1
|
Luo Y, Marcus GG, Trump BA, Kindervater J, Stone MB, Rodriguez-Rivera JA, Qiu Y, McQueen TM, Tchernyshyov O, Broholm C. Low-energy magnons in the chiral ferrimagnet Cu 2OSeO 3: A coarse-grained approach. Phys Rev B 2020; 101:10.1103/PhysRevB.101.144411. [PMID: 33655091 PMCID: PMC7919739 DOI: 10.1103/physrevb.101.144411] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
We report a comprehensive neutron scattering study of low energy magnetic excitations in the breathing pyrochlore helimagnetic Cu2OSeO3. Fully documenting the four lowest energy magnetic modes that leave the ferrimagnetic configuration of the "strong tetrahedra" intact ( | ℏ ω | < 13 meV), we find gapless quadratic dispersion at the point for energies above 0.2 meV, two doublets separated by 1.6(2) meV at the R point, and a bounded continuum at the X point. Our constrained rigid spin cluster model relates these features to Dzyaloshinskii-Moriya (DM) interactions and the incommensurate helical ground state. Combining conventional spin wave theory with a spin cluster form factor accurately reproduces the measured equal time structure factor through multiple Brillouin zones. An effective spin Hamiltonian describing complex anisotropic intercluster interactions is obtained.
Collapse
Affiliation(s)
- Yi Luo
- Institute for Quantum Matter and Department of Physics and Astronomy, Johns Hopkins University, Baltimore, Maryland 21218, USA
| | - G. G. Marcus
- Institute for Quantum Matter and Department of Physics and Astronomy, Johns Hopkins University, Baltimore, Maryland 21218, USA
| | - B. A. Trump
- NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899-6102, USA
| | - J. Kindervater
- Institute for Quantum Matter and Department of Physics and Astronomy, Johns Hopkins University, Baltimore, Maryland 21218, USA
| | - M. B. Stone
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - J. A. Rodriguez-Rivera
- NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899-6102, USA
- Department of Materials Science and Engineering, University of Maryland, College Park, Maryland 20742, USA
| | - Yiming Qiu
- NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899-6102, USA
| | - T. M. McQueen
- Institute for Quantum Matter and Department of Physics and Astronomy, Johns Hopkins University, Baltimore, Maryland 21218, USA
- Department of Materials Science and Engineering, Johns Hopkins University, Baltimore, Maryland 21218, USA
| | - O. Tchernyshyov
- Institute for Quantum Matter and Department of Physics and Astronomy, Johns Hopkins University, Baltimore, Maryland 21218, USA
| | - C. Broholm
- Institute for Quantum Matter and Department of Physics and Astronomy, Johns Hopkins University, Baltimore, Maryland 21218, USA
- NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899-6102, USA
- Department of Materials Science and Engineering, Johns Hopkins University, Baltimore, Maryland 21218, USA
| |
Collapse
|
2
|
Wu S, Phelan WA, Liu L, Morey JR, Tutmaher JA, Neuefeind JC, Huq A, Stone MB, Feygenson M, Tam DW, Frandsen BA, Trump B, Wan C, Dunsiger SR, McQueen TM, Uemura YJ, Broholm CL. Incommensurate Magnetism Near Quantum Criticality in CeNiAsO. Phys Rev Lett 2019; 122:197203. [PMID: 31144966 DOI: 10.1103/physrevlett.122.197203] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/03/2019] [Indexed: 06/09/2023]
Abstract
We report the discovery of incommensurate magnetism near quantum criticality in CeNiAsO through neutron scattering and zero field muon spin rotation. For T<T_{N1}=8.7(3) K, a second order phase transition yields an incommensurate spin density with a wave vector k=(0.44(4),0,0). For T<T_{N2}=7.6(3) K, we find coplanar commensurate order with a moment of 0.37(5)μ_{B}, reduced to 30% of the saturation moment of the |±1/2⟩ Kramers doublet ground state, which we establish through inelastic neutron scattering. Muon spin rotation in CeNiAs_{1-x}P_{x}O shows the commensurate order only exists for x≤0.1 so we infer the transition at x_{c}=0.4(1) is between an incommensurate longitudinal spin density wave and a paramagnetic Fermi liquid.
Collapse
Affiliation(s)
- Shan Wu
- Department of Physics and Astronomy and Institute for Quantum Matter, Johns Hopkins University, Baltimore, Maryland 21218, USA
- Department of Physics, University of California Berkeley, Berkeley, California 94720, USA
| | - W A Phelan
- Department of Physics and Astronomy and Institute for Quantum Matter, Johns Hopkins University, Baltimore, Maryland 21218, USA
| | - L Liu
- Department of Physics, Columbia University, New York, New York 10027, USA
| | - J R Morey
- Department of Physics and Astronomy and Institute for Quantum Matter, Johns Hopkins University, Baltimore, Maryland 21218, USA
| | - J A Tutmaher
- Department of Physics and Astronomy and Institute for Quantum Matter, Johns Hopkins University, Baltimore, Maryland 21218, USA
| | - J C Neuefeind
- Oak Ridge National Laboratory, Chemical and Engineering Materials Division, Oak Ridge, Tennessee 37831, USA
| | - Ashfia Huq
- Oak Ridge National Laboratory, Neutron Scattering Division, Oak Ridge, Tennessee 37831, USA
| | - Matthew B Stone
- Oak Ridge National Laboratory, Neutron Scattering Division, Oak Ridge, Tennessee 37831, USA
| | - M Feygenson
- Juelich Centre for Neutron Science, Forschungszentrum Juelich GmbH, 52425 Juelich, Germany
| | - David W Tam
- Department of Physics and Astronomy, Rice University, Houston, Texas 77005, USA
| | - Benjamin A Frandsen
- Department of Physics and Astronomy, Brigham Young University, Provo, Utah 84602, USA
| | - Benjamin Trump
- NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA
| | - Cheng Wan
- Department of Physics and Astronomy and Institute for Quantum Matter, Johns Hopkins University, Baltimore, Maryland 21218, USA
| | - S R Dunsiger
- Department of Physics, Simon Fraser University, Burnaby, British Columbia, Canada V5A 1S6
| | - T M McQueen
- Department of Physics and Astronomy and Institute for Quantum Matter, Johns Hopkins University, Baltimore, Maryland 21218, USA
- Department of Materials Science and Engineering, Johns Hopkins University, Baltimore, Maryland 21218, USA
| | - Y J Uemura
- Department of Physics, Columbia University, New York, New York 10027, USA
| | - C L Broholm
- Department of Physics and Astronomy and Institute for Quantum Matter, Johns Hopkins University, Baltimore, Maryland 21218, USA
- Oak Ridge National Laboratory, Neutron Scattering Division, Oak Ridge, Tennessee 37831, USA
- Department of Materials Science and Engineering, Johns Hopkins University, Baltimore, Maryland 21218, USA
| |
Collapse
|
3
|
