1
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Yang Y, Wang Q, Duan S, Wo H, Huang C, Wang S, Gu L, Xiang D, Qian D, Zhao J, Zhang W. Anomalous Contribution to the Nematic Electronic States from the Structural Transition in FeSe Revealed by Time- and Angle-Resolved Photoemission Spectroscopy. PHYSICAL REVIEW LETTERS 2022; 128:246401. [PMID: 35776468 DOI: 10.1103/physrevlett.128.246401] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/19/2021] [Revised: 01/16/2022] [Accepted: 05/24/2022] [Indexed: 06/15/2023]
Abstract
High-resolution time- and angle-resolved photoemission measurements were made on FeSe superconductors. With ultrafast photoexcitation, two critical excitation fluences that correspond to two ultrafast electronic phase transitions were found only in the d_{yz}-orbit-derived band near the Brillouin-zone center within our time and energy resolution. Upon comparison to the detailed temperature dependent measurements, we conclude that there are two equilibrium electronic phase transitions (at approximately 90 and 120 K) above the superconducting transition temperature, and an anomalous contribution on the scale of 10 meV to the nematic states from the structural transition is experimentally determined. Our observations strongly suggest that the electronic phase transition at 120 K must be taken into account in the energy band development of FeSe, and, furthermore, the contribution of the structural transition plays an important role in the nematic phase of iron-based high-temperature superconductors.
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Affiliation(s)
- Yuanyuan Yang
- Key Laboratory of Artificial Structures and Quantum Control (Ministry of Education), Shenyang National Laboratory for Materials Science, School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Qisi Wang
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433, China
| | - Shaofeng Duan
- Key Laboratory of Artificial Structures and Quantum Control (Ministry of Education), Shenyang National Laboratory for Materials Science, School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Hongliang Wo
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433, China
| | - Chaozhi Huang
- Key Laboratory of Artificial Structures and Quantum Control (Ministry of Education), Shenyang National Laboratory for Materials Science, School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Shichong Wang
- Key Laboratory of Artificial Structures and Quantum Control (Ministry of Education), Shenyang National Laboratory for Materials Science, School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Lingxiao Gu
- Key Laboratory of Artificial Structures and Quantum Control (Ministry of Education), Shenyang National Laboratory for Materials Science, School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Dao Xiang
- Key Laboratory for Laser Plasmas (Ministry of Education), School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240, China
- Tsung-Dao Lee Institute, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Dong Qian
- Key Laboratory of Artificial Structures and Quantum Control (Ministry of Education), Shenyang National Laboratory for Materials Science, School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240, China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
| | - Jun Zhao
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433, China
- Institute of Nanoelectronics and Quantum Computing, Fudan University, Shanghai 200433, China
| | - Wentao Zhang
- Key Laboratory of Artificial Structures and Quantum Control (Ministry of Education), Shenyang National Laboratory for Materials Science, School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240, China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
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2
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Kissikov T, Sarkar R, Lawson M, Bush BT, Timmons EI, Tanatar MA, Prozorov R, Bud'ko SL, Canfield PC, Fernandes RM, Curro NJ. Uniaxial strain control of spin-polarization in multicomponent nematic order of BaFe 2As 2. Nat Commun 2018. [PMID: 29535323 PMCID: PMC5849640 DOI: 10.1038/s41467-018-03377-8] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
The iron-based high temperature superconductors exhibit a rich phase diagram reflecting a complex interplay between spin, lattice, and orbital degrees of freedom. The nematic state observed in these compounds epitomizes this complexity, by entangling a real-space anisotropy in the spin fluctuation spectrum with ferro-orbital order and an orthorhombic lattice distortion. A subtle and less-explored facet of the interplay between these degrees of freedom arises from the sizable spin-orbit coupling present in these systems, which translates anisotropies in real space into anisotropies in spin space. We present nuclear magnetic resonance studies, which reveal that the magnetic fluctuation spectrum in the paramagnetic phase of BaFe2As2 acquires an anisotropic response in spin-space upon application of a tetragonal symmetry-breaking strain field. Our results unveil an internal spin structure of the nematic order parameter, indicating that electronic nematic materials may offer a route to magneto-mechanical control. A fundamental understanding of nematic order is one of the most important issues to explore in the high temperature superconductors. Here, the authors unveil an internal spin structure of the nematic order in BaFe2As2 by using nuclear magnetic resonance under precisely controlled tunable strain.
