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Alcón I, Ribas-Ariño J, Moreira IDPR, Bromley ST. Emergent Spin Frustration in Neutral Mixed-Valence 2D Conjugated Polymers: A Potential Quantum Materials Platform. J Am Chem Soc 2023; 145:5674-5683. [PMID: 36877195 PMCID: PMC10021012 DOI: 10.1021/jacs.2c11185] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/07/2023]
Abstract
Two-dimensional conjugated polymers (2DCPs)─organic 2D materials composed of arrays of carbon sp2 centers connected by π-conjugated linkers─are attracting increasing attention due to their potential applications in device technologies. This interest stems from the ability of 2DCPs to host a range of correlated electronic and magnetic states (e.g., Mott insulators). Substitution of all carbon sp2 centers in 2DCPs by nitrogen or boron results in diamagnetic insulating states. Partial substitution of C sp2 centers by B or N atoms has not yet been considered for extended 2DCPs but has been extensively studied in the analogous neutral mixed-valence molecular systems. Here, we employ accurate first-principles calculations to predict the electronic and magnetic properties of a new class of hexagonally connected neutral mixed-valence 2DCPs in which every other C sp2 nodal center is substituted by either a N or B atom. We show that these neutral mixed-valence 2DCPs significantly energetically favor a state with emergent superexchange-mediated antiferromagnetic (AFM) interactions between C-based spin-1/2 centers on a triangular sublattice. These AFM interactions are surprisingly strong and comparable to those in the parent compounds of cuprate superconductors. The rigid and covalently linked symmetric triangular AFM lattice in these materials thus provides a highly promising and robust basis for 2D spin frustration. As such, extended mixed-valence 2DCPs are a highly attractive platform for the future bottom-up realization of a new class of all-organic quantum materials, which could host exotic correlated electronic states (e.g., unusual magnetic ordering, quantum spin liquids).
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Affiliation(s)
- Isaac Alcón
- Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC and BIST, Campus UAB, Bellaterra, 08193 Barcelona, Spain
| | - Jordi Ribas-Ariño
- Departament de Ciència de Materials i Química Física & Institut de Química Teòrica i Computacional (IQTC), Universitat de Barcelona, c/ Martí i Franquès 1-11, 08028 Barcelona, Spain
| | - Ibério de P R Moreira
- Departament de Ciència de Materials i Química Física & Institut de Química Teòrica i Computacional (IQTC), Universitat de Barcelona, c/ Martí i Franquès 1-11, 08028 Barcelona, Spain
| | - Stefan T Bromley
- Departament de Ciència de Materials i Química Física & Institut de Química Teòrica i Computacional (IQTC), Universitat de Barcelona, c/ Martí i Franquès 1-11, 08028 Barcelona, Spain.,Institució Catalana de Recerca i Estudis Avançats (ICREA), Passeig Lluís Companys 23, 08010 Barcelona, Spain
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2
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Unconventional short-range structural fluctuations in cuprate superconductors. Sci Rep 2022; 12:20483. [DOI: 10.1038/s41598-022-22150-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2022] [Accepted: 10/10/2022] [Indexed: 11/29/2022] Open
Abstract
AbstractThe interplay between structural and electronic degrees of freedom in complex materials is the subject of extensive debate in physics and materials science. Particularly interesting questions pertain to the nature and extent of pre-transitional short-range order in diverse systems ranging from shape-memory alloys to unconventional superconductors, and how this microstructure affects macroscopic properties. Here we use neutron and X-ray diffuse scattering to uncover universal structural fluctuations in La2-xSrxCuO4 and Tl2Ba2CuO6+δ, two cuprate superconductors with distinct point disorder effects and with optimal superconducting transition temperatures that differ by more than a factor of two. The fluctuations are present in wide doping and temperature ranges, including compositions that maintain high average structural symmetry, and they exhibit unusual, yet simple scaling behaviour. The scaling regime is robust and universal, similar to the well-known critical fluctuations close to second-order phase transitions, but with a distinctly different physical origin. We relate this behaviour to pre-transitional phenomena in a broad class of systems with structural and magnetic transitions, and propose an explanation based on rare structural fluctuations caused by intrinsic nanoscale inhomogeneity. We also uncover parallels with superconducting fluctuations, which indicates that the underlying inhomogeneity plays an important role in cuprate physics.
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3
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Horsley E, Rao X, Yi SB, Kim YJ. Magnetic dilution of a honeycomb lattice XY magnet CoTiO 3. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2022; 34:135803. [PMID: 34986470 DOI: 10.1088/1361-648x/ac484c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/01/2021] [Accepted: 01/05/2022] [Indexed: 06/14/2023]
Abstract
We report our study of cobalt (II) titanate, CoTiO3, in which magnetic Co ions are replaced by non-magnetic ions. The antiferromagnetic ordering transition of CoTiO3around 37 K is described with ferromagnetic honeycomb layers coupled antiferromagnetically along the crystallographicc-direction. The effect of magnetic dilution on the Néel temperature of this material is investigated through the doping of Zn2+and Mg2+in place of Co2+for various dilution levels up tox+y= 0.46 in Co1-x-yZnxMgyTiO3. Single phase polycrystalline samples have been synthesized and their structural and magnetic properties have been examined. A linear relation between dilution and the Néel temperature is observed over a wide doping range. A linear extrapolation would suggest that the required dilution level to suppress magnetic order is aroundx+y∼ 0.74, well beyond the classical percolation threshold. The implication of this observation for microscopic models for describing CoTiO3is discussed.
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Affiliation(s)
- Ezekiel Horsley
- Department of Physics, University of Toronto, Toronto, ON M5S 1A7, Canada
| | - Xin Rao
- Hefei National Laboratory for Physical Sciences at Microscale, Department of Physics, and Key Laboratory of Strongly-Coupled Quantum Matter Physics (CAS), University of Science and Technology of China, Hefei, Anhui 230026, People's Republic of China
| | - Sang Bum Yi
- Department of Physics, University of Toronto, Toronto, ON M5S 1A7, Canada
| | - Young-June Kim
- Department of Physics, University of Toronto, Toronto, ON M5S 1A7, Canada
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4
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Puphal P, Wu YM, Fürsich K, Lee H, Pakdaman M, Bruin JAN, Nuss J, Suyolcu YE, van Aken PA, Keimer B, Isobe M, Hepting M. Topotactic transformation of single crystals: From perovskite to infinite-layer nickelates. SCIENCE ADVANCES 2021; 7:eabl8091. [PMID: 34860545 PMCID: PMC8641924 DOI: 10.1126/sciadv.abl8091] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Topotactic transformations between related crystal structures are a powerful emerging route for the synthesis of novel quantum materials. Whereas most such “soft chemistry” experiments have been carried out on polycrystalline powders or thin films, the topotactic modification of single crystals, the gold standard for physical property measurements on quantum materials, has been studied only sparsely. Here, we report the topotactic reduction of La1−xCaxNiO3 single crystals to La1−xCaxNiO2+δ using CaH2 as the reducing agent. The transformation from the three-dimensional perovskite to the quasi–two-dimensional infinite-layer phase was thoroughly characterized by x-ray diffraction, electron microscopy, Raman spectroscopy, magnetometry, and electrical transport measurements. Our work demonstrates that the infinite-layer structure can be realized as a bulk phase in crystals with micrometer-sized single domains. The electronic properties of these specimens resemble those of epitaxial thin films rather than powders with similar compositions.
