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Du Y, Wang JO, Jiang L, Borgna LS, Wang Y, Zheng Y, Hu T. Data analysis method to achieve sub-10 pm spatial resolution using extended X-ray absorption fine-structure spectroscopy. JOURNAL OF SYNCHROTRON RADIATION 2014; 21:756-761. [PMID: 24971971 DOI: 10.1107/s1600577514010406] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/12/2014] [Accepted: 05/07/2014] [Indexed: 06/03/2023]
Abstract
Obtaining sub-10 pm spatial resolution by extended X-ray absorption fine structure (EXAFS) spectroscopy is required in many important fields of research, such as lattice distortion studies in colossal magnetic resistance materials, high-temperature superconductivity materials etc. However, based on the existing EXAFS data analysis methods, EXAFS has a spatial resolution limit of π/2Δk which is larger than 0.1 Å. In this paper a new data analysis method which can easily achieve sub-10 pm resolution is introduced. Theoretically, the resolution limit of the method is three times better than that normally available. The method is examined by numerical simulation and experimental data. As a demonstration, the LaFe1-xCrxO3 system (x = 0, 1/3, 2/3) is studied and the structural information of FeO6 octahedral distortion as a function of Cr doping is resolved directly from EXAFS, where a resolution better than 0.074 Å is achieved.
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Affiliation(s)
- Yonghua Du
- Institute of Chemical and Engineering Sciences, A*STAR, Singapore 627833, Singapore
| | - Jia Ou Wang
- Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, People's Republic of China
| | - Longhua Jiang
- Department of Physics, Pennsylvania State University, University Park, PA 16802, USA
| | | | - Yanfei Wang
- Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, People's Republic of China
| | - Yi Zheng
- Department of Chemistry, National University of Singapore, Singapore 117543, Singapore
| | - Tiandou Hu
- Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, People's Republic of China
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Yu R, Si Q, Goswami P, Abrahams E. Electron Correlation and Spin Dynamics in Iron Pnictides and Chalcogenides. ACTA ACUST UNITED AC 2013. [DOI: 10.1088/1742-6596/449/1/012025] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Lu X, Gretarsson H, Zhang R, Liu X, Luo H, Tian W, Laver M, Yamani Z, Kim YJ, Nevidomskyy AH, Si Q, Dai P. Avoided quantum criticality and magnetoelastic coupling in BaFe(2-x)Ni(x)As2. PHYSICAL REVIEW LETTERS 2013; 110:257001. [PMID: 23829752 DOI: 10.1103/physrevlett.110.257001] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/29/2013] [Indexed: 06/02/2023]
Abstract
We study the structural and magnetic orders in electron-doped BaFe(2-x)Ni(x)As2 by high-resolution synchrotron x-ray and neutron scatterings. Upon Ni doping x, the nearly simultaneous tetragonal-to-orthorhombic structural (T(s)) and antiferromagnetic (T(N)) phase transitions in BaFe2As2 are gradually suppressed and separated, resulting in T(s)>T(N) with increasing x, as was previously observed. However, the temperature separation between T(s) and T(N) decreases with increasing x for x≥0.065, tending toward a quantum bicritical point near optimal superconductivity at x≈0.1. The zero-temperature transition is preempted by the formation of a secondary incommensurate magnetic phase in the region 0.088≲x≲0.104, resulting in a finite value of T(N)≈T(c) + 10 K above the superconducting dome around x≈0.1. Our results imply an avoided quantum critical point, which is expected to strongly influence the properties of both the normal and superconducting states.
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Affiliation(s)
- Xingye Lu
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
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Morosan E, Natelson D, Nevidomskyy AH, Si Q. Strongly correlated materials. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2012; 24:4896-4923. [PMID: 22893361 DOI: 10.1002/adma.201202018] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/20/2012] [Indexed: 06/01/2023]
Abstract
Strongly correlated materials are profoundly affected by the repulsive electron-electron interaction. This stands in contrast to many commonly used materials such as silicon and aluminum, whose properties are comparatively unaffected by the Coulomb repulsion. Correlated materials often have remarkable properties and transitions between distinct, competing phases with dramatically different electronic and magnetic orders. These rich phenomena are fascinating from the basic science perspective and offer possibilities for technological applications. This article looks at these materials through the lens of research performed at Rice University. Topics examined include: Quantum phase transitions and quantum criticality in "heavy fermion" materials and the iron pnictide high temperature superconductors; computational ab initio methods to examine strongly correlated materials and their interface with analytical theory techniques; layered dichalcogenides as example correlated materials with rich phases (charge density waves, superconductivity, hard ferromagnetism) that may be tuned by composition, pressure, and magnetic field; and nanostructure methods applied to the correlated oxides VO₂ and Fe₃O₄, where metal-insulator transitions can be manipulated by doping at the nanoscale or driving the system out of equilibrium. We conclude with a discussion of the exciting prospects for this class of materials.