Liu Q, Yao Q, Kelly ZA, Pasco CM, McQueen TM, Lany S, Zunger A. Electron Doping of Proposed Kagome Quantum Spin Liquid Produces Localized States in the Band Gap. Phys Rev Lett 2018; 121:186402. [PMID: 30444389 DOI: 10.1103/physrevlett.121.186402] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/02/2018] [Revised: 09/18/2018] [Indexed: 06/09/2023]
Abstract
Carrier doping of quantum spin liquids is a long-proposed route to the emergence of high-temperature superconductivity. Electrochemical intercalation in kagome hydroxyl halide materials shows that samples remain insulating across a wide range of electron counts. Here we demonstrate through first-principles density-functional calculations, corrected for self-interaction, the mechanism by which electrons remain localized in various Zn-Cu hydroxyl halides, independent of the chemical identity of the dopant-the formation of polaronic states with attendant lattice displacements and a dramatic narrowing of bandwidth upon electron addition. The same theoretical method applied to electron doping in cuprate Nd_{2}CuO_{4} correctly produces a metallic state when the initially formed polaron dissolves into an extended state. Our general findings explain the insulating behavior in a wide range of "doped" quantum magnets and demonstrate that new quantum spin liquid host materials are needed to realize metallicity borne of a spin liquid.
Collapse
Affiliation(s)
- Qihang Liu
- Renewable and Sustainable Energy Institute, University of Colorado, Boulder, Colorado 80309, USA
- Department of Physics and Shenzhen Institute for Quantum Science and Technology, Southern University of Science and Technology, Shenzhen 518055, China
| | - Qiushi Yao
- Department of Physics and Shenzhen Institute for Quantum Science and Technology, Southern University of Science and Technology, Shenzhen 518055, China
| | - Z A Kelly
- Department of Chemistry, Institute for Quantum Matter, and Department of Physics and Astronomy, The Johns Hopkins University, Baltimore, Maryland 21218, USA
| | - C M Pasco
- Department of Chemistry, Institute for Quantum Matter, and Department of Physics and Astronomy, The Johns Hopkins University, Baltimore, Maryland 21218, USA
| | - T M McQueen
- Department of Chemistry, Institute for Quantum Matter, and Department of Physics and Astronomy, The Johns Hopkins University, Baltimore, Maryland 21218, USA
- Department of Materials Science and Engineering, The Johns Hopkins University, Baltimore, Maryland 21218, USA
| | - S Lany
- National Renewable Energy Laboratory, Golden, Colorado 80401, USA
| | - Alex Zunger
- Renewable and Sustainable Energy Institute, University of Colorado, Boulder, Colorado 80309, USA
| |
Collapse
|
4
|
Trump BA, Koohpayeh SM, Livi KJT, Wen JJ, Arpino KE, Ramasse QM, Brydson R, Feygenson M, Takeda H, Takigawa M, Kimura K, Nakatsuji S, Broholm CL, McQueen TM. Universal geometric frustration in pyrochlores. Nat Commun 2018; 9:2619. [PMID: 29976983 PMCID: PMC6033937 DOI: 10.1038/s41467-018-05033-7] [Citation(s) in RCA: 43] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2017] [Accepted: 06/05/2018] [Indexed: 11/28/2022] Open
Abstract
Materials with the pyrochlore/fluorite structure have diverse technological applications, from magnetism to nuclear waste disposal. Here we report the observation of structural instability present in the pyrochlores A2Zr2O6Oʹ (A = Pr, La) and Yb2Ti2O6Oʹ, that exists despite ideal stoichiometry, ideal cation-ordering, the absence of lone pair effects, and a lack of magnetic order. Though these materials appear to have good long-range order, local structure probes find displacements, of the order of 0.01 nm, within the pyrochlore framework. The pattern of displacements of the A2Oʹ sublattice mimics the entropically-driven fluxional motions characteristic of and well-known in the silica mineral β-cristobalite. The universality of such displacements within the pyrochlore structure adds to the known structural diversity and explains the extreme sensitivity to composition found in quantum spin ices and the lack of ferroelectric behavior in pyrochlores. The family of pyrochlore complex oxides includes many materials of fundamental or practical interest, such as spin ices and dielectrics. Trump et al. show that flexibility of the pyrochlores’ structure leads to local displacements that explain some of their unusual physical properties.
Collapse
Affiliation(s)
- B A Trump
- NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, MD, 20899, USA.,Department of Chemistry, Johns Hopkins University, Baltimore, MD, 21218, USA.,Department of Physics and Astronomy, Institute for Quantum Matter, Johns Hopkins University, Baltimore, MD, 21218, USA
| | - S M Koohpayeh
- Department of Physics and Astronomy, Institute for Quantum Matter, Johns Hopkins University, Baltimore, MD, 21218, USA
| | - K J T Livi
- Department of Materials Science and Engineering, Johns Hopkins University, Baltimore, MD, 21218, USA
| | - J-J Wen
- Department of Physics and Astronomy, Institute for Quantum Matter, Johns Hopkins University, Baltimore, MD, 21218, USA
| | - K E Arpino
- Department of Chemistry, Johns Hopkins University, Baltimore, MD, 21218, USA.,Department of Physics and Astronomy, Institute for Quantum Matter, Johns Hopkins University, Baltimore, MD, 21218, USA
| | - Q M Ramasse
- SuperSTEM Laboratory, STFC Daresbury Campus, Daresbury, WA4 4AD, UK
| | - R Brydson
- School of Chemical and Process Engineering, University of Leeds, Leeds, LS2 9JT, UK
| | - M Feygenson
- Jülich Center for Neutron Science, Forschungszentrum Jülich GmbH, D-52425, Jülich, Germany
| | - H Takeda
- Institute for Solid State Physics, University of Tokyo, Kashiwa, Chiba, 277-8581, Japan
| | - M Takigawa
- Institute for Solid State Physics, University of Tokyo, Kashiwa, Chiba, 277-8581, Japan
| | - K Kimura
- Division of Materials Physics, Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka, 560-8531, Japan
| | - S Nakatsuji
- Institute for Solid State Physics, University of Tokyo, Kashiwa, Chiba, 277-8581, Japan
| | - C L Broholm
- Department of Physics and Astronomy, Institute for Quantum Matter, Johns Hopkins University, Baltimore, MD, 21218, USA.,Department of Materials Science and Engineering, Johns Hopkins University, Baltimore, MD, 21218, USA
| | - T M McQueen
- Department of Chemistry, Johns Hopkins University, Baltimore, MD, 21218, USA. .,Department of Physics and Astronomy, Institute for Quantum Matter, Johns Hopkins University, Baltimore, MD, 21218, USA. .,Department of Materials Science and Engineering, Johns Hopkins University, Baltimore, MD, 21218, USA.