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Affiliation(s)
- T Kissikov
- Department of Physics, University of California, Davis, CA, 95616, USA
| | - R Sarkar
- Institute for Solid State Physics, TU Dresden, D-01069, Dresden, Germany
| | - M Lawson
- Department of Physics, University of California, Davis, CA, 95616, USA
| | - B T Bush
- Department of Physics, University of California, Davis, CA, 95616, USA
| | - E I Timmons
- Ames Laboratory U.S. DOE and Department of Physics and Astronomy, Iowa State University, Ames, IA, 50011, USA
| | - M A Tanatar
- Ames Laboratory U.S. DOE and Department of Physics and Astronomy, Iowa State University, Ames, IA, 50011, USA
| | - R Prozorov
- Ames Laboratory U.S. DOE and Department of Physics and Astronomy, Iowa State University, Ames, IA, 50011, USA
| | - S L Bud'ko
- Ames Laboratory U.S. DOE and Department of Physics and Astronomy, Iowa State University, Ames, IA, 50011, USA
| | - P C Canfield
- Ames Laboratory U.S. DOE and Department of Physics and Astronomy, Iowa State University, Ames, IA, 50011, USA
| | - R M Fernandes
- School of Physics and Astronomy, University of Minnesota, Minneapolis, MN, 55455, USA
| | - N J Curro
- Department of Physics, University of California, Davis, CA, 95616, USA.
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3
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Böhmer AE, Kreisel A. Nematicity, magnetism and superconductivity in FeSe. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2018; 30:023001. [PMID: 29240560 DOI: 10.1088/1361-648x/aa9caa] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Iron-based superconductors are well known for their complex interplay between structure, magnetism and superconductivity. FeSe offers a particularly fascinating example. This material has been intensely discussed because of its extended nematic phase, whose relationship with magnetism is not obvious. Superconductivity in FeSe is highly tunable, with the superconducting transition temperature, T c, ranging from 8 K in bulk single crystals at ambient pressure to almost 40 K under pressure or in intercalated systems, and to even higher temperatures in thin films. In this topical review, we present an overview of nematicity, magnetism and superconductivity, and discuss the interplay of these phases in FeSe. We focus on bulk FeSe and the effects of physical pressure and chemical substitutions as tuning parameters. The experimental results are discussed in the context of the well-studied iron-pnictide superconductors and interpretations from theoretical approaches are presented.
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Affiliation(s)
- Anna E Böhmer
- Ames Laboratory, US DOE, Ames, IA 50011, United States of America
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4
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Frustration-driven C 4 symmetric order in a naturally-heterostructured superconductor Sr 2VO 3FeAs. Nat Commun 2017; 8:2167. [PMID: 29255140 PMCID: PMC5735138 DOI: 10.1038/s41467-017-02327-0] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2017] [Accepted: 11/15/2017] [Indexed: 11/08/2022] Open
Abstract
A subtle balance between competing interactions in iron-based superconductors (FeSCs) can be tipped by additional interfacial interactions in a heterostructure, often inducing exotic phases with unprecedented properties. Particularly when the proximity-coupled layer is magnetically active, rich phase diagrams are expected in FeSCs, but this has not been explored yet. Here, using high-accuracy 75As and 51V nuclear magnetic resonance measurements, we investigate an electronic phase that emerges in the FeAs layer below T 0 ~ 155 K of Sr2VO3FeAs, a naturally assembled heterostructure of an FeSC and a Mott-insulating vanadium oxide. We find that frustration of the otherwise dominant Fe stripe and V Neel fluctuations via interfacial coupling induces a charge/orbital order in the FeAs layers, without either static magnetism or broken C 4 symmetry, while suppressing the Neel antiferromagnetism in the SrVO3 layers. These findings demonstrate that the magnetic proximity coupling stabilizes a hidden order in FeSCs, which may also apply to other strongly correlated heterostructures.