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Affiliation(s)
- Pascal Puphal
- Max Planck Institute for Solid State Research, Heisenbergstraße 1, 70569 Stuttgart, Germany
| | - Yu-Mi Wu
- Max Planck Institute for Solid State Research, Heisenbergstraße 1, 70569 Stuttgart, Germany
| | - Katrin Fürsich
- Max Planck Institute for Solid State Research, Heisenbergstraße 1, 70569 Stuttgart, Germany
| | - Hangoo Lee
- Max Planck Institute for Solid State Research, Heisenbergstraße 1, 70569 Stuttgart, Germany
| | - Mohammad Pakdaman
- Max Planck Institute for Solid State Research, Heisenbergstraße 1, 70569 Stuttgart, Germany
| | - Jan A N Bruin
- Max Planck Institute for Solid State Research, Heisenbergstraße 1, 70569 Stuttgart, Germany
| | - Jürgen Nuss
- Max Planck Institute for Solid State Research, Heisenbergstraße 1, 70569 Stuttgart, Germany
| | - Y Eren Suyolcu
- Department of Materials Science and Engineering, Cornell University, Ithaca, NY 14853, USA
| | - Peter A van Aken
- Max Planck Institute for Solid State Research, Heisenbergstraße 1, 70569 Stuttgart, Germany
| | - Bernhard Keimer
- Max Planck Institute for Solid State Research, Heisenbergstraße 1, 70569 Stuttgart, Germany
| | - Masahiko Isobe
- Max Planck Institute for Solid State Research, Heisenbergstraße 1, 70569 Stuttgart, Germany
| | - Matthias Hepting
- Max Planck Institute for Solid State Research, Heisenbergstraße 1, 70569 Stuttgart, Germany
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5
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Kim HH, Lefrançois E, Kummer K, Fumagalli R, Brookes NB, Betto D, Nakata S, Tortora M, Porras J, Loew T, Barber ME, Braicovich L, Mackenzie AP, Hicks CW, Keimer B, Minola M, Le Tacon M. Charge Density Waves in YBa_{2}Cu_{3}O_{6.67} Probed by Resonant X-Ray Scattering under Uniaxial Compression. PHYSICAL REVIEW LETTERS 2021; 126:037002. [PMID: 33543973 DOI: 10.1103/physrevlett.126.037002] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/19/2020] [Revised: 11/10/2020] [Accepted: 12/14/2020] [Indexed: 06/12/2023]
Abstract
We report a comprehensive Cu L_{3}-edge resonant x-ray scattering (RXS) study of two- and three-dimensional (2D and 3D) incommensurate charge correlations in single crystals of the underdoped high-temperature superconductor YBa_{2}Cu_{3}O_{6.67} under uniaxial compression up to 1% along the two inequivalent Cu─O─Cu bond directions (a and b) in the CuO_{2} planes. We confirm the strong in-plane anisotropy of the 2D charge correlations and observe their symmetric response to pressure: pressure along a enhances correlations along b, and vice versa. Our results imply that the underlying order parameter is uniaxial. In contrast, 3D long-range charge order is only observed along b in response to compression along a. Spectroscopic RXS measurements show that the 3D charge order resides exclusively in the CuO_{2} planes and may thus be generic to the cuprates. We discuss implications of these results for models of electronic nematicity and for the interplay between charge order and superconductivity.
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Affiliation(s)
- H-H Kim
- Max Planck Institute for Solid State Research, Heisenbergstraße 1, D-70569 Stuttgart, Germany
| | - E Lefrançois
- Max Planck Institute for Solid State Research, Heisenbergstraße 1, D-70569 Stuttgart, Germany
| | - K Kummer
- ESRF, The European Synchrotron, 71 Avenue des Martyrs, F-38043 Grenoble, France
| | - R Fumagalli
- Dipartimento di Fisica, Politecnico di Milano, I-20133 Milano, Italy
| | - N B Brookes
- ESRF, The European Synchrotron, 71 Avenue des Martyrs, F-38043 Grenoble, France
| | - D Betto
- Max Planck Institute for Solid State Research, Heisenbergstraße 1, D-70569 Stuttgart, Germany
- ESRF, The European Synchrotron, 71 Avenue des Martyrs, F-38043 Grenoble, France
| | - S Nakata
- Max Planck Institute for Solid State Research, Heisenbergstraße 1, D-70569 Stuttgart, Germany
| | - M Tortora
- Max Planck Institute for Solid State Research, Heisenbergstraße 1, D-70569 Stuttgart, Germany
| | - J Porras
- Max Planck Institute for Solid State Research, Heisenbergstraße 1, D-70569 Stuttgart, Germany
| | - T Loew
- Max Planck Institute for Solid State Research, Heisenbergstraße 1, D-70569 Stuttgart, Germany
| | - M E Barber
- Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Straße 40, D-01187 Dresden, Germany
| | - L Braicovich
- ESRF, The European Synchrotron, 71 Avenue des Martyrs, F-38043 Grenoble, France
- Dipartimento di Fisica, Politecnico di Milano, I-20133 Milano, Italy
| | - A P Mackenzie
- Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Straße 40, D-01187 Dresden, Germany
- Scottish Universities Physics Alliance, School of Physics and Astronomy, University of St Andrews, St Andrews KY16 9SS, United Kingdom
| | - C W Hicks
- Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Straße 40, D-01187 Dresden, Germany
| | - B Keimer
- Max Planck Institute for Solid State Research, Heisenbergstraße 1, D-70569 Stuttgart, Germany
| | - M Minola
- Max Planck Institute for Solid State Research, Heisenbergstraße 1, D-70569 Stuttgart, Germany
| | - M Le Tacon
- Institute for Quantum Materials and Technologies, Karlsruhe Institute of Technology, D-76344 Eggenstein-Leopoldshafen, Germany
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6
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Revelli Beaumont M, Hemme P, Gallais Y, Sacuto A, Jacob K, Valade L, de Caro D, Faulmann C, Cazayous M. Possible observation of the signature of the bad metal phase and its crossover to a Fermi liquid in κ-(BEDT-TTF) 2Cu(NCS) 2 bulk and nanoparticles by Raman scattering. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2021; 33:125403. [PMID: 33463531 DOI: 10.1088/1361-648x/abd813] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
κ-(BEDT-TTF)2Cu(NCS)2 has been investigated by Raman scattering in both bulk and nanoparticle compounds. Phonon modes from 20 to 1600 cm-1 have been assigned. Focusing on the unexplored low frequency phonons, a plateau in frequencies is observed in the bulk phonons between 50 and 100 K and assigned to the signature of the bad metal phase. Nanoparticles of κ-(BEDT-TTF)2Cu(NCS)2 exhibit anomalies at 50 K associated to the crossover from a bad metal to a Fermi liquid whose origins are discussed.