| |
Collapse
|
5
|
Fuhrman WT, Chamorro JR, Alekseev PA, Mignot JM, Keller T, Rodriguez-Rivera JA, Qiu Y, Nikolić P, McQueen TM, Broholm CL. Screened moments and extrinsic in-gap states in samarium hexaboride. Nat Commun 2018; 9:1539. [PMID: 29670117 PMCID: PMC5906653 DOI: 10.1038/s41467-018-04007-z] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2017] [Accepted: 03/27/2018] [Indexed: 11/20/2022] Open
Abstract
Samarium hexaboride (SmB6) is a Kondo insulator, with a narrow gap due to hybridization between localized and conduction electrons. Despite being an insulator, many samples show metal-like properties. Rare-earth purification is exceedingly difficult, and nominally pure samples may contain 2% or more of impurities. Here to determine the effects of rare-earth doping on SmB6, we synthesized and probed a series of gadolinium-doped samples. We found a relationship between specific heat and impurity moment screening which scales systematically. Consistent with this finding, our neutron scattering experiments of a high purity sample of doubly isotopic 154Sm11B6 show no intrinsic excitations below the well-established 13 meV spin-exciton. The result of introducing impurities into a Kondo insulator is incompletely understood, but it is clear from our measurements that there is a systematic relationship between rare-earth impurities and metal-like properties in SmB6. The unconventional behaviour of samarium hexaboride has been difficult to explain in part because of differences between samples. Here the authors use gadolinium to exemplify that hard to avoid impurities introduce a low energy density of states that may explain earlier observations.
Collapse
Affiliation(s)
- W T Fuhrman
- Institute for Quantum Matter and Department of Physics and Astronomy, The Johns Hopkins University, Baltimore, MD, 21218, USA.
| | - J R Chamorro
- Institute for Quantum Matter and Department of Physics and Astronomy, The Johns Hopkins University, Baltimore, MD, 21218, USA.,Department of Chemistry, The Johns Hopkins University, Baltimore, MD, 21218, USA
| | - P A Alekseev
- National Research Centre "Kurchatov Institute", 123182, Moscow, Russia.,National Research Nuclear University "MEPhI", 115409, Moscow, Russia
| | - J-M Mignot
- Laboratoire Léon Brillouin, CEA-CNRS, CEA/Saclay, 91191, Gif sur Yvette, France
| | - T Keller
- Max Planck-Institut für Festkörperforschung, Heisenbergstrasse 1, D-70569, Stuttgart, Germany.,Max Planck Society at the Forschungsneutronenquelle Heinz Maier-Leibnitz (MLZ), D-85747, Garching, Germany
| | - J A Rodriguez-Rivera
- Department of Materials Sciences, University of Maryland, College Park, MD, 20742, USA.,NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, MD, 20899, USA
| | - Y Qiu
- NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, MD, 20899, USA
| | - P Nikolić
- Institute for Quantum Matter and Department of Physics and Astronomy, The Johns Hopkins University, Baltimore, MD, 21218, USA.,School of Physics, Astronomy and Computational Sciences, George Mason University, Fairfax, VA, 22030, USA
| | - T M McQueen
- Institute for Quantum Matter and Department of Physics and Astronomy, The Johns Hopkins University, Baltimore, MD, 21218, USA.,Department of Chemistry, The Johns Hopkins University, Baltimore, MD, 21218, USA.,Department of Materials Science and Engineering, The Johns Hopkins University, Baltimore, MD, 21218, USA
| | - C L Broholm
- Institute for Quantum Matter and Department of Physics and Astronomy, The Johns Hopkins University, Baltimore, MD, 21218, USA.,Department of Materials Science and Engineering, The Johns Hopkins University, Baltimore, MD, 21218, USA
| |
Collapse
|
6
|
Wen JJ, Koohpayeh SM, Ross KA, Trump BA, McQueen TM, Kimura K, Nakatsuji S, Qiu Y, Pajerowski DM, Copley JRD, Broholm CL. Disordered Route to the Coulomb Quantum Spin Liquid: Random Transverse Fields on Spin Ice in Pr_{2}Zr_{2}O_{7}. Phys Rev Lett 2017; 118:107206. [PMID: 28339241 DOI: 10.1103/physrevlett.118.107206] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/27/2016] [Indexed: 06/06/2023]
Abstract
Inelastic neutron scattering reveals a broad continuum of excitations in Pr_{2}Zr_{2}O_{7}, the temperature and magnetic field dependence of which indicate a continuous distribution of quenched transverse fields (Δ) acting on the non-Kramers Pr^{3+} crystal field ground state doublets. Spin-ice correlations are apparent within 0.2 meV of the Zeeman energy. A random phase approximation provides an excellent account of the data with a transverse field distribution ρ(Δ)∝(Δ^{2}+Γ^{2})^{-1}, where Γ=0.27(1) meV. Established during high temperature synthesis due to an underlying structural instability, it appears disorder in Pr_{2}Zr_{2}O_{7} actually induces a quantum spin liquid.