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Affiliation(s)
- Emilia Morosan
- Department of Physics and Astronomy MS 61, Rice University, 6100 Main St., Houston, TX 77005, USA
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Luo H, Zhang R, Laver M, Yamani Z, Wang M, Lu X, Wang M, Chen Y, Li S, Chang S, Lynn JW, Dai P. Coexistence and competition of the short-range incommensurate antiferromagnetic order with the superconducting state of BaFe(2-x)Ni(x)As2. PHYSICAL REVIEW LETTERS 2012; 108:247002. [PMID: 23004310 DOI: 10.1103/physrevlett.108.247002] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/27/2011] [Revised: 03/12/2012] [Indexed: 06/01/2023]
Abstract
Superconductivity in the iron pnictides develops near antiferromagnetism, and the antiferromagnetic (AF) phase appears to overlap with the superconducting phase in some materials such as BaFe(2-x)T(x)As2 (where T=Co or Ni). Here we use neutron scattering to demonstrate that genuine long-range AF order and superconductivity do not coexist in BaFe(2-x)Ni(x)As2 near optimal superconductivity. In addition, we find a first-order-like AF-to-superconductivity phase transition with no evidence for a magnetic quantum critical point. Instead, the data reveal that incommensurate short-range AF order coexists and competes with superconductivity, where the AF spin correlation length is comparable to the superconducting coherence length.
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Affiliation(s)
- Huiqian Luo
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
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Sarkar R, Baenitz M, Jesche A, Geibel C, Steglich F. Interplay between Fe 3d and Ce 4f magnetism and Kondo interaction in CeFeAs(1-x)P(x)O probed by 75As and 31P NMR. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2012; 24:135602. [PMID: 22407024 DOI: 10.1088/0953-8984/24/13/135602] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
A detailed (31)P (I = 1/2) and (75)As (I = 3/2) NMR study on polycrystalline CeFeAs(1-x)P(x)O alloys is presented. The magnetism of CeFeAsO changes drastically upon P substitution on the As site. CeFePO is a heavy fermion system without long-range order whereas CeFeAsO exhibits an Fe 3d SDW type of ordering accompanied by a structural transition from tetragonal (TT) to orthorhombic (OT) structure. Furthermore, Ce 4f(1) orders antiferromagnetically (AFM) at low temperature. At the critical concentration where the Fe magnetism is diminished the Ce-Ce interaction changes to a ferromagnetic (FM) type of ordering. Three representative samples of the CeFeAs(1-x)P(x)O (x = 0.05, 0.3 and 0.9) series are systematically investigated. (1) For the x = 0.05 alloy a drastic change of the linewidth at 130 K indicates the AFM-SDW type of ordering of Fe and the structural change from the TT to the OT phase. The linewidth roughly measures the internal field in the ordered state and the transition is most likely first order. The small and nearly constant shift from (31)P and (75)As NMR suggests the presence of competing hyperfine interactions between the nuclear spins and the 4f and 3d ions of Ce and Fe. (2) For the x = 0.3 alloy, the evolution of the Fe-SDW type of order takes place at around 70 K corroborating the results of bulk measurement and μSR. Here we found evidence for phase separation of paramagnetic and magnetic SDW phases. (3) In contrast to the heavy fermion CeFePO for the x = 0.9 alloy a phase transition is found at 2 K. The field-dependent NMR shift gives evidence of FM ordering. Above the ordering the spin-lattice relaxation rate (31)(1/T(1)) shows unconventional, non-Korringa-like behaviour which indicates a complex interplay of Kondo and FM fluctuations.
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Affiliation(s)
- R Sarkar
- Max-Planck Institute for Chemical Physics of Solids, D-01187 Dresden, Germany.
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Giovannetti G, Ortix C, Marsman M, Capone M, van den Brink J, Lorenzana J. Proximity of iron pnictide superconductors to a quantum tricritical point. Nat Commun 2011; 2:398. [PMID: 21772269 PMCID: PMC3160143 DOI: 10.1038/ncomms1407] [Citation(s) in RCA: 68] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2011] [Accepted: 06/20/2011] [Indexed: 11/13/2022] Open
Abstract
In several materials, unconventional superconductivity appears nearby a quantum phase transition where long-range magnetic order vanishes as a function of a control parameter like charge doping, pressure or magnetic field. The nature of the quantum phase transition is of key relevance, because continuous transitions are expected to favour superconductivity, due to strong fluctuations. Discontinuous transitions, on the other hand, are not expected to have a similar role. Here we determine the nature of the magnetic quantum phase transition, which occurs as a function of doping, in the iron-based superconductor LaFeAsO(1-x)F(x). We use constrained density functional calculations that provide ab initio coefficients for a Landau order parameter analysis. The outcome is intriguing, as this material turns out to be remarkably close to a quantum tricritical point, where the transition changes from continuous to discontinuous, and several susceptibilities diverge simultaneously. We discuss the consequences for superconductivity and the phase diagram.
