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| Iron-based superconductors | |
|---|---|
| Name | Iron-based superconductors |
| Discovered | 2006–2008 |
| Discoverer | Hideo Hosono, Yoshihiko Kamihara |
| Material families | LaFeAsO, BaFe2As2, FeSe, LiFeAs, KFe2Se2 |
| Critical temperature | up to ~56 K |
| Crystal system | tetragonal, orthorhombic, layered |
| Notable properties | unconventional superconductivity, multiband electronic structure, magnetic ordering |
Iron-based superconductors are a class of high-temperature superconducting materials containing layers of iron coordinated by pnictogen or chalcogen elements. First revealed in oxypnictide compounds by Hideo Hosono and Yoshihiko Kamihara, they rapidly spawned extensive research across institutions such as RIKEN, Max Planck Society, and University of Tokyo. Their discovery rekindled parallels with the Bednorz and Müller era and stimulated cross-disciplinary work linking groups at Stanford University, MIT, and University of Cambridge.
Iron-based superconductors emerged from experiments on layered iron pnictides and chalcogenides, producing superconductivity above the temperatures of conventional superconductors and prompting comparisons with the Nobel Prize in Physics-winning field of cuprates associated with J. Georg Bednorz and K. Alex Müller. The class includes families discovered by teams at Tokyo Institute of Technology, Chinese Academy of Sciences, Columbia University, and University of Oxford. Early theoretical responses involved researchers at Princeton University, University of California, Berkeley, National Institute of Standards and Technology (NIST), and Los Alamos National Laboratory.
Common structures include layered tetragonal and orthorhombic lattices found in prototype compounds such as LaFeAsO (1111), BaFe2As2 (122), LiFeAs (111), FeSe (11), and alkali-intercalated phases like KFe2Se2. Structural studies have been driven by facilities at European Synchrotron Radiation Facility (ESRF), Advanced Photon Source (APS), SPring-8, and Diamond Light Source. Neutron diffraction work at Institut Laue-Langevin and Oak Ridge National Laboratory (ORNL) illuminated spin and lattice coupling in materials synthesized at Tohoku University and Zhejiang University. Substitutions at iron, pnictogen, or spacer sites—explored by research groups at University of Science and Technology of China and University of California, Los Angeles (UCLA)—produce variations that map onto families cataloged by work from Paul C. Canfield and Sergey L. Bud'ko.
Angle-resolved photoemission spectroscopy investigations at Stanford Synchrotron Radiation Lightsource (SSRL), Max Planck Institute for Chemical Physics of Solids, and Lawrence Berkeley National Laboratory (LBNL) resolved multiband Fermi surfaces with hole pockets at the Brillouin-zone center and electron pockets at the zone corners; these features motivated pairing theories from groups at Rutgers University, University of Maryland, and University of Tokyo. Competing pairing candidates—s±, s++, and nodal states—were developed by theorists at Duke University, University of Illinois Urbana-Champaign, Harvard University, and University of Minnesota. Spin-fluctuation-mediated pairing models associated with work by Qimiao Si and Andriy H. Nevidomskyy contrasted with orbital-fluctuation proposals from teams at Kavli Institute for Theoretical Physics and Peking University. Quantum oscillation studies by Colin W. Hicks-affiliated groups and density functional theory calculations from John P. Perdew-related collaborations refined band-structure understanding.
Phase diagrams show interplay among antiferromagnetism, nematic order, and superconductivity; mapping has been conducted by laboratories at University of Tokyo, University of Cambridge, University of Geneva, and Tianjin University. Hole and electron doping via chemical substitution (e.g., K for Ba, Co for Fe) investigated by Paul C. Canfield and Pengcheng Dai teams produced dome-shaped superconducting regions similar to trends studied at Brookhaven National Laboratory (BNL) and Argonne National Laboratory (ANL)]. Pressure-induced superconductivity explored at University of Minnesota and National High Magnetic Field Laboratory (NHMFL) further enriched phase diagrams, while uniaxial-stress studies by Ian Fisher's group elucidated nematic susceptibility.
Synthesis methods include solid-state reaction, flux growth, vapor transport, and molecular beam epitaxy pioneered by groups at Oak Ridge National Laboratory (ORNL), Institute of Metal Research (IMR), Chinese Academy of Sciences, and IBM Research. Characterization techniques span muon spin rotation at Paul Scherrer Institute, nuclear magnetic resonance by teams at Kyoto University, transport and Hall measurements at Los Alamos National Laboratory (LANL), and scanning tunneling microscopy by researchers at University of California, Davis and University of British Columbia. Thin-film fabrication enabling device studies was advanced at Tokyo Institute of Technology and University of Illinois at Urbana-Champaign.
Potential applications target high-field magnets, Josephson devices, and energy-saving power components drawing interest from European Organization for Nuclear Research (CERN), ITER Organization, Siemens, and General Electric (GE). Prospects for wires and tapes have been pursued by collaborations involving Fujikura, Sumitomo Electric Industries, SuperOx, and Hyper Tech Research, leveraging fabrication protocols developed at NIMS and National Institute for Materials Science (NIMS). Integration with quantum circuits motivated joint projects between IBM Research, Google Quantum AI, and academic groups at Yale University and University of California, Santa Barbara (UCSB).
Key open questions—resolved through consortia including ERC-funded networks, national labs such as Lawrence Livermore National Laboratory (LLNL), and university centers at MIT and Northwestern University—concern the dominant pairing glue, role of nematicity, impurity effects, and interplay of topology with superconductivity in iron-based materials. Future directions involve targeted materials discovery guided by machine-learning initiatives at Google DeepMind-affiliated research, high-throughput synthesis at SLAC National Accelerator Laboratory, and advanced spectroscopy at ELI-class facilities. Collaborative efforts linking experimentalists from Max Planck Institute for Solid State Research and theorists at Perimeter Institute will continue to shape understanding and technological translation.
Category:Superconductors