Collapse
Affiliation(s)
- J-J Wen
- Institute for Quantum Matter and Department of Physics and Astronomy, The Johns Hopkins University, Baltimore, Maryland 21218, USA
- Department of Applied Physics, Stanford University, Stanford, California 94305, USA
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, USA
| | - S M Koohpayeh
- Institute for Quantum Matter and Department of Physics and Astronomy, The Johns Hopkins University, Baltimore, Maryland 21218, USA
| | - K A Ross
- Institute for Quantum Matter and Department of Physics and Astronomy, The Johns Hopkins University, Baltimore, Maryland 21218, USA
- NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA
| | - B A Trump
- Department of Chemistry, The Johns Hopkins University, Baltimore, Maryland 21218, USA
| | - T M McQueen
- Institute for Quantum Matter and Department of Physics and Astronomy, The Johns Hopkins University, Baltimore, Maryland 21218, USA
- Department of Chemistry, The Johns Hopkins University, Baltimore, Maryland 21218, USA
- Department of Materials Science and Engineering, The Johns Hopkins University, Baltimore, Maryland 21218, USA
| | - K Kimura
- Institute for Solid State Physics (ISSP), University of Tokyo, Kashiwa, Chiba 277-8581, Japan
- Division of Materials Physics, Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531, Japan
| | - S Nakatsuji
- Institute for Solid State Physics (ISSP), University of Tokyo, Kashiwa, Chiba 277-8581, Japan
- CREST, Japan Science and Technology Agency, Kawaguchi, Saitama 332-0012, Japan
| | - Y Qiu
- NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA
| | - D M Pajerowski
- NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA
| | - J R D Copley
- NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA
| | - C L Broholm
- Institute for Quantum Matter and Department of Physics and Astronomy, The Johns Hopkins University, Baltimore, Maryland 21218, USA
- NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA
- Department of Materials Science and Engineering, The Johns Hopkins University, Baltimore, Maryland 21218, USA
| |
Collapse
|
7
|
Sanders MB, Krizan JW, Plumb KW, McQueen TM, Cava RJ. NaSrMn 2F 7, NaCaFe 2F 7, and NaSrFe 2F 7: novel single crystal pyrochlore antiferromagnets. J Phys Condens Matter 2017; 29:045801. [PMID: 27875333 DOI: 10.1088/1361-648x/29/4/045801] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
The crystal structures and magnetic properties of three previously unreported A2B2F7 pyrochlore materials, NaSrMn2F7, NaCaFe2F7, and NaSrFe2F7 are presented. In these compounds, either S = 2Fe2+ or S = 5/2Mn2+ is on the B site, while nonmagnetic Na and Ca (Na and Sr) are disordered on the A site. The materials, which were grown as crystals via the floating zone method, display high effective magnetic moments and large Curie-Weiss thetas. Despite these characteristics, no ordering transition is detected. However, freezing of the magnetic spins, characterized by peaks in the susceptibility or specific heat, is observed at very low temperatures. The empirical frustration index, f = -θ CW/T f, for the materials are 36 (NaSrMn2F7), 27 (NaSrFe2F7), and 19 (NaCaFe2F7). AC susceptibility, DC susceptibility, and heat capacity measurements are used to characterize the observed spin glass behavior. The results suggest that the compounds are frustrated pyrochlore antiferromagnets with weak bond disorder. The magnetic phenomena that these fluoride pyrochlores exhibit, in addition to their availability as relatively large single crystals, make them promising candidates for the study of geometric magnetic frustration.
Collapse
Affiliation(s)
- M B Sanders
- Department of Chemistry, Princeton University, Princeton, NJ 08544, USA
| | | | | | | | | |
Collapse
|
8
|
Fry-Petit AM, Rebola AF, Mourigal M, Valentine M, Drichko N, Sheckelton JP, Fennie CJ, McQueen TM. Direct assignment of molecular vibrations via normal mode analysis of the neutron dynamic pair distribution function technique. J Chem Phys 2015; 143:124201. [PMID: 26429001 DOI: 10.1063/1.4930607] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
For over a century, vibrational spectroscopy has enhanced the study of materials. Yet, assignment of particular molecular motions to vibrational excitations has relied on indirect methods. Here, we demonstrate that applying group theoretical methods to the dynamic pair distribution function analysis of neutron scattering data provides direct access to the individual atomic displacements responsible for these excitations. Applied to the molecule-based frustrated magnet with a potential magnetic valence-bond state, LiZn2Mo3O8, this approach allows direct assignment of the constrained rotational mode of Mo3O13 clusters and internal modes of MoO6 polyhedra. We anticipate that coupling this well known data analysis technique with dynamic pair distribution function analysis will have broad application in connecting structural dynamics to physical properties in a wide range of molecular and solid state systems.
Collapse
Affiliation(s)
- A M Fry-Petit
- Department of Chemistry, The Johns Hopkins University, Baltimore, Maryland 21218, USA
| | - A F Rebola
- Department of Applied Physics, Cornell University, Ithaca, New York 14853, USA
| | - M Mourigal
- Institute for Quantum Matter and Department of Physics and Astronomy, The Johns Hopkins University, Baltimore, Maryland 21218, USA
| | - M Valentine
- Institute for Quantum Matter and Department of Physics and Astronomy, The Johns Hopkins University, Baltimore, Maryland 21218, USA
| | - N Drichko
- Institute for Quantum Matter and Department of Physics and Astronomy, The Johns Hopkins University, Baltimore, Maryland 21218, USA
| | - J P Sheckelton
- Department of Chemistry, The Johns Hopkins University, Baltimore, Maryland 21218, USA
| | - C J Fennie
- Department of Applied Physics, Cornell University, Ithaca, New York 14853, USA
| | - T M McQueen
- Department of Chemistry, The Johns Hopkins University, Baltimore, Maryland 21218, USA
| |
Collapse
|
9
|
Mourigal M, Wu S, Stone MB, Neilson JR, Caron JM, McQueen TM, Broholm CL. Block Magnetic Excitations in the Orbitally Selective Mott Insulator BaFe_{2}Se_{3}. Phys Rev Lett 2015; 115:047401. [PMID: 26252707 DOI: 10.1103/physrevlett.115.047401] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/12/2014] [Indexed: 06/04/2023]
Abstract
Iron pnictides and selenides display a variety of unusual magnetic phases originating from the interplay between electronic, orbital, and lattice degrees of freedom. Using powder inelastic neutron scattering on the two-leg ladder BaFe_{2}Se_{3}, we fully characterize the static and dynamic spin correlations associated with the Fe_{4} block state, an exotic magnetic ground state observed in this low-dimensional magnet and in Rb_{0.89}Fe_{1.58}Se_{2}. All the magnetic excitations of the Fe_{4} block state predicted by an effective Heisenberg model with localized spins are observed below 300 meV and quantitatively reproduced. However, the data only account for 16(3)μ_{B}^{2} per Fe^{2+}, approximatively 2/3 of the total spectral weight expected for localized S=2 moments. Our results highlight how orbital degrees of freedom in iron-based magnets can conspire to stabilize an exotic magnetic state.