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5
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Dichotomy between in-plane magnetic susceptibility and resistivity anisotropies in extremely strained BaFe 2As 2. Nat Commun 2017; 8:504. [PMID: 28894127 PMCID: PMC5593886 DOI: 10.1038/s41467-017-00712-3] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2017] [Accepted: 07/21/2017] [Indexed: 11/08/2022] Open
Abstract
High-temperature superconductivity in the Fe-based materials emerges when the antiferromagnetism of the parent compounds is suppressed by either doping or pressure. Closely connected to the antiferromagnetic state are entangled orbital, lattice, and nematic degrees of freedom, and one of the major goals in this field has been to determine the hierarchy of these interactions. Here we present the direct measurements and the calculations of the in-plane uniform magnetic susceptibility anisotropy of BaFe2As2, which help in determining the above hierarchy. The magnetization measurements are made possible by utilizing a simple method for applying a large symmetry-breaking strain, based on differential thermal expansion. In strong contrast to the large resistivity anisotropy above the antiferromagnetic transition at T N, the anisotropy of the in-plane magnetic susceptibility develops largely below T N. Our results imply that lattice and orbital degrees of freedom play a subdominant role in these materials.Interplay between lattice, orbital, magnetic and nematic degrees of freedom is crucial for the superconductivity in Fe-based materials. Here, the authors demonstrate the subdominant roles of pure lattice distortions and/or orbital ordering in BaFe2As2 by characterizing the in-plane magnetic susceptibility anisotropy.
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6
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Zhang W, Park JT, Lu X, Wei Y, Ma X, Hao L, Dai P, Meng ZY, Yang YF, Luo H, Li S. Effect of Nematic Order on the Low-Energy Spin Fluctuations in Detwinned BaFe_{1.935}Ni_{0.065}As_{2}. PHYSICAL REVIEW LETTERS 2016; 117:227003. [PMID: 27925732 DOI: 10.1103/physrevlett.117.227003] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/22/2016] [Indexed: 06/06/2023]
Abstract
The origin of nematic order remains one of the major debates in iron-based superconductors. In theories based on spin nematicity, one major prediction is that the spin-spin correlation length at (0,π) should decrease with decreasing temperature below the structural transition temperature T_{s}. Here, we report inelastic neutron scattering studies on the low-energy spin fluctuations in BaFe_{1.935}Ni_{0.065}As_{2} under uniaxial pressure. Both intensity and spin-spin correlation start to show anisotropic behavior at high temperature, while the reduction of the spin-spin correlation length at (0,π) happens just below T_{s}, suggesting the strong effect of nematic order on low-energy spin fluctuations. Our results favor the idea that treats the spin degree of freedom as the driving force of the electronic nematic order.
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Affiliation(s)
- Wenliang Zhang
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - J T Park
- Heinz Maier-Leibnitz Zentrum (MLZ), Technische Universität München, D-85748 Garching, Germany
| | - Xingye Lu
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Yuan Wei
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Xiaoyan Ma
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Lijie Hao
- China Institute of Atomic Energy, Beijing 102413, China
| | - Pengcheng Dai
- Department of Physics and Astronomy, Rice University, Houston, Texas 77005-1827, USA
| | - Zi Yang Meng
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Yi-Feng Yang
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- Collaborative Innovation Center of Quantum Matter, Beijing 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100190, China
| | - Huiqian Luo
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Shiliang Li
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- Collaborative Innovation Center of Quantum Matter, Beijing 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100190, China
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7
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Krzton-Maziopa A, Svitlyk V, Pomjakushina E, Puzniak R, Conder K. Superconductivity in alkali metal intercalated iron selenides. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2016; 28:293002. [PMID: 27248118 DOI: 10.1088/0953-8984/28/29/293002] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Alkali metal intercalated iron selenide superconductors A x Fe2-y Se2 (where A = K, Rb, Cs, Tl/K, and Tl/Rb) are characterized by several unique properties, which were not revealed in other superconducting materials. The compounds crystallize in overall simple layered structure with FeSe layers intercalated with alkali metal. The structure turned out to be pretty complex as the existing Fe-vacancies order below ~550 K, which further leads to an antiferromagnetic ordering with Néel temperature fairly above room temperature. At even lower temperatures a phase separation is observed. While one of these phases stays magnetic down to the lowest temperatures the second is becoming superconducting below ~30 K. All these effects give rise to complex relationships between the structure, magnetism and superconductivity. In particular the iron vacancy ordering, linked with a long-range magnetic order and a mesoscopic phase separation, is assumed to be an intrinsic property of the system. Since the discovery of superconductivity in those compounds in 2010 they were investigated very extensively. Results of the studies conducted using a variety of experimental techniques and performed during the last five years were published in hundreds of reports. The present paper reviews scientific work concerning methods of synthesis and crystal growth, structural and superconducting properties as well as pressure investigations.
