: 10.1038/ncomms12774.

Authors

Yu Song¹, John Van Dyke², I K Lum^{3

4

5}, B D White^{4

5}, Sooyoung Jang^{3

4

5}, Duygu Yazici^{3

4

5}, L Shu^{6

7}, A Schneidewind⁸, Petr Čermák⁸, Y Qiu⁹, M B Maple^{3

4

5}, Dirk K Morr², Pengcheng Dai¹

Affiliations

¹ Department of Physics and Astronomy, Rice University, Houston, Texas 77005, USA.
² Department of Physics, University of Illinois at Chicago, Chicago, Illinois 60607, USA.
³ Materials Science and Engineering Program, University of California, San Diego, La Jolla, California 92093, USA.
⁴ Department of Physics, University of California, San Diego, La Jolla, California 92093, USA.
⁵ Center for Advanced Nanoscience, University of California, San Diego, La Jolla, California 92093, USA.
⁶ State Key Laboratory of Surface Physics, Department of Physics, Fudan University, Shanghai 200433, China.
⁷ Collaborative Innovation Center of Advanced Microstructures, Nanjing 210093, China.
⁸ Jülich Center for Neutron Science JCNS, Forschungszentrum Jülich GmbH, Outstation at MLZ, D-85747 Garching, Germany.
⁹ NIST Center for Neutron Research, National Institute of Standard and Technology, Gaithersburg, Maryland 20899, USA.

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^±)-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_1-xYb_xCoIn₅ 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 CeCoIn₅, we conclude that the robust upward-dispersing resonance mode in Ce_1-xYb_xCoIn₅ is inconsistent with the downward dispersion predicted within the spin-exciton scenario.