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Affiliation(s)
- M Revelli Beaumont
- Laboratoire Matériaux et Phénomènes Quantiques (UMR 7162 CNRS), Université de Paris, 75205 Paris Cedex 13, France. Laboratoire de Chimie de Coordination (UPR 8241), Université Paul Sabatier Toulouse, France
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7
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Linking the pseudogap in the cuprates with local symmetry breaking: A commentary. Proc Natl Acad Sci U S A 2019; 116:14395-14397. [PMID: 31285324 PMCID: PMC6642401 DOI: 10.1073/pnas.1908786116] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
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8
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Avella A, Oleś AM, Horsch P. Defect-Induced Orbital Polarization and Collapse of Orbital Order in Doped Vanadium Perovskites. PHYSICAL REVIEW LETTERS 2019; 122:127206. [PMID: 30978090 DOI: 10.1103/physrevlett.122.127206] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/16/2018] [Indexed: 06/09/2023]
Abstract
We explore mechanisms of orbital-order decay in the doped Mott insulators R_{1-x}(Sr,Ca)_{x}VO_{3} (R=Pr,Y,La) caused by charged (Sr,Ca) defects. Our unrestricted Hartree-Fock analysis focuses on the combined effect of random charged impurities and associated doped holes up to x=0.5. The study is based on a generalized multiband Hubbard model for the relevant vanadium t_{2g} electrons and includes the long-range (i) Coulomb potentials of defects and (ii) electron-electron interactions. We show that the rotation of t_{2g} orbitals, induced by the electric field of defects, is a very efficient perturbation that largely controls the suppression of orbital order in these compounds. We investigate the inverse participation number spectra and find that electron states remain localized on few sites even in the regime where orbital order is collapsed. From the change of kinetic and superexchange energy, we can conclude that the motion of doped holes, which is the dominant effect for the reduction of magnetic order in high-T_{c} compounds, is of secondary importance here.
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Affiliation(s)
- Adolfo Avella
- Dipartimento di Fisica "E.R. Caianiello," Università degli Studi di Salerno, I-84084 Fisciano (SA), Italy
- CNR-SPIN, UOS di Salerno, I-84084 Fisciano (SA), Italy
- Unità CNISM di Salerno, Università degli Studi di Salerno, I-84084 Fisciano (SA), Italy
| | - Andrzej M Oleś
- Marian Smoluchowski Institute of Physics, Jagiellonian University, Prof. S. Łojasiewicza 11, PL-30348 Kraków, Poland
- Max-Planck-Institut für Festkörperforschung, Heisenbergstrasse 1, D-70569 Stuttgart, Germany
| | - Peter Horsch
- Max-Planck-Institut für Festkörperforschung, Heisenbergstrasse 1, D-70569 Stuttgart, Germany
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9
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Pelc D, Popčević P, Požek M, Greven M, Barišić N. Unusual behavior of cuprates explained by heterogeneous charge localization. SCIENCE ADVANCES 2019; 5:eaau4538. [PMID: 30746450 PMCID: PMC6357730 DOI: 10.1126/sciadv.aau4538] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/12/2018] [Accepted: 12/07/2018] [Indexed: 06/09/2023]
Abstract
The discovery of high-temperature superconductivity in cuprates ranks among the major scientific milestones of the past half century, yet pivotal questions regarding the complex phase diagram of these materials remain unanswered. Generally thought of as doped charge-transfer insulators, these complex oxides exhibit pseudogap, strange-metal, superconducting, and Fermi liquid behavior with increasing hole-dopant concentration. Motivated by recent experimental observations, here we introduce a phenomenological model wherein exactly one hole per planar copper-oxygen unit is delocalized with increasing doping and temperature. The model is percolative in nature, with parameters that are highly consistent with experiments. It comprehensively captures key unconventional experimental results, including the temperature and the doping dependence of the pseudogap phenomenon, the strange-metal linear temperature dependence of the planar resistivity, and the doping dependence of the superfluid density. The success and simplicity of the model greatly demystify the cuprate phase diagram and point to a local superconducting pairing mechanism.
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Affiliation(s)
- D. Pelc
- Department of Physics, Faculty of Science, University of Zagreb, Bijenička cesta 32, HR-10000 Zagreb, Croatia
- School of Physics and Astronomy, University of Minnesota, Minneapolis, MN 55455, USA
| | - P. Popčević
- Institute of Solid State Physics, TU Wien, 1040 Vienna, Austria
- Institute of Physics, HR-10000 Zagreb, Croatia
| | - M. Požek
- Department of Physics, Faculty of Science, University of Zagreb, Bijenička cesta 32, HR-10000 Zagreb, Croatia
| | - M. Greven
- School of Physics and Astronomy, University of Minnesota, Minneapolis, MN 55455, USA
| | - N. Barišić
- Department of Physics, Faculty of Science, University of Zagreb, Bijenička cesta 32, HR-10000 Zagreb, Croatia
- School of Physics and Astronomy, University of Minnesota, Minneapolis, MN 55455, USA
- Institute of Solid State Physics, TU Wien, 1040 Vienna, Austria
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10
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Gabbrielli M, Smerzi A, Pezzè L. Multipartite Entanglement at Finite Temperature. Sci Rep 2018; 8:15663. [PMID: 30353077 PMCID: PMC6199326 DOI: 10.1038/s41598-018-31761-3] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2018] [Accepted: 08/17/2018] [Indexed: 11/10/2022] Open
Abstract
The interplay of quantum and thermal fluctuations in the vicinity of a quantum critical point characterizes the physics of strongly correlated systems. Here we investigate this interplay from a quantum information perspective presenting the universal phase diagram of the quantum Fisher information at a quantum phase transition. Different regions in the diagram are identified by characteristic scaling laws of the quantum Fisher information with respect to temperature. This feature has immediate consequences on the thermal robustness of quantum coherence and multipartite entanglement. We support the theoretical predictions with the analysis of paradigmatic spin systems showing symmetry-breaking quantum phase transitions and free-fermion models characterized by topological phases. In particular we show that topological systems are characterized by the survival of large multipartite entanglement, reaching the Heisenberg limit at finite temperature.
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Affiliation(s)
- Marco Gabbrielli
- QSTAR, INO-CNR and LENS, Largo Enrico Fermi 2, I-50125, Firenze, Italy
| | - Augusto Smerzi
- QSTAR, INO-CNR and LENS, Largo Enrico Fermi 2, I-50125, Firenze, Italy
| | - Luca Pezzè
- QSTAR, INO-CNR and LENS, Largo Enrico Fermi 2, I-50125, Firenze, Italy.
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11
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Li Y, Tabis W, Yu G, Barišić N, Greven M. Hidden Fermi-liquid Charge Transport in the Antiferromagnetic Phase of the Electron-Doped Cuprate Superconductors. PHYSICAL REVIEW LETTERS 2016; 117:197001. [PMID: 27858438 DOI: 10.1103/physrevlett.117.197001] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/17/2016] [Indexed: 06/06/2023]
Abstract
Systematic analysis of the planar resistivity, Hall effect, and cotangent of the Hall angle for the electron-doped cuprates reveals underlying Fermi-liquid behavior even deep in the antiferromagnetic part of the phase diagram. The transport scattering rate exhibits a quadratic temperature dependence, and is nearly independent of doping and compound and carrier type (electrons versus holes), and hence is universal. Our analysis moreover indicates that the material-specific resistivity upturn at low temperatures and low doping has the same origin in both electron- and hole-doped cuprates.