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Affiliation(s)
- A Krzton-Maziopa
- Faculty of Chemistry, Warsaw University of Technology, Noakowskiego 3, PL-00-664 Warsaw, Poland
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8
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Liu J, Wang J, Luo W, Sheng J, Wang A, Chen X, Danilkin SA, Bao W. The influence of the structural transition on magnetic fluctuations in NaFeAs. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2016; 28:27LT01. [PMID: 27213626 DOI: 10.1088/0953-8984/28/27/27lt01] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
NaFeAs belongs to a class of Fe-based superconductors which have parent compounds that show separated structural and magnetic transitions. Effects of the structural transition on spin dynamics therefore can be investigated separately from the magnetic transition. A plateau in dynamic spin response is observed in a critical region around the structural transition temperature T S. It is interpreted as being due to the stiffening of spin fluctuations along the in-plane magnetic hard axis due to the d xz and d yz orbital ordering. The appearance of anisotropic spin dynamics in the critical region above the T S at T (*) offers a dynamic magnetic scattering mechanism for anisotropic electronic properties in the commonly referred 'nematic phase'.
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Affiliation(s)
- Juanjuan Liu
- Department of Physics, Renmin University of China, Beijing 100872, People's Republic of China
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9
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Liu X, Li Y, Wan J, Li Z, Pang H. Phase separation in Ca(1-x)La(x)Fe₂As₂ superconductors: a ⁵⁷Fe Mössbauer study. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2016; 28:125701. [PMID: 26910879 DOI: 10.1088/0953-8984/28/12/125701] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
We report a detailed 57Fe Mössbauer study of lanthanum doped CaFe2As2 superconductors. The quadrupole splitting distribution (QSD) method was adopted to analyze the Mössbauer spectra of Ca(1-x) La(x)Fe2As2 (x = 0.2, 0.3) single crystals. For both compounds we observed two QSD contributions centered at 0.31 mm s(-1) and -0.32 mm s(-1) at room temperature. The first principles calculations of the electronic structures and the electric field gradient (EFG) of Ca(1-y)La(y)Fe2As2 model systems reveal that the EFG changes from positive to negative with increasing dopant concentration, indicating that the La atoms distribute heterogeneously in the compounds. The two QSD components behave differently with decreasing temperature. The minority La-rich phase undergoes superconducting transition, while short range spin fluctuations and/or spin-phonon coupling appear in the majority La-poor phase. Our experiments provide new evidence of the phase separation picture at low temperatures in Ca(1-x)La(x)Fe2As2 superconductors.
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10
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Song G, Kusumi R, Kimura F, Kimura T, Deguchi K, Ohki S, Fujito T, Simizu T. Single-crystal NMR approach for determining chemical shift tensors from powder samples via magnetically oriented microcrystal arrays. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2015; 255:28-33. [PMID: 25898399 DOI: 10.1016/j.jmr.2015.03.009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/25/2014] [Revised: 03/10/2015] [Accepted: 03/15/2015] [Indexed: 06/04/2023]
Abstract
The single-crystal rotation technique was applied to magnetically oriented microcrystal arrays (MOMAs) of cellobiose (monoclinic) to determine the principal values and principal axes of the chemical shift tensors of C1 and C1' carbons. Rotations were performed about the magnetic χ1, χ2, and χ3 axes of MOMA, and the measurements were taken at six different orientations with respect to the applied magnetic field. Under these rotations, crowded peaks were reduced and the peaks for the C1 and C1' carbons were identified by comparing with simulation results. Six components of the chemical shift tensor expressed with respect to the magnetic χ1χ2χ3-frame were determined. The tensors thus obtained were transformed into those relative to the molecular frame.
