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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, L. Shu, A. Schneidewind, Petr Cermak, Yiming Qiu, M. B. Maple, Dirk K. Morr, Pengcheng Dai


Understanding the origin of unconventional superconductivity in strongly correlated electron materials continues to be at the forefront of modern condensed matter physics [1-5]. In copper oxides [6-8], iron pnictides [9, 10], and heavy fermion [11, 12] superconductors, the appearance of a neutron spin resonance below the superconducting transition temperature Tc suggests that spin-fluctuation mediated pairing is a common thread for different families of unconventional superconductors [2]. Although the resonance has been associated with a spin exciton due to the d(s+-1)-wave symmetry of the superconducting gap [7, 12, 13] or an over damped spin-wave-like excitation revealed in the superconducting state [14, 15], there is no consensus on its micrscopic origin [2, 7, 8, 10]. Here we use inelastic neutron scattering to demonstrate that the resonance in heavy fermion superconductor Ce1-xYbxCoIn5 with x = 0.05, 0.03 [4, 12, 16] has a ring-like upward dispersion, reminiscent of spin waves in CeRhIn5 [17, 18]. The identification of the paramagnon nature of the resonance in Ce1-xYbxCoIn5 suggests that it can no longer be regarded as a signature of the d-wave pairing arising from quasiparticle excitations between the sign reversed d-wave gaps in heavy fermion unconventional superconductors [2].
Nature Physics


heavy fermion superconductor, spin resonance


Song, Y. , Van Dyke, J. , Lum, I. , White, B. , Shu, L. , Schneidewind, A. , Cermak, P. , Qiu, Y. , Maple, M. , Morr, D. and Dai, P. (2016), 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>, Nature Physics, [online], (Accessed June 5, 2023)
Created September 27, 2016, Updated October 12, 2021