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Affiliation(s)
- Yangmu Li
- School of Physics and Astronomy, University of Minnesota, Minneapolis, Minnesota 55455, USA
| | - W Tabis
- School of Physics and Astronomy, University of Minnesota, Minneapolis, Minnesota 55455, USA
- AGH University of Science and Technology, Faculty of Physics and Applied Computer Science, 30-059 Krakow, Poland
| | - G Yu
- School of Physics and Astronomy, University of Minnesota, Minneapolis, Minnesota 55455, USA
| | - N Barišić
- Fakultät für Physik, Technische Universität Wien, Wiedner Hauptstraße 8, 1040 Wien, Austria
- Department of Physics, Faculty of Science, University of Zagreb, HR-10000 Zagreb, Croatia
| | - M Greven
- School of Physics and Astronomy, University of Minnesota, Minneapolis, Minnesota 55455, USA
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12
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Gretarsson H, Sung NH, Porras J, Bertinshaw J, Dietl C, Bruin JAN, Bangura AF, Kim YK, Dinnebier R, Kim J, Al-Zein A, Moretti Sala M, Krisch M, Le Tacon M, Keimer B, Kim BJ. Persistent Paramagnons Deep in the Metallic Phase of Sr_{2-x}La_{x}IrO_{4}. PHYSICAL REVIEW LETTERS 2016; 117:107001. [PMID: 27636488 DOI: 10.1103/physrevlett.117.107001] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/24/2016] [Indexed: 06/06/2023]
Abstract
We have studied the magnetic excitations of electron-doped Sr_{2-x}La_{x}IrO_{4} (0≤x≤0.10) using resonant inelastic x-ray scattering at the Ir L_{3} edge. The long-range magnetic order is rapidly lost with increasing x, but two-dimensional short-range order (SRO) and dispersive magnon excitations with nearly undiminished spectral weight persist well into the metallic part of the phase diagram. The magnons in the SRO phase are heavily damped and exhibit anisotropic softening. Their dispersions are well described by a pseudospin-1/2 Heisenberg model with exchange interactions whose spatial range increases with doping. We also find a doping-independent high-energy magnetic continuum, which is not described by this model. The spin-orbit excitons arising from the pseudospin-3/2 manifold of the Ir ions broaden substantially in the SRO phase, but remain largely separated from the low-energy magnons. Pseudospin-1/2 models are therefore a good starting point for the theoretical description of the low-energy magnetic dynamics of doped iridates.
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Affiliation(s)
- H Gretarsson
- Max-Planck-Institut für Festkörperforschung, Heisenbergstr. 1, D-70569 Stuttgart, Germany
| | - N H Sung
- Max-Planck-Institut für Festkörperforschung, Heisenbergstr. 1, D-70569 Stuttgart, Germany
| | - J Porras
- Max-Planck-Institut für Festkörperforschung, Heisenbergstr. 1, D-70569 Stuttgart, Germany
| | - J Bertinshaw
- Max-Planck-Institut für Festkörperforschung, Heisenbergstr. 1, D-70569 Stuttgart, Germany
| | - C Dietl
- Max-Planck-Institut für Festkörperforschung, Heisenbergstr. 1, D-70569 Stuttgart, Germany
| | - Jan A N Bruin
- Max-Planck-Institut für Festkörperforschung, Heisenbergstr. 1, D-70569 Stuttgart, Germany
| | - A F Bangura
- Max-Planck-Institut für Festkörperforschung, Heisenbergstr. 1, D-70569 Stuttgart, Germany
| | - Y K Kim
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
- Center for Correlated Electron Systems, Institute for Basic Science, Seoul 151-742, South Korea
- Department of Physics and Astronomy, Seoul National University, Seoul 151-747, South Korea
| | - R Dinnebier
- Max-Planck-Institut für Festkörperforschung, Heisenbergstr. 1, D-70569 Stuttgart, Germany
| | - Jungho Kim
- Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, USA
| | - A Al-Zein
- European Synchrotron Radiation Facility, BP 220, F-38043 Grenoble Cedex, France
| | - M Moretti Sala
- European Synchrotron Radiation Facility, BP 220, F-38043 Grenoble Cedex, France
| | - M Krisch
- European Synchrotron Radiation Facility, BP 220, F-38043 Grenoble Cedex, France
| | - M Le Tacon
- Max-Planck-Institut für Festkörperforschung, Heisenbergstr. 1, D-70569 Stuttgart, Germany
- Karlsruher Institut für Technologie, Institut für Festkörperphysik, Hermann-v.-Helmholtz-Platz 1, D-76344 Eggenstein-Leopoldshafen, Germany
| | - B Keimer
- Max-Planck-Institut für Festkörperforschung, Heisenbergstr. 1, D-70569 Stuttgart, Germany
| | - B J Kim
- Max-Planck-Institut für Festkörperforschung, Heisenbergstr. 1, D-70569 Stuttgart, Germany
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13
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Viskadourakis Z, Sunku SS, Mukherjee S, Andersen BM, Ito T, Sasagawa T, Panagopoulos C. Ferroelectricity in underdoped La-based cuprates. Sci Rep 2015; 5:15268. [PMID: 26486276 PMCID: PMC4614081 DOI: 10.1038/srep15268] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2015] [Accepted: 09/03/2015] [Indexed: 12/02/2022] Open
Abstract
Doping a “parent” antiferromagnetic Mott insulator in cuprates leads to short-range electronic correlations and eventually to high-Tc superconductivity. However, the nature of charge correlations in the lightly doped cuprates remains unclear. Understanding the intermediate electronic phase in the phase diagram (between the parent insulator and the high-Tc superconductor) is expected to elucidate the complexity both inside and outside the superconducting dome, and in particular in the underdoped region. One such phase is ferroelectricity whose origin and relation to the properties of high-Tc superconductors is subject of current research. Here we demonstrate that ferroelectricity and the associated magnetoelectric coupling are in fact common in La-214 cuprates namely, La2-xSrxCuO4, La2LixCu1-xO4 and La2CuO4+x. It is proposed that ferroelectricity may result from local CuO6 octahedral distortions, associated with the dopant atoms and clustering of the doped charge carriers, which break spatial inversion symmetry at the local scale whereas magnetoelectric coupling can be tuned through Dzyaloshinskii-Moriya interaction.