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Affiliation(s)
- Guangjie Song
- Division of Forest and Biomaterials Science, Kyoto University, Kyoto 606-8502, Japan
| | - Ryosuke Kusumi
- Division of Forest and Biomaterials Science, Kyoto University, Kyoto 606-8502, Japan
| | - Fumiko Kimura
- Division of Forest and Biomaterials Science, Kyoto University, Kyoto 606-8502, Japan
| | - Tsunehisa Kimura
- Division of Forest and Biomaterials Science, Kyoto University, Kyoto 606-8502, Japan.
| | - Kenzo Deguchi
- National Institute for Materials Science, Tsukuba, Ibaraki 305-0003, Japan
| | - Shinobu Ohki
- National Institute for Materials Science, Tsukuba, Ibaraki 305-0003, Japan
| | - Teruaki Fujito
- National Institute for Materials Science, Tsukuba, Ibaraki 305-0003, Japan
| | - Tadashi Simizu
- National Institute for Materials Science, Tsukuba, Ibaraki 305-0003, Japan
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11
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Zhang Q, Fernandes RM, Lamsal J, Yan J, Chi S, Tucker GS, Pratt DK, Lynn JW, McCallum RW, Canfield PC, Lograsso TA, Goldman AI, Vaknin D, McQueeney RJ. Neutron-scattering measurements of spin excitations in LaFeAsO and Ba(Fe(0.953)Co(0.047))(2)As(2): evidence for a sharp enhancement of spin fluctuations by nematic order. PHYSICAL REVIEW LETTERS 2015; 114:057001. [PMID: 25699463 DOI: 10.1103/physrevlett.114.057001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/08/2014] [Indexed: 06/04/2023]
Abstract
Inelastic neutron scattering is employed to investigate the impact of electronic nematic order on the magnetic spectra of LaFeAsO and Ba(Fe(0.953)Co(0.047))(2)As(2). These materials are ideal to study the paramagnetic-nematic state, since the nematic order, signaled by the tetragonal-to-orthorhombic transition at T(S), sets in well above the stripe antiferromagnetic ordering at T(N). We find that the temperature-dependent dynamic susceptibility displays an anomaly at T(S) followed by a sharp enhancement in the spin-spin correlation length, revealing a strong feedback effect of nematic order on the low-energy magnetic spectrum. Our findings can be consistently described by a model that attributes the structural or nematic transition to magnetic fluctuations, and unveils the key role played by nematic order in promoting the long-range stripe antiferromagnetic order in iron pnictides.
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Affiliation(s)
- Qiang Zhang
- Ames Laboratory, Ames, Iowa 50011, USA and Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011, USA
| | - Rafael M Fernandes
- School of Physics and Astronomy, University of Minnesota, Minneapolis, Minnesota 55455, USA
| | - Jagat Lamsal
- Ames Laboratory, Ames, Iowa 50011, USA and Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011, USA
| | - Jiaqiang Yan
- Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - Songxue Chi
- Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - Gregory S Tucker
- Ames Laboratory, Ames, Iowa 50011, USA and Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011, USA
| | - Daniel K Pratt
- NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899-6102, USA
| | - Jeffrey W Lynn
- NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899-6102, USA
| | - R W McCallum
- Ames Laboratory, Ames, Iowa 50011, USA and Department of Materials Sciences and Engineering, Iowa State University, Ames, Iowa 50011, USA
| | - Paul C Canfield
- Ames Laboratory, Ames, Iowa 50011, USA and Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011, USA
| | - Thomas A Lograsso
- Ames Laboratory, Ames, Iowa 50011, USA and Department of Materials Sciences and Engineering, Iowa State University, Ames, Iowa 50011, USA
| | - Alan I Goldman
- Ames Laboratory, Ames, Iowa 50011, USA and Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011, USA
| | - David Vaknin
- Ames Laboratory, Ames, Iowa 50011, USA and Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011, USA
| | - Robert J McQueeney
- Ames Laboratory, Ames, Iowa 50011, USA and Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011, USA and Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
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12
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Baek SH, Efremov DV, Ok JM, Kim JS, van den Brink J, Büchner B. Orbital-driven nematicity in FeSe. NATURE MATERIALS 2015; 14:210-214. [PMID: 25384167 DOI: 10.1038/nmat4138] [Citation(s) in RCA: 75] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/29/2014] [Accepted: 10/09/2014] [Indexed: 06/04/2023]
Abstract
A fundamental and unconventional characteristic of superconductivity in iron-based materials is that it occurs in the vicinity of two other instabilities. In addition to a tendency towards magnetic order, these Fe-based systems have a propensity for nematic ordering: a lowering of the rotational symmetry while time-reversal invariance is preserved. Setting the stage for superconductivity, it is heavily debated whether the nematic symmetry breaking is driven by lattice, orbital or spin degrees of freedom. Here, we report a very clear splitting of NMR resonance lines in FeSe at Tnem = 91 K, far above the superconducting Tc of 9.3 K. The splitting occurs for magnetic fields perpendicular to the Fe planes and has the temperature dependence of a Landau-type order parameter. Spin-lattice relaxation rates are not affected at Tnem, which unequivocally establishes orbital degrees of freedom as driving the nematic order. We demonstrate that superconductivity competes with the emerging nematicity.