Collapse
Affiliation(s)
- M Mourigal
- Institute for Quantum Matter and Department of Physics and Astronomy, Johns Hopkins University, Baltimore, Maryland 21218, USA
| | - Shan Wu
- Institute for Quantum Matter and Department of Physics and Astronomy, Johns Hopkins University, Baltimore, Maryland 21218, USA
| | - M B Stone
- Quantum Condensed Matter Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - J R Neilson
- Institute for Quantum Matter and Department of Physics and Astronomy, Johns Hopkins University, Baltimore, Maryland 21218, USA
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, USA
| | - J M Caron
- Institute for Quantum Matter and Department of Physics and Astronomy, Johns Hopkins University, Baltimore, Maryland 21218, USA
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, USA
| | - T M McQueen
- Institute for Quantum Matter and Department of Physics and Astronomy, Johns Hopkins University, Baltimore, Maryland 21218, USA
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, USA
- Department of Materials Science and Engineering, Johns Hopkins University, Baltimore, Maryland 21218, USA
| | - C L Broholm
- Institute for Quantum Matter and Department of Physics and Astronomy, Johns Hopkins University, Baltimore, Maryland 21218, USA
- Quantum Condensed Matter Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
- Department of Materials Science and Engineering, Johns Hopkins University, Baltimore, Maryland 21218, USA
| |
Collapse
|
10
|
Fuhrman WT, Leiner J, Nikolić P, Granroth GE, Stone MB, Lumsden MD, DeBeer-Schmitt L, Alekseev PA, Mignot JM, Koohpayeh SM, Cottingham P, Phelan WA, Schoop L, McQueen TM, Broholm C. Interaction driven subgap spin exciton in the Kondo insulator SmB6. Phys Rev Lett 2015; 114:036401. [PMID: 25659009 DOI: 10.1103/physrevlett.114.036401] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/11/2014] [Indexed: 06/04/2023]
Abstract
Using inelastic neutron scattering, we map a 14 meV coherent resonant mode in the topological Kondo insulator SmB6 and describe its relation to the low energy insulating band structure. The resonant intensity is confined to the X and R high symmetry points, repeating outside the first Brillouin zone and dispersing less than 2 meV, with a 5d-like magnetic form factor. We present a slave-boson treatment of the Anderson Hamiltonian with a third neighbor dominated hybridized band structure. This approach produces a spin exciton below the charge gap with features that are consistent with the observed neutron scattering. We find that maxima in the wave vector dependence of the inelastic neutron scattering indicate band inversion.
Collapse
Affiliation(s)
- W T Fuhrman
- Institute for Quantum Matter and Department of Physics and Astronomy, The Johns Hopkins University, Baltimore, Maryland 21218, USA
| | - J Leiner
- Quantum Condensed Matter Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - P Nikolić
- Institute for Quantum Matter and Department of Physics and Astronomy, The Johns Hopkins University, Baltimore, Maryland 21218, USA and School of Physics, Astronomy and Computational Sciences, George Mason University, Fairfax, Virginia 22030, USA
| | - G E Granroth
- Neutron Data Analysis and Visualization Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - M B Stone
- Quantum Condensed Matter Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - M D Lumsden
- Quantum Condensed Matter Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - L DeBeer-Schmitt
- Instrument Source Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - P A Alekseev
- National Research Centre "Kurchatov Institute," 123182 Moscow, Russia and National Research Nuclear University "MEPhI," 115409 Moscow, Russia
| | - J-M Mignot
- Laboratoire Léon Brillouin, CEA-CNRS, CEA/Saclay, 91191 Gif sur Yvette, France
| | - S M Koohpayeh
- Institute for Quantum Matter and Department of Physics and Astronomy, The Johns Hopkins University, Baltimore, Maryland 21218, USA
| | - P Cottingham
- Institute for Quantum Matter and Department of Physics and Astronomy, The Johns Hopkins University, Baltimore, Maryland 21218, USA and Department of Chemistry, The Johns Hopkins University, Baltimore, Maryland 21218, USA
| | - W Adam Phelan
- Institute for Quantum Matter and Department of Physics and Astronomy, The Johns Hopkins University, Baltimore, Maryland 21218, USA and Department of Chemistry, The Johns Hopkins University, Baltimore, Maryland 21218, USA
| | - L Schoop
- Institute for Quantum Matter and Department of Physics and Astronomy, The Johns Hopkins University, Baltimore, Maryland 21218, USA and Department of Chemistry, Princeton University, Princeton, New Jersey 08540, USA
| | - T M McQueen
- Institute for Quantum Matter and Department of Physics and Astronomy, The Johns Hopkins University, Baltimore, Maryland 21218, USA and Department of Chemistry, The Johns Hopkins University, Baltimore, Maryland 21218, USA and Department of Materials Science and Engineering, The Johns Hopkins University, Baltimore, Maryland 21218, USA
| | - C Broholm
- Institute for Quantum Matter and Department of Physics and Astronomy, The Johns Hopkins University, Baltimore, Maryland 21218, USA and Quantum Condensed Matter Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA and Department of Materials Science and Engineering, The Johns Hopkins University, Baltimore, Maryland 21218, USA
| |
Collapse
|
11
|
Morris CM, Valdés Aguilar R, Ghosh A, Koohpayeh SM, Krizan J, Cava RJ, Tchernyshyov O, McQueen TM, Armitage NP. Hierarchy of bound states in the one-dimensional ferromagnetic Ising chain CoNb2O6 investigated by high-resolution time-domain terahertz spectroscopy. Phys Rev Lett 2014; 112:137403. [PMID: 24745454 DOI: 10.1103/physrevlett.112.137403] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/03/2013] [Indexed: 06/03/2023]
Abstract
Kink bound states in the one-dimensional ferromagnetic Ising chain compound CoNb2O6 have been studied using high-resolution time-domain terahertz spectroscopy in zero applied magnetic field. When magnetic order develops at low temperature, nine bound states of kinks become visible. Their energies can be modeled exceedingly well by the Airy function solutions to a 1D Schrödinger equation with a linear confining potential. This sequence of bound states terminates at a threshold energy near 2 times the energy of the lowest bound state. Above this energy scale we observe a broad feature consistent with the onset of the two particle continuum. At energies just below this threshold we observe a prominent excitation that we interpret as a novel bound state of bound states--two pairs of kinks on neighboring chains.
