Abstract
The dynamical spin susceptibility in the new-structure-type iron-based superconductor CaKFe4As4 was investigated by using a combination of inelastic neutron scattering (INS) measurements and random phase approximation (RPA) calculations. Powder INS measurements show that the spin resonance at Qres = 1.17(1) Å−1, corresponding to the (π, π) nesting wave vector in tetragonal notation, evolves below Tc. The characteristic energy of the spin resonance Eres = 12.5 meV is smaller than twice the size of the superconducting gap (2Δ). The broad energy feature of the dynamical susceptibility of the spin resonance can be explained by the RPA calculations, in which the different superconducting gaps on different Fermi surfaces are taken into account. Our INS and PRA studies demonstrate that the superconducting pairing nature in CaKFe4As4 is the s± symmetry.
| Original language | English |
|---|---|
| Article number | 093703 |
| Journal | Journal of the Physical Society of Japan |
| Volume | 86 |
| Issue number | 9 |
| DOIs | |
| State | Published - Sep 15 2017 |
Funding
Acknowledgments This research at ORNL’s Spallation Neutron Source was sponsored by the Scientific User Facilities Division, Office of Basic Energy Sciences, U.S. Department of Energy. The calculations were performed on the supercomputing system SGI ICE X at the Japan Atomic Energy Agency. Sample characterization was performed by using the SQUID magnetometer (MPMS, Quantum Design Inc.) at the CROSS user laboratories. Travel expenses for the ARCS experiment were provided by the General User Program for Neutron Scattering Experiments, Institute for Solid State Physics, The University of Tokyo (Proposal Number GPTAS:16913), at JRR-3, Japan Atomic Energy Agency, Tokai, Japan. The present work was partially supported by JSPS KAKENHI Grant Numbers JP15K00178, JP15K17686, JP15K17712, and JP17K14349. This study was also supported by the “Topological Materials Science” (No. JP16H00995) KAKENHI on Innovative Areas from JSPS of Japan and the Cooperative Research Program of “Network Joint Research Center for Materials and Devices” (2015143 and 20161060).