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Affiliation(s)
- S-H Baek
- IFW Dresden, Helmholtzstr. 20, 01069 Dresden, Germany
| | - D V Efremov
- IFW Dresden, Helmholtzstr. 20, 01069 Dresden, Germany
| | - J M Ok
- Department of Physics, Pohang University of Science and Technology, Pohang 790-784, Korea
| | - J S Kim
- Department of Physics, Pohang University of Science and Technology, Pohang 790-784, Korea
| | - Jeroen van den Brink
- 1] IFW Dresden, Helmholtzstr. 20, 01069 Dresden, Germany [2] Department of Physics, Technische Universität Dresden, 01062 Dresden, Germany
| | - B Büchner
- 1] IFW Dresden, Helmholtzstr. 20, 01069 Dresden, Germany [2] Department of Physics, Technische Universität Dresden, 01062 Dresden, Germany
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13
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Böhmer AE, Arai T, Hardy F, Hattori T, Iye T, Wolf T, Löhneysen HV, Ishida K, Meingast C. Origin of the tetragonal-to-orthorhombic phase transition in FeSe: a combined thermodynamic and NMR study of nematicity. PHYSICAL REVIEW LETTERS 2015; 114:027001. [PMID: 25635558 DOI: 10.1103/physrevlett.114.027001] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/21/2014] [Indexed: 06/04/2023]
Abstract
The nature of the tetragonal-to-orthorhombic structural transition at T_{s}≈90 K in single crystalline FeSe is studied using shear-modulus, heat-capacity, magnetization, and nuclear magnetic resonance measurements. The transition is shown to be accompanied by a large shear-modulus softening, which is practically identical to that of underdoped Ba(Fe,Co)_{2}As_{2}, suggesting a very similar strength of the electron-lattice coupling. On the other hand, a spin-fluctuation contribution to the spin-lattice relaxation rate is only observed below T_{s}. This indicates that the structural, or "nematic," phase transition in FeSe is not driven by magnetic fluctuations.
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Affiliation(s)
- A E Böhmer
- Institut für Festkörperphysik, Karlsruhe Institute of Technology, 76021 Karlsruhe, Germany
| | - T Arai
- Department of Physics, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan
| | - F Hardy
- Institut für Festkörperphysik, Karlsruhe Institute of Technology, 76021 Karlsruhe, Germany
| | - T Hattori
- Department of Physics, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan
| | - T Iye
- Department of Physics, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan
| | - T Wolf
- Institut für Festkörperphysik, Karlsruhe Institute of Technology, 76021 Karlsruhe, Germany
| | - H V Löhneysen
- Institut für Festkörperphysik, Karlsruhe Institute of Technology, 76021 Karlsruhe, Germany
| | - K Ishida
- Department of Physics, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan
| | - C Meingast
- Institut für Festkörperphysik, Karlsruhe Institute of Technology, 76021 Karlsruhe, Germany
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Takeda H, Imai T, Tachibana M, Gaudet J, Gaulin BD, Saparov BI, Sefat AS. Cu substitution effects on the local magnetic properties of Ba(Fe(1-x)Cu(x))(2)As(2): a site-selective (75)As and (63)Cu NMR study. PHYSICAL REVIEW LETTERS 2014; 113:117001. [PMID: 25259999 DOI: 10.1103/physrevlett.113.117001] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/26/2014] [Indexed: 06/03/2023]
Abstract
We take advantage of the site-selective nature of the ^{75}As and ^{63}Cu NMR techniques to probe the Cu substitution effects on the local magnetic properties of the FeAs planes in Ba(Fe_{1-x}Cu_{x})_{2}As_{2}. We show that the suppression of antiferromagnetic Fe spin fluctuations induced by Cu substitution is weaker than a naive expectation based on a simple rigid band picture, in which each Cu atom would donate three electrons to the FeAs planes. Comparison between ^{63}Cu and ^{75}As NMR data indicates that spin fluctuations are suppressed at the Cu and their neighboring Fe sites in the tetragonal phase, suggesting the strongly local nature of the Cu substitution effects. We attribute the absence of a large superconducting dome in the phase diagram of Ba(Fe_{1-x}Cu_{x})_{2}As_{2} to the emergence of a nearly magnetically ordered FeAs plane under the presence of orthorhombic distortion.