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Affiliation(s)
- Z Viskadourakis
- Crete Center for Quantum Complexity and Nanotechnology, University of Crete, Heraklion 71003, Greece.,IESL-FORTH, Vassilika Vouton, Heraklion 71110, Greece
| | - S S Sunku
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, 637371 Singapore
| | - S Mukherjee
- Niels Bohr Institute, University of Copenhagen, Copenhagen DK-2100, Denmark
| | - B M Andersen
- Niels Bohr Institute, University of Copenhagen, Copenhagen DK-2100, Denmark
| | - T Ito
- National Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaraki 305-8562, Japan
| | - T Sasagawa
- Materials and Structures Laboratory, Tokyo Institute of Technology, Kanagawa 226-8503, Japan
| | - C Panagopoulos
- Crete Center for Quantum Complexity and Nanotechnology, University of Crete, Heraklion 71003, Greece.,Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, 637371 Singapore.,Department of Physics, University of Crete, Heraklion 71003, Greece
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14
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Bramwell ST, Keimer B. Neutron scattering from quantum condensed matter. NATURE MATERIALS 2014; 13:763-767. [PMID: 25191684 DOI: 10.1038/nmat4045] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
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15
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Hayward LE, Hawthorn DG, Melko RG, Sachdev S. Angular fluctuations of a multicomponent order describe the pseudogap of YBa2Cu3O(6+x). Science 2014; 343:1336-9. [PMID: 24653030 DOI: 10.1126/science.1246310] [Citation(s) in RCA: 95] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
The hole-doped cuprate high-temperature superconductors enter the pseudogap regime as their superconducting critical temperature, Tc, falls with decreasing hole density. Recent x-ray scattering experiments in YBa2Cu3O(6+x) observe incommensurate charge-density wave fluctuations whose strength rises gradually over a wide temperature range above Tc, but then decreases as the temperature is lowered below Tc. We propose a theory in which the superconducting and charge-density wave orders exhibit angular fluctuations in a six-dimensional space. The theory provides a natural quantitative fit to the x-ray data and can be a basis for understanding other characteristics of the pseudogap.
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Affiliation(s)
- Lauren E Hayward
- Department of Physics and Astronomy, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada
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16
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Sugai S, Takayanagi Y, Hayamizu N, Muroi T, Shiozaki R, Nohara J, Takenaka K, Okazaki K. Superconducting pairing and the pseudogap in the nematic dynamical stripe phase of La2-xSrxCuO4. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2013; 25:475701. [PMID: 24166932 DOI: 10.1088/0953-8984/25/47/475701] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Fully absorption coefficient corrected Raman spectra were obtained in La2-xSrxCuO4. The B1g spectra have a Fleury-Loudon type two-magnon peak (resonant term) whose energy decreases from 3180 cm(-1) (394 meV) to 440 cm(-1) (55 meV) on increasing the carrier density from x = 0 to 0.25, while the B2g spectra have a 1000-3500 cm(-1) (124-434 meV) hump (hill) whose lower-edge energy increases from x = 0 to 0.115 and then stays constant to x = 0.25. The B2g hump is assigned to the electronic scattering (non-resonant term) of the spectral function with magnetic self-energy. The completely different carrier density dependence arises from anisotropic magnetic excitations of spin-charge stripes. The B1g spectra were assigned to the sum of k ∥ and k⊥ stripe excitations and the B2g spectra to k⊥ stripe excitations according to the calculation by Seibold and Lorenzana (2006 Phys. Rev. B 73 144515). The k ∥ and k⊥ stripe excitations in fluctuating spin-charge stripes were separately detected for the first time. The appearance of only k⊥ stripe excitations in the electronic scattering arises from the charge hopping perpendicular to the stripe. This is the same direction as the Burgers vector of the edge dislocation in metal. The successive charge hopping in the Burgers vector direction across the charge stripes may cause Cooper pairs as predicted by Zaanen et al (2004 Ann. Phys. 310 181). Indeed, this is supported by the experimental fact that the superconducting coherent length coincides with the inter-charge stripe distance in the wide carrier density range. The one-directional charge hopping perpendicular to the stripe causes the flat Fermi surface and the pseudogap near (π,0) and (0,π), but the states around (π/2,π/2) cannot be produced. The low-energy Raman scattering disclosed that the electronic states at the Fermi arc around (π/2,π/2) are coupled to the A1g soft phonon of the tetragonal-orthorhombic phase transition. This suggests that the Fermi arc is produced by the electron-phonon interaction. All the present Raman data suggest that Cooper pairs are formed at moving edge dislocations of dynamical charge stripes.
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Affiliation(s)
- S Sugai
- Department of Physics, Arts and Science, Petroleum Institute, PO Box 2533, Abu Dhabi, UAE. Department of Physics, Faculty of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8602, Japan
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17
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Dean MPM, Dellea G, Springell RS, Yakhou-Harris F, Kummer K, Brookes NB, Liu X, Sun YJ, Strle J, Schmitt T, Braicovich L, Ghiringhelli G, Božović I, Hill JP. Persistence of magnetic excitations in La(2-x)Sr(x)CuO4 from the undoped insulator to the heavily overdoped non-superconducting metal. NATURE MATERIALS 2013; 12:1019-23. [PMID: 23913170 DOI: 10.1038/nmat3723] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/06/2013] [Accepted: 06/26/2013] [Indexed: 05/23/2023]
Abstract
One of the most intensely studied scenarios of high-temperature superconductivity (HTS) postulates pairing by exchange of magnetic excitations. Indeed, such excitations have been observed up to optimal doping in the cuprates. In the heavily overdoped regime, neutron scattering measurements indicate that magnetic excitations have effectively disappeared, and this has been argued to cause the demise of HTS with overdoping. Here we use resonant inelastic X-ray scattering, which is sensitive to complementary parts of reciprocal space, to measure the evolution of the magnetic excitations in La(2-x)Sr(x)CuO4 across the entire phase diagram, from a strongly correlated insulator (x = 0) to a non-superconducting metal (x = 0.40). For x = 0, well-defined magnon excitations are observed. These magnons broaden with doping, but they persist with a similar dispersion and comparable intensity all the way to the non-superconducting, heavily overdoped metallic phase. The destruction of HTS with overdoping is therefore caused neither by the general disappearance nor by the overall softening of magnetic excitations. Other factors, such as the redistribution of spectral weight, must be considered.
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Affiliation(s)
- M P M Dean
- Department of Condensed Matter Physics and Materials Science, Brookhaven National Laboratory, Upton, New York 11973, USA
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18
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Chowdhury D, Swingle B, Berg E, Sachdev S. Singularity of the London penetration depth at quantum critical points in superconductors. PHYSICAL REVIEW LETTERS 2013; 111:157004. [PMID: 24160621 DOI: 10.1103/physrevlett.111.157004] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/21/2013] [Revised: 07/14/2013] [Indexed: 06/02/2023]
Abstract
We present a general theory of the singularity in the London penetration depth at symmetry-breaking and topological quantum critical points within a superconducting phase. While the critical exponents and ratios of amplitudes on the two sides of the transition are universal, an overall sign depends upon the interplay between the critical theory and the underlying Fermi surface. We determine these features for critical points to spin density wave and nematic ordering, and for a topological transition between a superconductor with Z2 fractionalization and a conventional superconductor. We note implications for recent measurements of the London penetration depth in BaFe2(As(1-x)P(x))2 [K. Hashimoto et al., Science 336, 1554 (2012)].
