Song Yu, Van Dyke John, Lum I K, White B D, Jang Sooyoung, Yazici Duygu, Shu L, Schneidewind A, Čermák Petr, Qiu Y, Maple M B, Morr Dirk K, Dai Pengcheng
Department of Physics and Astronomy, Rice University, Houston, Texas 77005, USA.
Department of Physics, University of Illinois at Chicago, Chicago, Illinois 60607, USA.
Nat Commun. 2016 Sep 28;7:12774. doi: 10.1038/ncomms12774.
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 CeYbCoIn 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, we conclude that the robust upward-dispersing resonance mode in CeYbCoIn is inconsistent with the downward dispersion predicted within the spin-exciton scenario.
中子自旋共振是一种集体磁激发，出现在非常规的铜氧化物、铁基磷化物和重费米子超导体中。尽管由于超导序参量的d(s)波对称性，这种共振通常与自旋激子相关，但也有人提出它是超导态中出现的一种类磁振子激发。在这里，我们使用非弹性中子散射来证明，重费米子超导体CeYbCoIn（x = 0、0.05和0.3）中的共振具有类似环状的向上色散，且对Yb掺杂具有鲁棒性。通过将我们的实验数据与使用电子结构以及从CeCoIn的扫描隧道显微镜（STM）确定的s波超导能隙的动量依赖性进行的随机相位近似计算进行比较，我们得出结论，CeYbCoIn中鲁棒的向上色散共振模式与自旋激子情形下预测的向下色散不一致。