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Affiliation(s)
- Gianluca Giovannetti
- Dipartimento di Fisica, Università di Roma 'La Sapienza', P. Aldo Moro 2, Roma 00185, Italy
- Istituto dei Sistemi Complessi, Consiglio Nazionale delle Ricerche, Dipartimento di Fisica, Università di Roma 'La Sapienza', P. Aldo Moro 2, Roma 00185, Italy
- Istituto Officina dei Materiali, Consiglio Nazionale delle Ricerche, SISSA, Via Bonomea 265, 34136 Trieste, Italy
- Scuola Internazionale Superiore di Studi Avanzati (SISSA), Condensed Matter Sector, Via Bonomea 265, Trieste 34136, SISSA, Via Bonomea 265, 34136 Trieste, Italy
| | - Carmine Ortix
- Institute for Theoretical Solid State Physics, IFW-Dresden, PF 270116, Dresden 01171, Germany
| | - Martijn Marsman
- Faculty of Physics and Center for Computational Materials Science, University Vienna, Sensengasse 8/12, Vienna A-1090, Austria
| | - Massimo Capone
- Dipartimento di Fisica, Università di Roma 'La Sapienza', P. Aldo Moro 2, Roma 00185, Italy
- Istituto Officina dei Materiali, Consiglio Nazionale delle Ricerche, SISSA, Via Bonomea 265, 34136 Trieste, Italy
- Scuola Internazionale Superiore di Studi Avanzati (SISSA), Condensed Matter Sector, Via Bonomea 265, Trieste 34136, SISSA, Via Bonomea 265, 34136 Trieste, Italy
| | - Jeroen van den Brink
- Institute for Theoretical Solid State Physics, IFW-Dresden, PF 270116, Dresden 01171, Germany
| | - José Lorenzana
- Dipartimento di Fisica, Università di Roma 'La Sapienza', P. Aldo Moro 2, Roma 00185, Italy
- Istituto dei Sistemi Complessi, Consiglio Nazionale delle Ricerche, Dipartimento di Fisica, Università di Roma 'La Sapienza', P. Aldo Moro 2, Roma 00185, Italy
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Abrahams E, Si Q. Quantum criticality in the iron pnictides and chalcogenides. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2011; 23:223201. [PMID: 21593557 DOI: 10.1088/0953-8984/23/22/223201] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Superconductivity in the iron pnictides and chalcogenides arises at the border of antiferromagnetism, which raises the question of the role of quantum criticality. In this topical review, we describe the theoretical work that led to the prediction of a magnetic quantum critical point arising out of a competition between electronic localization and itinerancy, and the proposal for accessing it by using isoelectronic P substitution for As in the undoped iron pnictides. We go on to compile the emerging experimental evidence in support of the existence of such a quantum critical point in isoelectronically tuned iron pnictides. We close by discussing the implications of these results for the physics of the iron pnictides and chalcogenides.
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Affiliation(s)
- Elihu Abrahams
- Department of Physics and Astronomy, University of California Los Angeles, Los Angeles, CA 90095, USA.
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Johrendt D, Hosono H, Hoffmann RD, Pöttgen R. Structural chemistry of superconducting pnictides and pnictide oxides with layered structures. ACTA ACUST UNITED AC 2011. [DOI: 10.1524/zkri.2011.1363] [Citation(s) in RCA: 79] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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Nakai Y, Iye T, Kitagawa S, Ishida K, Ikeda H, Kasahara S, Shishido H, Shibauchi T, Matsuda Y, Terashima T. Unconventional superconductivity and antiferromagnetic quantum critical behavior in the isovalent-doped BaFe2(As1-xPx)2. PHYSICAL REVIEW LETTERS 2010; 105:107003. [PMID: 20867541 DOI: 10.1103/physrevlett.105.107003] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/17/2010] [Indexed: 05/29/2023]
Abstract
Spin dynamics evolution of BaFe2(As(1-x)Px){2} was probed as a function of P concentration via 31P NMR. Our NMR study reveals that two-dimensional antiferromagnetic (AF) fluctuations are notably enhanced with little change in static susceptibility on approaching the AF phase from the superconducting dome. Moreover, the magnetically ordered temperature θ deduced from the relaxation rate vanishes at optimal doping. These results provide clear-cut evidence for a quantum-critical point, suggesting that the AF fluctuations associated with the quantum-critical point play a central role in the high-T(c) superconductivity.
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Affiliation(s)
- Y Nakai
- Department of Physics, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan.
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