Collapse
Affiliation(s)
- C M Morris
- The Institute for Quantum Matter, Department of Physics and Astronomy, The Johns Hopkins University, Baltimore, Maryland 21218, USA
| | - R Valdés Aguilar
- The Institute for Quantum Matter, Department of Physics and Astronomy, The Johns Hopkins University, Baltimore, Maryland 21218, USA and Center for Integrated Nanotechnologies, Los Alamos National Laboratory. MS K771. Los Alamos, New Mexico 87545, USA
| | - A Ghosh
- The Institute for Quantum Matter, Department of Physics and Astronomy, The Johns Hopkins University, Baltimore, Maryland 21218, USA
| | - S M Koohpayeh
- The Institute for Quantum Matter, Department of Physics and Astronomy, The Johns Hopkins University, Baltimore, Maryland 21218, USA
| | - J Krizan
- Department of Chemistry, Princeton University, Princeton, New Jersey 08544, USA
| | - R J Cava
- Department of Chemistry, Princeton University, Princeton, New Jersey 08544, USA
| | - O Tchernyshyov
- The Institute for Quantum Matter, Department of Physics and Astronomy, The Johns Hopkins University, Baltimore, Maryland 21218, USA
| | - T M McQueen
- The Institute for Quantum Matter, Department of Physics and Astronomy, The Johns Hopkins University, Baltimore, Maryland 21218, USA and Department of Chemistry, The Johns Hopkins University, Baltimore, Maryland 21218, USA
| | - N P Armitage
- The Institute for Quantum Matter, Department of Physics and Astronomy, The Johns Hopkins University, Baltimore, Maryland 21218, USA
| |
Collapse
|
12
|
Mourigal M, Fuhrman WT, Sheckelton JP, Wartelle A, Rodriguez-Rivera JA, Abernathy DL, McQueen TM, Broholm CL. Molecular quantum magnetism in LiZn2Mo3O8. Phys Rev Lett 2014; 112:027202. [PMID: 24484043 DOI: 10.1103/physrevlett.112.027202] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/30/2013] [Indexed: 06/03/2023]
Abstract
Inelastic neutron scattering at low temperatures T≤30 K from a powder of LiZn2Mo3O8 demonstrates this triangular-lattice antiferromagnet hosts collective magnetic excitations from spin-1/2 Mo3O13 molecules. Apparently gapless (Δ<0.2 meV) and extending at least up to 2.5 meV, the low-energy magnetic scattering cross section is surprisingly broad in momentum space and involves one-third of the spins present above 100 K. The data are compatible with the presence of valence bonds involving nearest-neighbor and next-nearest-neighbor spins forming a disordered or dynamic state.
Collapse
Affiliation(s)
- M Mourigal
- Institute for Quantum Matter and Department of Physics and Astronomy, Johns Hopkins University, Baltimore, Maryland 21218, USA
| | - W T Fuhrman
- Institute for Quantum Matter and Department of Physics and Astronomy, Johns Hopkins University, Baltimore, Maryland 21218, USA
| | - J P Sheckelton
- Institute for Quantum Matter and Department of Physics and Astronomy, Johns Hopkins University, Baltimore, Maryland 21218, USA and Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, USA
| | - A Wartelle
- Institute for Quantum Matter and Department of Physics and Astronomy, Johns Hopkins University, Baltimore, Maryland 21218, USA and École Normale Supérieure de Lyon, Université de Lyon, 46 Allée d'Italie, 69364 Lyon Cedex 07, France
| | - J A Rodriguez-Rivera
- NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA and Department of Materials Science and Engineering, University of Maryland, College Park, Maryland 20742, USA
| | - D L Abernathy
- Quantum Condensed Matter Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6475, USA
| | - T M McQueen
- Institute for Quantum Matter and Department of Physics and Astronomy, Johns Hopkins University, Baltimore, Maryland 21218, USA and Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, USA
| | - C L Broholm
- Institute for Quantum Matter and Department of Physics and Astronomy, Johns Hopkins University, Baltimore, Maryland 21218, USA and NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA and Quantum Condensed Matter Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6475, USA
| |
Collapse
|
13
|
Arpino KE, Wallace DC, Nie YF, Birol T, King PDC, Chatterjee S, Uchida M, Koohpayeh SM, Wen JJ, Page K, Fennie CJ, Shen KM, McQueen TM. Evidence for topologically protected surface states and a superconducting phase in [Tl4](Tl(1-x)Sn(x))Te3 using photoemission, specific heat, and magnetization measurements, and density functional theory. Phys Rev Lett 2014; 112:017002. [PMID: 24483920 DOI: 10.1103/physrevlett.112.017002] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/19/2013] [Indexed: 05/22/2023]
Abstract
We report the discovery of surface states in the perovskite superconductor [Tl4]TlTe3 (Tl5Te3) and its nonsuperconducting tin-doped derivative [Tl4](Tl0.4Sn0.6)Te3 as observed by angle-resolved photoemission spectroscopy. Density functional theory calculations predict that the surface states are protected by a Z2 topology of the bulk band structure. Specific heat and magnetization measurements show that Tl5Te3 has a superconducting volume fraction in excess of 95%. Thus Tl5Te3 is an ideal material in which to study the interplay of bulk band topology and superconductivity.