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Affiliation(s)
- Debanjan Chowdhury
- Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA
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19
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Carvalho DC, Plascak JA, Castro LM. Quantum spin-1 anisotropic ferromagnetic Heisenberg model in a crystal field: a variational approach. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2013; 88:032111. [PMID: 24125218 DOI: 10.1103/physreve.88.032111] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/27/2013] [Indexed: 06/02/2023]
Abstract
A variational approach based on Bogoliubov inequality for the free energy is employed in order to treat the quantum spin-1 anisotropic ferromagnetic Heisenberg model in the presence of a crystal field. Within the Bogoliubov scheme an improved pair approximation has been used. The temperature-dependent thermodynamic functions have been obtained and provide much better results than the previous simple mean-field scheme. In one dimension, which is still nonintegrable for quantum spin-1, we get the exact results in the classical limit, or near-exact results in the quantum case, for the free energy, magnetization, and quadrupole moment, as well for the transition temperature. In two and three dimensions the corresponding global phase diagrams have been obtained as a function of the parameters of the Hamiltonian. First-order transition lines, second-order transition lines, tricritical and tetracritical points, and critical endpoints have been located through the analysis of the minimum of the Helmholtz free energy and a Landau-like expansion in the approximated free energy. Only first-order quantum transitions have been found at zero temperature. Limiting cases, such as isotropic Heisenberg, Blume-Capel, and Ising models, have been analyzed and compared to previous results obtained from other analytical approaches as well as from Monte Carlo simulations.
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Affiliation(s)
- D C Carvalho
- Departamento de Física, Instituto de Ciências Exatas, Universidade Federal de Minas Gerais, Caixa Postale 702, 30123-970 Belo Horizonte, Minas Gerais, Brazil
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20
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Ishida S, Nakajima M, Liang T, Kihou K, Lee CH, Iyo A, Eisaki H, Kakeshita T, Tomioka Y, Ito T, Uchida SI. Effect of Doping on the Magnetostructural Ordered Phase of Iron Arsenides: A Comparative Study of the Resistivity Anisotropy in Doped BaFe2As2 with Doping into Three Different Sites. J Am Chem Soc 2013; 135:3158-63. [DOI: 10.1021/ja311174e] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Shigeyuki Ishida
- Department
of Physics, University of Tokyo, Tokyo
113-0033, Japan
- National Institute of Advanced Industrial Science and Technology, Tsukuba
305-8568, Japan
- Transformative
Research Project
on Iron Pnictides, Japan Science and Technology Agency (JST), Tokyo 102-0075, Japan
| | - Masamichi Nakajima
- Department
of Physics, University of Tokyo, Tokyo
113-0033, Japan
- National Institute of Advanced Industrial Science and Technology, Tsukuba
305-8568, Japan
- Transformative
Research Project
on Iron Pnictides, Japan Science and Technology Agency (JST), Tokyo 102-0075, Japan
| | - Tian Liang
- Department
of Physics, University of Tokyo, Tokyo
113-0033, Japan
- National Institute of Advanced Industrial Science and Technology, Tsukuba
305-8568, Japan
- Transformative
Research Project
on Iron Pnictides, Japan Science and Technology Agency (JST), Tokyo 102-0075, Japan
| | - Kunihiro Kihou
- National Institute of Advanced Industrial Science and Technology, Tsukuba
305-8568, Japan
- Transformative
Research Project
on Iron Pnictides, Japan Science and Technology Agency (JST), Tokyo 102-0075, Japan
| | - Chul-Ho Lee
- National Institute of Advanced Industrial Science and Technology, Tsukuba
305-8568, Japan
- Transformative
Research Project
on Iron Pnictides, Japan Science and Technology Agency (JST), Tokyo 102-0075, Japan
| | - Akira Iyo
- National Institute of Advanced Industrial Science and Technology, Tsukuba
305-8568, Japan
- Transformative
Research Project
on Iron Pnictides, Japan Science and Technology Agency (JST), Tokyo 102-0075, Japan
| | - Hiroshi Eisaki
- National Institute of Advanced Industrial Science and Technology, Tsukuba
305-8568, Japan
- Transformative
Research Project
on Iron Pnictides, Japan Science and Technology Agency (JST), Tokyo 102-0075, Japan
| | - Teruhisa Kakeshita
- Department
of Physics, University of Tokyo, Tokyo
113-0033, Japan
- Transformative
Research Project
on Iron Pnictides, Japan Science and Technology Agency (JST), Tokyo 102-0075, Japan
| | - Yasuhide Tomioka
- National Institute of Advanced Industrial Science and Technology, Tsukuba
305-8568, Japan
- Transformative
Research Project
on Iron Pnictides, Japan Science and Technology Agency (JST), Tokyo 102-0075, Japan
| | - Toshimitsu Ito
- National Institute of Advanced Industrial Science and Technology, Tsukuba
305-8568, Japan
- Transformative
Research Project
on Iron Pnictides, Japan Science and Technology Agency (JST), Tokyo 102-0075, Japan
| | - Shin-ichi Uchida
- Department
of Physics, University of Tokyo, Tokyo
113-0033, Japan
- Transformative
Research Project
on Iron Pnictides, Japan Science and Technology Agency (JST), Tokyo 102-0075, Japan
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21
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Bernardo PL, Ghivelder L, Eslava GG, Amorim HS, Sinnecker EHC, Felner I, Neumeier JJ, García S. Magnetic and thermal responses triggered by structural changes in the double perovskite Sr2YRuO6. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2012; 24:486001. [PMID: 23137933 DOI: 10.1088/0953-8984/24/48/486001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Among double perovskites, the interpretation of the magnetic, thermal and transport properties of Sr(2)YRuO(6) remains a challenge. Characterization using different techniques reveals a variety of features that are not understood, described as anomalous, and yields contradictory values for several relevant parameters. We solved this situation through detailed susceptibility, specific heat, thermal expansion and x-ray diffraction measurements, including a quantitative correlation of the parameters characterizing the so-called anomalies. The emergence of short-range magnetic correlations, surviving well above the long-range transition, naturally accounts for the observed unconventional behavior of this compound. High resolution x-ray powder diffraction and thermal expansion results conclusively show that the magnetic and thermal responses are driven by lattice changes, providing a comprehensive scenario in which the interplay between the spin and structural degrees of freedom plays a relevant role.
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Affiliation(s)
- P L Bernardo
- Instituto de Física, Universidade Federal do Rio de Janeiro, Cidade Universitária, Rio de Janeiro, Brazil
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22
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Marchetti PA, Gambaccini M. Gauge approach to the 'pseudogap' phenomenology of the spectral weight in high Tc cuprates. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2012; 24:475601. [PMID: 23103555 DOI: 10.1088/0953-8984/24/47/475601] [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
We assume the t-t'-J model to describe the CuO(2) planes of hole-doped cuprates and we adapt the spin-charge gauge approach, previously developed for the t-J model, to describe the holes in terms of a spinless fermion carrying the charge (holon) and a neutral boson carrying spin 1/2 (spinon), coupled by a slave-particle gauge field. In this framework we consider the effects of a finite density of incoherent holon pairs in the normal state. Below a crossover temperature, identified as the experimental 'upper pseudogap', the scattering of the 'quanta' of the phase of the holon-pair field against holons reproduces the phenomenology of nodal Fermi arcs coexisting with a gap in the antinodal region. We thus obtain a microscopic derivation of the main features of the hole spectra due to the pseudogap. This result is obtained through a holon Green function which follows naturally from the formalism and analytically interpolates between a Fermi liquid-like and a d-wave superconductor behaviour as the coherence length of the holon-pair order parameter increases. By inserting the gauge coupling with the spinon we construct explicitly the hole Green function and calculate its spectral weight and the corresponding density of states. So we prove that the formation of holon pairs induces a depletion of states on the hole Fermi surface. We compare our results with ARPES and tunnelling experimental data. In our approach the hole preserves a finite Fermi surface until the superconducting transition, where it reduces to four nodes. Therefore we propose that the gap seen in the normal phase of cuprates is due to the thermal broadening of the SC-like peaks masking the Fermi-liquid peak in the spectral weight. The Fermi arcs then correspond to the region of the Fermi surface where the Fermi-liquid peak is unmasked.
