Spin excitations in nickelate superconductors
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August 2020 Vol. 63 No. 8: 287412 https://doi.org/10.1007/s11433-020-1578-3
Spin excitations in nickelate superconductors Tao Zhou1* , Yi Gao2, and ZiDan Wang3* 1 Guangdong
Provincial Key Laboratory of Quantum Engineering and Quantum Materials, Guangdong Provincial Engineering Technology Research Center for Quantum Precision Measurement, School of Physics and Telecommunication Engineering, and Frontier Research Institute for Physics, South China Normal University, Guangzhou 510006, China; 2 Department of Physics and Institute of Theoretical Physics, Nanjing Normal University, Nanjing 210023, China; 3 Department of Physics and HKU-UCAS Joint Institute for Theoretical and Computational Physics at Hong Kong, The University of Hong Kong, Hong Kong 999077, China Received March 7, 2020; accepted May 11, 2020; published online June 23, 2020
Applying a three-band model and the random phase approximation, we theoretically study the spin excitations in nickelate superconductors, which have been newly discovered. The spin excitations were found to be incommensurate in the low energy region. The spin resonance phenomenon emerged as the excitation energy increased. The intensity can be maximized at the incommensurate or commensurate momentum, depending on the out-of-plane momentum. The spin excitations reverted to incommensurate at higher energies. We also discuss the similarities and differences in the spin excitations of nickelate and cuprate superconductors. Our predicted results can be later validated in inelastic neutron scattering experiments. nickelates, superconductivity, d-wave pairing, spin susceptibility PACS number(s): Citation:
74.20.Rp, 74.20.Mn, 74.70.-b
T. Zhou, Y. Gao, and Z. D. Wang, Spin excitations in nickelate superconductors, Sci. https://doi.org/10.1007/s11433-020-1578-3
1 Introduction High-T c cuprate superconductivity was discovered over thirty years ago, but understanding its microscopic mechanism has been a challenging task [1]. Undoubtedly, exploring cuprate analogs has revealed a new family of superconductors and has enhanced our understanding of cuprate superconductor physics [2-4]. The Ni atom is close to the Cu atom on the periodic table. Early efforts realized infinite-layer RNiO2 (R=La, Nd) compounds [5-7], which are isostructural to CaCuO2 [8], a parent compound of cuprate superconductors. The Ni+ in RNiO2 has a 3d9 configuration, similar to the Cu2+ in high-T c cuprate superconductors. Therefore, the nickelates are strong potential candidates of cuprate analogs, *Corresponding authors (Tao Zhou, email: [email protected]; ZiDan Wang, email: [email protected])
China-Phys.
Mech.
Astron. 63, 287412 (2020),
and have attracted considerable attention for this reason [57, 9-14]. However, nickelates differ from cuprates in two respects: RNiO2 may be metallic rather than a magnetic insulator [6, 7, 10-14], and the Ni-d x2 −y2 band in LaNiO2 may mix with the La-5d band at low energies [12, 13]. Very recently, superconductivity with T c in the 9-15 K range was discovered in the Sr doped in
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