Collapse
Affiliation(s)
- K E Arpino
- Department of Chemistry, The Johns Hopkins University, Baltimore, Maryland 21218, USA and Institute for Quantum Matter, Department of Physics and Astronomy, The Johns Hopkins University, Baltimore, Maryland 21218, USA
| | - D C Wallace
- Department of Chemistry, The Johns Hopkins University, Baltimore, Maryland 21218, USA and Institute for Quantum Matter, Department of Physics and Astronomy, The Johns Hopkins University, Baltimore, Maryland 21218, USA
| | - Y F Nie
- Department of Physics, Laboratory of Atomic and Solid State Physics, Cornell University, Ithaca, New York 14853, USA and Department of Materials Science and Engineering, Cornell University, Ithaca, New York 14853, USA
| | - T Birol
- School of Applied and Engineering Physics, Cornell University, Ithaca, New York 14853, USA
| | - P D C King
- Department of Physics, Laboratory of Atomic and Solid State Physics, Cornell University, Ithaca, New York 14853, USA and Kavli Institute at Cornell for Nanoscale Science, Cornell University, Ithaca, New York 14853, USA
| | - S Chatterjee
- Department of Physics, Laboratory of Atomic and Solid State Physics, Cornell University, Ithaca, New York 14853, USA
| | - M Uchida
- Department of Physics, Laboratory of Atomic and Solid State Physics, Cornell University, Ithaca, New York 14853, USA
| | - S M Koohpayeh
- Institute for Quantum Matter, Department of Physics and Astronomy, The Johns Hopkins University, Baltimore, Maryland 21218, USA
| | - J-J Wen
- Institute for Quantum Matter, Department of Physics and Astronomy, The Johns Hopkins University, Baltimore, Maryland 21218, USA
| | - K Page
- Lujan Neutron Scattering Center, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
| | - C J Fennie
- School of Applied and Engineering Physics, Cornell University, Ithaca, New York 14853, USA
| | - K M Shen
- Department of Physics, Laboratory of Atomic and Solid State Physics, Cornell University, Ithaca, New York 14853, USA and Kavli Institute at Cornell for Nanoscale Science, Cornell University, Ithaca, New York 14853, USA
| | - T M McQueen
- Department of Chemistry, The Johns Hopkins University, Baltimore, Maryland 21218, USA and Institute for Quantum Matter, Department of Physics and Astronomy, The Johns Hopkins University, Baltimore, Maryland 21218, USA
| |
Collapse
|
14
|
Sheckelton JP, Neilson JR, Soltan DG, McQueen TM. Possible valence-bond condensation in the frustrated cluster magnet LiZn2Mo3O8. Nat Mater 2012; 11:493-496. [PMID: 22561902 DOI: 10.1038/nmat3329] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/01/2011] [Accepted: 04/04/2012] [Indexed: 05/31/2023]
Abstract
The emergence of complex electronic behaviour from simple ingredients has resulted in the discovery of numerous states of matter. Many examples are found in systems exhibiting geometric magnetic frustration, which prevents simultaneous satisfaction of all magnetic interactions. This frustration gives rise to complex magnetic properties such as chiral spin structures, orbitally driven magnetism, spin-ice behaviour exhibiting Dirac strings with magnetic monopoles, valence-bond solids and spin liquids. Here we report the synthesis and characterization of LiZn(2)Mo(3)O(8), a geometrically frustrated antiferromagnet in which the magnetic moments are localized on small transition-metal clusters rather than individual ions. By doing so, first-order Jahn-Teller instabilities and orbital ordering are prevented, allowing the strongly interacting magnetic clusters in LiZn(2)Mo(3)O(8) to probably give rise to an exotic condensed valence-bond ground state reminiscent of the proposed resonating valence-bond state. Our results also link magnetism on clusters to geometric magnetic frustration in extended solids, demonstrating a new approach for unparalleled chemical control and tunability in the search for collective, emergent electronic states of matter.
Collapse
|
15
|
Medvedev S, McQueen TM, Troyan IA, Palasyuk T, Eremets MI, Cava RJ, Naghavi S, Casper F, Ksenofontov V, Wortmann G, Felser C. Electronic and magnetic phase diagram of beta-Fe(1.01)Se with superconductivity at 36.7 K under pressure. Nat Mater 2009; 8:630-633. [PMID: 19525948 DOI: 10.1038/nmat2491] [Citation(s) in RCA: 217] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/13/2009] [Accepted: 05/29/2009] [Indexed: 05/25/2023]
Abstract
The discovery of new high-temperature superconductors based on FeAs has led to a new 'gold rush' in high-T(C) superconductivity. All of the new superconductors share the same common structural motif of FeAs layers and reach T(C) values up to 55 K (ref. 2). Recently, superconductivity has been reported in FeSe (ref. 3), which has the same iron pnictide layer structure, but without separating layers. Here, we report the magnetic and electronic phase diagram of beta-Fe(1.01)Se as a function of temperature and pressure. The superconducting transition temperature increases from 8.5 to 36.7 K under an applied pressure of 8.9 GPa. It then decreases at higher pressures. A marked change in volume is observed at the same time as T(C) rises, owing to a collapse of the separation between the Fe(2)Se(2) layers. No static magnetic ordering is observed for the whole p-T phase diagram. We also report that at higher pressures (starting around 7 GPa and completed at 38 GPa), Fe(1.01)Se transforms to a hexagonal NiAs-type structure and exhibits non-magnetic behaviour.
Collapse
Affiliation(s)
- S Medvedev
- Institut für Anorganische und Analytische Chemie, University Mainz, 55099 Mainz, Germany
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
16
|
McQueen TM, Williams AJ, Stephens PW, Tao J, Zhu Y, Ksenofontov V, Casper F, Felser C, Cava RJ. Tetragonal-to-orthorhombic structural phase transition at 90 K in the superconductor Fe(1.01)Se. Phys Rev Lett 2009; 103:057002. [PMID: 19792526 DOI: 10.1103/physrevlett.103.057002] [Citation(s) in RCA: 118] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/07/2009] [Indexed: 05/25/2023]
Abstract
In this Letter we show that superconducting Fe(1.01)Se undergoes a structural transition at 90 K from a tetragonal to an orthorhombic phase but that nonsuperconducting Fe(1.03)Se does not. High resolution electron microscopy at low temperatures further reveals an unexpected additional modulation of the crystal structure of the superconducting phase that involves displacements of the Fe atoms, and that the nonsuperconducting composition shows a different, complex nanometer-scale structural modulation. Finally, we show that magnetism is not the driving force for the phase transition in the superconducting phase.