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Affiliation(s)
- P A Marchetti
- Dipartimento di Fisica e Astronomia, Università di Padova and INFN, I-35131 Padova, Italy.
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23
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Fujimoto Y, Miyake K. Mode-mode coupling theory of itinerant electron antiferromagnetism in superconducting state. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2012; 24:405701. [PMID: 22945370 DOI: 10.1088/0953-8984/24/40/405701] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
It has been considered since the first discovery of a high-T(c) cuprate that an antiferromagnetic (AF) state and a superconducting (SC) state are separated in it. However, it is very intriguing that the coexistence of the AF and SC states has recently been observed in HgBa(2)Ca(4)Cu(5)O(12+) (Hg-1245). Moreover, it is very novel that this coexistence of these two states appears if the SC-transition temperature T(c) is higher than the AF-transition temperature T(N). The mode-mode coupling theory can provide a clear elucidation of this novel phenomenon. A key point of this theory is that the AF susceptibility consists of the random-phase-approximation (RPA) term and the mode-mode coupling one. The RPA term works to make a positive contribution to the emergence of the antiferromagnetic critical point (AF-CP). In contrast, the mode-mode coupling term works to make a negative contribution to the emergence of the AF-CP. However, the growth of the SC-gap function in the d(x(2)-y(2))-wave SC state works to suppress the negative contribution of the mode-mode coupling term to the emergence of the AF-CP. Moreover, the effect of SC fluctuations near the SC-transition temperature T(c) suppresses the mode-mode coupling term of the AF susceptibility that works to hinder the AF ordering. For these two reasons, there is a possibility that the d(x(2)-y(2))-wave SC state is likely to promote the emergence of the AF-CP. Namely, the appearance of the above-mentioned novel coexistence of the AF and SC states observed in Hg-1245 can be explained qualitatively on the basis of this idea.
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Affiliation(s)
- Yukinobu Fujimoto
- Division of Materials Physics, Department of Materials Engineering Science, Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531, Japan.
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24
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Dean MPM, Springell RS, Monney C, Zhou KJ, Pereiro J, Božović I, Dalla Piazza B, Rønnow HM, Morenzoni E, van den Brink J, Schmitt T, Hill JP. Spin excitations in a single La2CuO4 layer. NATURE MATERIALS 2012; 11:850-854. [PMID: 22941330 DOI: 10.1038/nmat3409] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/21/2011] [Accepted: 07/26/2012] [Indexed: 05/27/2023]
Abstract
Cuprates and other high-temperature superconductors consist of two-dimensional layers that are crucial to their properties. The dynamics of the quantum spins in these layers lie at the heart of the mystery of the cuprates. In bulk cuprates such as La(2)CuO(4), the presence of a weak coupling between the two-dimensional layers stabilizes a three-dimensional magnetic order up to high temperatures. In a truly two-dimensional system however, thermal spin fluctuations melt long-range order at any finite temperature. Here, we measure the spin response of isolated layers of La(2)CuO(4) that are only one-unit-cell-thick. We show that coherent magnetic excitations, magnons, known from the bulk order, persist even in a single layer of La(2)CuO(4), with no evidence for more complex correlations such as resonating valence bond correlations. These magnons are, therefore, well described by spin-wave theory (SWT). On the other hand, we also observe a high-energy magnetic continuum in the isotropic magnetic response that is not well described by two-magnon SWT, or indeed any existing theories.
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Affiliation(s)
- M P M Dean
- Department of Condensed Matter Physics and Materials Science, Brookhaven National Laboratory, Upton, New York 11973, USA.
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25
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Fujiyama S, Ohsumi H, Komesu T, Matsuno J, Kim BJ, Takata M, Arima T, Takagi H. Two-dimensional Heisenberg behavior of J(eff)=1/2 isospins in the paramagnetic state of the spin-orbital Mott insulator Sr2IrO4. PHYSICAL REVIEW LETTERS 2012; 108:247212. [PMID: 23004324 DOI: 10.1103/physrevlett.108.247212] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/06/2012] [Indexed: 06/01/2023]
Abstract
The dynamical correlations of J(eff)=1/2 isospins in the paramagnetic state of spin-orbital Mott insulator Sr2IrO4 were revealed by resonant magnetic x-ray diffuse scattering. We found a two-dimensional antiferromagnetic fluctuation with a large in-plane correlation length exceeding 100 lattice spacings at even 20 K above the magnetic ordering temperature. In marked contrast to the naive expectation of the strong magnetic anisotropy associated with an enhanced spin-orbit coupling, we discovered an isotropic isospin correlation that is well described by the two-dimensional S=1/2 quantum Heisenberg model. The estimated antiferromagnetic coupling constant as large as J∼0.1 eV that is comparable to the small Mott gap (<0.5 eV) points out the weak and marginal Mott character of this spin-orbital entangled system.
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Affiliation(s)
- S Fujiyama
- RIKEN Advanced Science Institute, Wako 351-0198, Japan.
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26
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Xian Y. Longitudinal excitations in quantum antiferromagnets. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2011; 23:346003. [PMID: 21841234 DOI: 10.1088/0953-8984/23/34/346003] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
By extending our recently proposed magnon-density waves to low dimensions, we investigate, using a microscopic many-body approach, the longitudinal excitations of the quasi-one-dimensional (quasi-1d) and quasi-2d Heisenberg antiferromagnetic systems on a bipartite lattice with a general spin quantum number. We obtain the full energy spectrum of the longitudinal mode as a function of the coupling constants in the original lattice Hamiltonian and find that it always has a nonzero energy gap if the ground state has a long-range order and becomes gapless for the pure isotropic 1d model. The numerical value of the minimum gap in our approximation agrees with that of a longitudinal mode observed in the quasi-1d antiferromagnetic compound KCuF3 at low temperature. It will be interesting to compare values of the energy spectrum at other momenta if their experimental results are available.