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Affiliation(s)
- Hikaru Takeda
- Department of Physics and Astronomy, McMaster University, Hamilton, Ontario L8S4M1, Canada and Department of Physics, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8602, Japan
| | - Takashi Imai
- Department of Physics and Astronomy, McMaster University, Hamilton, Ontario L8S4M1, Canada and Canadian Institute for Advanced Research, Toronto, Ontario M5G1Z8, Canada
| | - Makoto Tachibana
- Department of Physics and Astronomy, McMaster University, Hamilton, Ontario L8S4M1, Canada and National Institute for Materials Science, Tsukuba, Ibaraki 305-0044, Japan
| | - Jonathan Gaudet
- Department of Physics and Astronomy, McMaster University, Hamilton, Ontario L8S4M1, Canada
| | - Bruce D Gaulin
- Department of Physics and Astronomy, McMaster University, Hamilton, Ontario L8S4M1, Canada and Canadian Institute for Advanced Research, Toronto, Ontario M5G1Z8, Canada
| | - Bayrammurad I Saparov
- Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - Athena S Sefat
- Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
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Fernandes RM, Böhmer AE, Meingast C, Schmalian J. Scaling between magnetic and lattice fluctuations in iron pnictide superconductors. PHYSICAL REVIEW LETTERS 2013; 111:137001. [PMID: 24116808 DOI: 10.1103/physrevlett.111.137001] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/03/2013] [Revised: 08/05/2013] [Indexed: 06/02/2023]
Abstract
The phase diagram of the iron arsenides is dominated by a magnetic and a structural phase transition, which need to be suppressed in order for superconductivity to appear. The proximity between the two transition temperature lines indicates correlation between these two phases, whose nature remains unsettled. Here, we find a scaling relation between nuclear magnetic resonance and shear modulus data in the tetragonal phase of electron-doped Ba(Fe1-xCox)2As2 compounds. Because the former probes the strength of magnetic fluctuations while the latter is sensitive to orthorhombic fluctuations, our results provide strong evidence for a magnetically driven structural transition.
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Affiliation(s)
- Rafael M Fernandes
- School of Physics and Astronomy, University of Minnesota, Minneapolis, Minnesota 55116, USA
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16
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Quantum criticality in electron-doped BaFe2−xNixAs2. Nat Commun 2013; 4:2265. [PMID: 23945701 DOI: 10.1038/ncomms3265] [Citation(s) in RCA: 81] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2013] [Accepted: 07/08/2013] [Indexed: 11/08/2022] Open
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17
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Zhou T, Koutroulakis G, Lodico J, Ni N, Thompson JD, Cava RJ, Brown SE. Antiferromagnetic order in Ca10(Pt3As8)(Fe2As2)5 observed by 75As NMR. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2013; 25:122201. [PMID: 23420320 DOI: 10.1088/0953-8984/25/12/122201] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
75As nuclear magnetic resonance (NMR) measurements carried out on underdoped, non-superconducting Ca10(Pt3As8)(Fe2As2)5 reveal physical properties that are similar but not identical to 122 superconductor parent compounds such as BaFeAs. Results from the single crystal study indicate a phase transition to an antiferromagnetic (AF) state on cooling through T ~ 100 K, albeit nonuniformly. Specifically, the NMR lineshape reflects the presence of staggered hyperfine fields on the As sites associated with a striped AF order. The variation of the internal hyperfine field with temperature suggests that the phase transition to the AF state is discontinuous, and therefore likely coincident with the structural transition inferred from transport experiments.
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Affiliation(s)
- T Zhou
- Department of Physics and Astronomy, UCLA, Los Angeles, CA 90095, USA.
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