Collapse
Affiliation(s)
- T M McQueen
- Department of Chemistry, Princeton University, Princeton New Jersey 08544, USA
| | | | | | | | | | | | | | | | | |
Collapse
|
17
|
Abstract
Iron selenide, Fe(1.01)Se, the layered parent compound of the recently discovered superconducting arsenide family, has previously been shown to be non-magnetic and superconducting with a critical temperature of 8 K. Here we show that copper can be substituted at the iron site in Fe(1.01)Se up to a solubility limit of 20-30%, after which a first-order transition to the three-dimensional CuFeSe(2) structure type is observed. As little as 1.5% copper is sufficient to suppress the superconductivity, and 4% drives the system through a metal-insulator transition. A local magnetic moment is introduced, which maximizes near 12% doping, where a spin-glass transition near 15 K is observed.
Collapse
Affiliation(s)
- A J Williams
- Department of Chemistry, Princeton University, Princeton, NJ 08544, USA
| | | | | | | | | |
Collapse
|
18
|
Imai T, Ahilan K, Ning FL, McQueen TM, Cava RJ. Why does undoped FeSe become a high-Tc superconductor under pressure? Phys Rev Lett 2009; 102:177005. [PMID: 19518818 DOI: 10.1103/physrevlett.102.177005] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/22/2009] [Indexed: 05/27/2023]
Abstract
Unlike the parent phases of the iron-arsenide high-Tc superconductors, undoped FeSe is not magnetically ordered and exhibits superconductivity with Tc approximately 9 K. Equally surprising is the fact that applied pressure dramatically enhances the modest Tc to approximately 37 K. We investigate the electronic properties of FeSe using 77Se NMR to search for the key to the superconducting mechanism. We demonstrate that the electronic properties of FeSe are very similar to those of electron-doped FeAs superconductors, and that antiferromagnetic spin fluctuations are strongly enhanced near Tc. Furthermore, applied pressure enhances spin fluctuations. Our findings suggest a link between spin fluctuations and the superconducting mechanism in FeSe.
Collapse
Affiliation(s)
- T Imai
- Department of Physics and Astronomy, McMaster University, Hamilton, Ontario L8S4M1, Canada
| | | | | | | | | |
Collapse
|
19
|
Klimczuk T, Zandbergen HW, Huang Q, McQueen TM, Ronning F, Kusz B, Thompson JD, Cava RJ. Cluster-glass behavior of a highly oxygen deficient perovskite, BaBi(0.28)Co(0.72)O(2.2). J Phys Condens Matter 2009; 21:105801. [PMID: 21817439 DOI: 10.1088/0953-8984/21/10/105801] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
A highly oxygen deficient perovskite, BaBi(0.28)Co(0.72)O(2.2), was synthesized by solid state reaction. The crystal structure was determined by means of neutron and x-ray powder diffraction. The material exhibits semiconducting behavior with an energy gap of 1.8 eV. The electron diffraction study does not reveal long range Bi:Co ordering; instead it shows the existence of short range ordering in this phase. The AC and DC magnetic susceptibility studies reveal cluster-glass behavior, which has its origin in the interacting ferromagnetic clusters present.
Collapse
Affiliation(s)
- T Klimczuk
- Los Alamos National Laboratory, Los Alamos, NM 87545, USA. Department of Chemistry, Princeton University, Princeton, NJ 08544, USA
| | | | | | | | | | | | | | | |
Collapse
|
20
|
McQueen TM, Stephens PW, Huang Q, Klimczuk T, Ronning F, Cava RJ. Successive orbital ordering transitions in NaVO2. Phys Rev Lett 2008; 101:166402. [PMID: 18999690 DOI: 10.1103/physrevlett.101.166402] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/02/2008] [Indexed: 05/27/2023]
Abstract
Physical property measurements on samples of triangular-lattice NaVO2 reveal two successive orbital ordering transitions. At 300 K, the structure is rhombohedral. At 98 K, the system undergoes a second-order transition to a monoclinic phase in which the in-plane V-V distances separate into four short and two long bonds, corresponding to orbital ordering of one electron per V3+. Below 93 K, there is a first-order transition to a second monoclinic phase with four long and two short V-V bonds, consistent with orbital ordering of two electrons per V3+. Long range magnetic ordering of 0.98(2)mu_(B) per V3+ (3d(2)) sets in at the 93 K structural transition. The orbital ordering relieves the geometric frustration and leads to a magnetically ordered ground state.
Collapse
Affiliation(s)
- T M McQueen
- Department of Chemistry, Princeton University, Princeton, NJ 08544, USA
| | | | | | | | | | | |
Collapse
|
21
|
McQueen TM, West DV, Muegge B, Huang Q, Noble K, Zandbergen HW, Cava RJ. Frustrated ferroelectricity in niobate pyrochlores. J Phys Condens Matter 2008; 20:235210. [PMID: 21694301 DOI: 10.1088/0953-8984/20/23/235210] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
The crystal structures of the A(2)B(2)O(7-x) niobium based pyrochlores Y(2)(Nb(0.86)Y(0.14))(2)O(6.91), CaYNb(2)O(7), and Y(2)NbTiO(7) are reported, determined by means of powder neutron diffraction. These compounds represent the first observation of B-site displacements in the pyrochlore structure: the B-site ions are found to be displaced from the ideal pyrochlore positions, creating electric dipoles. The orientations of these dipoles are fully analogous to orientations of the magnetic moments in Ising spin based magnetically frustrated pyrochlores. Diffuse scattering in electron diffraction patterns shows that the displacements are only short range ordered, indicative of geometric frustration of the collective dielectric state of the materials. Comparison to the crystal structure of the Nb(5+) (d(0)) pyrochlore La(2)ScNbO(7) supports the prediction that charge singlets, driven by the tendency of Nb to form metal-metal bonds, are present in these pyrochlores. The observed lack of long range order to these singlets suggests that Nb(4+) based pyrochlores represent the dielectric analogy to the geometric frustration of magnetic moments observed in rare earth pyrochlores.
Collapse
Affiliation(s)
- T M McQueen
- Department of Chemistry, Princeton University, Princeton, NJ 08544, USA
| | | | | | | | | | | | | |
Collapse
|