中国物理B ›› 2013, Vol. 22 ›› Issue (8): 87405-087405.doi: 10.1088/1674-1056/22/8/087405

所属专题: TOPICAL REVIEW — Iron-based high temperature superconductors

• TOPICAL REVIEW—Iron-based high temperature superconductors • 上一篇    下一篇

Physics picture from neutron scattering study on Fe-based superconductors

鲍威   

  1. Department of Physics, Renmin University of China, Beijing 100872, China
  • 收稿日期:2013-07-04 修回日期:2013-07-12 出版日期:2013-06-27 发布日期:2013-06-27
  • 基金资助:
    Project supported by the National Basic Research Program of China (Grant Nos. 2012CB921700 and 2011CBA00112) and the National Natural Science Foundation of China (Grant Nos. 11034012 and 11190024).

Physics picture from neutron scattering study on Fe-based superconductors

Bao Wei (鲍威)   

  1. Department of Physics, Renmin University of China, Beijing 100872, China
  • Received:2013-07-04 Revised:2013-07-12 Online:2013-06-27 Published:2013-06-27
  • Contact: Bao Wei E-mail:wbao@ruc.edu.cn
  • Supported by:
    Project supported by the National Basic Research Program of China (Grant Nos. 2012CB921700 and 2011CBA00112) and the National Natural Science Foundation of China (Grant Nos. 11034012 and 11190024).

摘要: Neutron scattering, with its ability to measure the crystal structure, the magnetic order, and the structural and magnetic excitations, plays an active role in investigating various families of Fe-based high-Tc superconductors. Three different types of antiferromagnetic orders have been discovered in the Fe plane, but two of them cannot be explained by the spin-densitywave (SDW) mechanism of nesting Fermi surfaces. Noticing the close relation between antiferromagnetic order and lattice distortion in orbital ordering from previous studies on manganites and other oxides, we have advocated orbital ordering as the underlying common mechanism for the structural and antiferromagnetic transitions in the 1111, 122, and 11 parent compounds. We observe the coexistence of antiferromagnetic order and superconductivity in the (Ba,K)Fe2As2 system, when its phase separation is generally accepted. Optimal Tc is proposed to be controlled by the local FeAs4 tetrahedron from our investigation on the 1111 materials. The Bloch phase coherence of the Fermi liquid is found crucial to the occurrence of bulk superconductivity in iron chalcogenides of both the 11 and the 245 families. Iron chalcogenides carry a larger staggered magnetic moment (> 2 μB/Fe) than that in iron pnictides (< 1μB/Fe) in the antiferromagnetic order. Normal state magnetic excitations in the 11 superconductor are of the itinerant nature while in the 245 superconductor the spin-waves of localized moments. The observation of superconducting resonance peak provides a crucial piece of information in current deliberation of the pairing symmetry in Fe-based superconductors.

关键词: orbital ordering, antiferromagnetic order, excitations, structural transition

Abstract: Neutron scattering, with its ability to measure the crystal structure, the magnetic order, and the structural and magnetic excitations, plays an active role in investigating various families of Fe-based high-Tc superconductors. Three different types of antiferromagnetic orders have been discovered in the Fe plane, but two of them cannot be explained by the spin-densitywave (SDW) mechanism of nesting Fermi surfaces. Noticing the close relation between antiferromagnetic order and lattice distortion in orbital ordering from previous studies on manganites and other oxides, we have advocated orbital ordering as the underlying common mechanism for the structural and antiferromagnetic transitions in the 1111, 122, and 11 parent compounds. We observe the coexistence of antiferromagnetic order and superconductivity in the (Ba,K)Fe2As2 system, when its phase separation is generally accepted. Optimal Tc is proposed to be controlled by the local FeAs4 tetrahedron from our investigation on the 1111 materials. The Bloch phase coherence of the Fermi liquid is found crucial to the occurrence of bulk superconductivity in iron chalcogenides of both the 11 and the 245 families. Iron chalcogenides carry a larger staggered magnetic moment (> 2 μB/Fe) than that in iron pnictides (< 1μB/Fe) in the antiferromagnetic order. Normal state magnetic excitations in the 11 superconductor are of the itinerant nature while in the 245 superconductor the spin-waves of localized moments. The observation of superconducting resonance peak provides a crucial piece of information in current deliberation of the pairing symmetry in Fe-based superconductors.

Key words: orbital ordering, antiferromagnetic order, excitations, structural transition

中图分类号:  (Magnetic properties including vortex structures and related phenomena)

  • 74.25.Ha
74.70.-b (Superconducting materials other than cuprates) 78.70.Nx (Neutron inelastic scattering) 74.25.Jb (Electronic structure (photoemission, etc.))