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| iron pnictide | |
|---|---|
| Name | Iron pnictide |
| Type | Superconductor |
| Discovered | 2006–2008 |
| Composition | Iron, pnictogen (arsenic, phosphorus), other metals |
| Crystal system | Tetragonal, orthorhombic variants |
iron pnictide Iron pnictide materials are a class of layered inorganic compounds containing iron and a pnictogen element such as arsenic or phosphorus that exhibit unconventional superconductivity, itinerant magnetism, and complex electronic nematicity. Early studies linked them to high-temperature superconductors and inspired comparative research with cuprates, heavy-fermion systems, and organic superconductors. Research on iron pnictides has involved collaborations across institutions such as University of Tokyo, Stanford University, Max Planck Society, Los Alamos National Laboratory, and RIKEN.
The discovery timeline traces influential work by groups at Hokkaido University, University of Tokyo, and University of Cambridge; pivotal reports from teams led by researchers like those at Prof. Hideo Hosono's group and at ISSP, University of Tokyo catalyzed attention alongside contemporaneous studies at Rice University and Oak Ridge National Laboratory. Early reports of superconductivity in doped iron arsenides prompted rapid follow-up from laboratories including Los Alamos National Laboratory, Fudan University, Kavli Institute for Theoretical Physics, and industrial research at IBM Research. Conferences at venues such as APS March Meeting, Materials Research Society, and ICPS accelerated cross-disciplinary discussion linking to phenomena explored at Harvard University, Cambridge University (UK), and ETH Zurich.
Iron pnictides commonly adopt layered crystal motifs related to the ZrCuSiAs structure and ThCr2Si2 structure, studied in crystallography labs at Max Planck Institute for Solid State Research, Oak Ridge National Laboratory (ORNL), and ISIS Neutron and Muon Source. Families such as 1111, 122, 111, and 11 denote stoichiometries investigated by researchers at University of California, Berkeley, Tohoku University, NIMS, and Argonne National Laboratory. Chemical substitution at pnictogen sites (arsenic, phosphorus), alkaline-earth layers (barium, strontium), and rare-earth oxypnictide blocks (lanthanum, samarium) was explored by teams including University of Tokyo and Zhejiang University to tune lattice parameters and pnictogen height, with structural transitions characterized by groups at European Synchrotron Radiation Facility and SPring-8.
Angle-resolved photoemission spectroscopy (ARPES) performed at facilities like Lawrence Berkeley National Laboratory and Stanford Synchrotron Radiation Lightsource revealed multi-band Fermi surfaces with hole pockets at the zone center and electron pockets at the zone corner, linking to theoretical work at Princeton University, MIT, and Rutgers University. The unconventional pairing symmetry proposals—s±, nodal s-wave, and d-wave—were advanced in theoretical collaborations involving ICFO, CERN, and Perimeter Institute. Measurements by groups at Columbia University and University of Illinois Urbana–Champaign compared superconducting gaps, penetration depth, and quasiparticle interference with models developed at Los Alamos National Laboratory and University of Cambridge (UK).
Neutron scattering experiments at Oak Ridge National Laboratory, Institut Laue-Langevin, and ISIS mapped stripe-like antiferromagnetism and spin-density-wave order competing with superconductivity; these results connected to nematic electronic order studied by teams at Princeton University, University of Bristol, and McMaster University. The interplay of magnetism, nematicity, and superconductivity was debated in workshops at KITP and Cavendish Laboratory, with analyses referencing spin-fluctuation theories from University of Minnesota and orbital-order scenarios from Max Planck Institute for Solid State Research.
Synthesis approaches—solid-state reaction, flux growth, high-pressure methods, and molecular beam epitaxy—were developed at Argonne National Laboratory, Brookhaven National Laboratory, NIST, and University of Tokyo. Prominent families include 1111 (REFeAsO), 122 (AFe2As2), 111 (AFeAs), and 11 (FeSe, FeTe), with chemical tuning explored by groups at University of Science and Technology of China, Tohoku University, and University of Oxford. Thin-film synthesis for device studies was pursued at University of Twente and Rensselaer Polytechnic Institute.
Transport, optical, thermodynamic, and spectroscopic probes performed by teams at MIT, University of Florida, Columbia University, ETH Zurich, and Paul Scherrer Institute documented resistivity anisotropy, Hall effect, infrared conductivity, specific heat anomalies, and NMR Knight shifts. Muon-spin rotation studies at PSI and neutron diffraction at ILL characterized magnetic volume fractions and ordered moments, while scanning tunneling microscopy work at Cornell University and Stanford University imaged gap inhomogeneity and vortex cores.
Applied research into wire fabrication, magnetic sensors, and thin-film Josephson devices engaged institutes such as National Institute for Materials Science, Hitachi, Siemens, and Thales Group. Prospects for cryogenic electronics, high-field magnets, and quantum devices have been evaluated in collaborations involving CEA Saclay, Lawrence Livermore National Laboratory, and European Commission funded consortia, though commercialization faces challenges similar to those encountered historically by IBM Research and General Electric in superconducting technology translation.
Category:Superconductors