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Affiliation(s)
- Y Xian
- School of Physics and Astronomy, University of Manchester, Manchester M13 9PL, UK
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27
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Larionov IA. Toward a theory for low-frequency spin dynamics in plane copper oxide superconductors: crossover from localized spins to weak coupling charge carriers with doping. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2011; 23:245702. [PMID: 21625036 DOI: 10.1088/0953-8984/23/24/245702] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
We explore for all wavevectors through the Brillouin zone the dynamic spin susceptibility χ(total)(+,-)(ω, q) that takes into account the interplay of localized and itinerant charge carriers. The imaginary part, Imχ(total)(+,-)(ω, q), has peaks at the antiferromagnetic wavevector Q = (π, π) and a diffusive-like, extremely narrow and sharp peak (symmetric ring of maxima |q| = q(0)) at very small wavevectors Q(0) is proportional to w/J ≈ 10(-6) with the nuclear magnetic/quadrupole resonance frequency ω and the superexchange coupling constant J. We demonstrate the capability of Imχ(total)(+,-)(ω, q) for plane copper (63)(1/T(1)) and oxygen (17)(1/T(1)) nuclear spin-lattice relaxation rate calculations from carrier free right up to optimally doped La(2 - x)Sr(x)CuO(4) and obtain the basic features of temperature and doping behavior for (63)(1/T(1)) in agreement with experimental observations.
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Affiliation(s)
- Igor A Larionov
- Magnetic Radiospectroscopy Laboratory, Institute of Physics, Kazan Federal University, Kazan, Russia.
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28
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Suter A, Morenzoni E, Prokscha T, Wojek BM, Luetkens H, Nieuwenhuys G, Gozar A, Logvenov G, Božović I. Two-dimensional magnetic and superconducting phases in metal-insulator La(2-x)Sr(x)CuO(4) superlattices measured by muon-spin rotation. PHYSICAL REVIEW LETTERS 2011; 106:237003. [PMID: 21770540 DOI: 10.1103/physrevlett.106.237003] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/30/2010] [Revised: 03/23/2011] [Indexed: 05/31/2023]
Abstract
We show, by means of low-energy muon-spin rotation measurements, that few-unit-cells thick La(2)CuO(4) layers synthesized digitally by molecular beam epitaxy are antiferromagnetically ordered. Below a thickness of about 5 CuO(2) layers the long-range ordered state breaks down, and a magnetic state appears with enhanced quantum fluctuations and a reduced spin stiffness. This magnetic state can exist in close proximity (few Å) to high-temperature superconducting layers, without transmitting supercurrents.
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Affiliation(s)
- A Suter
- Laboratory for Muon Spin Spectroscopy, Paul Scherrer Institute, 5232 Villigen PSI, Switzerland.
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Saha SR, Kirshenbaum K, Butch NP, Paglione J, Zavalij PY. Uniform chemical pressure effect in solid solutions Ba1-xSrxFe2As2and Sr1−xCaxFe2As2. ACTA ACUST UNITED AC 2011. [DOI: 10.1088/1742-6596/273/1/012104] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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30
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Kouno S, Shirakawa N, Yoshida Y, Umeyama N, Tokiwa K, Watanabe T. The synthesis under controlled oxygen partial pressure and the characterization of a layered perovskite system Sr(2)V(1-x)Mo(x)O(4). JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2009; 21:285601. [PMID: 21828521 DOI: 10.1088/0953-8984/21/28/285601] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
We have successfully synthesized Sr(2)V(1-x)Mo(x)O(4) from x = 0.3 to 1.0 by an improved process. The layered compound Sr(2)VO(4) is an antiferromagnetic insulator with S = 1/2, while the isostructural Sr(2)MoO(4) is a Pauli paramagnetic metal. The solid solution Sr(2)V(1-x)Mo(x)O(4) of these materials is expected to show a metal-insulator transition. In this paper we report the synthetic process and the results of the magnetic susceptibility and the electrical resistivity. The selection of the starting materials and the adjustment of O(2) partial pressure of less than 10(-12) atm were indispensable for the synthesis. The reducing conditions during the sintering had been determined rationally, according to thermodynamical analysis. Kondo-like behavior in both resistivity and magnetic susceptibility were observed in a limited range of V-containing samples.
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Affiliation(s)
- Shinji Kouno
- Nanoelectronics Research Institute, Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki 305-8568, Japan. Department of Applied Electronics, Tokyo University of Science, Noda, Chiba 278-8510, Japan
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31
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Illas F. Ab INITIO COMPUTATIONAL MODELS IN MATERIALS SCIENCE: A COMMON PLAYGROUND FOR SURFACE CHEMISTRY AND SOLID-STATE PHYSICS. CHEM ENG COMMUN 2008. [DOI: 10.1080/00986440801967338] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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32
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Hinkov V, Haug D, Fauqué B, Bourges P, Sidis Y, Ivanov A, Bernhard C, Lin CT, Keimer B. Electronic liquid crystal state in the high-temperature superconductor YBa2Cu3O6.45. Science 2008; 319:597-600. [PMID: 18187621 DOI: 10.1126/science.1152309] [Citation(s) in RCA: 111] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Electronic phases with symmetry properties matching those of conventional liquid crystals have recently been discovered in transport experiments on semiconductor heterostructures and metal oxides at millikelvin temperatures. We report the spontaneous onset of a one-dimensional, incommensurate modulation of the spin system in the high-transition-temperature superconductor YBa2Cu3O6.45 upon cooling below approximately 150 kelvin, whereas static magnetic order is absent above 2 kelvin. The evolution of this modulation with temperature and doping parallels that of the in-plane anisotropy of the resistivity, indicating an electronic nematic phase that is stable over a wide temperature range. The results suggest that soft spin fluctuations are a microscopic route toward electronic liquid crystals and that nematic order can coexist with high-temperature superconductivity in underdoped cuprates.
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Affiliation(s)
- V Hinkov
- Max-Planck-Institut für Festkörperforschung, Heisenberg-strasse 1, D-70569 Stuttgart, Germany.
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33
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Fishman AY, Mitrofanov VY. Pressure Dependence of Exchange Parameters and Neel Temperature in La2CuO4. Isr J Chem 2007. [DOI: 10.1560/ijc.47.3-4.357] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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34
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Berg E, Fradkin E, Kim EA, Kivelson SA, Oganesyan V, Tranquada JM, Zhang SC. Dynamical layer decoupling in a stripe-ordered high-T(c) superconductor. PHYSICAL REVIEW LETTERS 2007; 99:127003. [PMID: 17930544 DOI: 10.1103/physrevlett.99.127003] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/03/2007] [Indexed: 05/25/2023]
Abstract
In the stripe-ordered state of a strongly correlated two-dimensional electronic system, under a set of special circumstances, the superconducting condensate, like the magnetic order, can occur at a nonzero wave vector corresponding to a spatial period double that of the charge order. In this case, the Josephson coupling between near neighbor planes, especially in a crystal with the special structure of La(2-x)Ba(x)CuO(4), vanishes identically. We propose that this is the underlying cause of the dynamical decoupling of the layers recently observed in transport measurements at x = 1/8.
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Affiliation(s)
- E Berg
- Department of Physics, Stanford University, Stanford, California 94305-4060, USA
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35
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Pérez-Jiménez AJ, Pérez-Jordá JM, Sancho-García JC. Combining two-body density correlation functionals with multiconfigurational wave functions using natural orbitals and occupation numbers. J Chem Phys 2007; 127:104102. [PMID: 17867732 DOI: 10.1063/1.2770713] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We propose a procedure that combines multiconfigurational (MC) wave functions with two-body density correlation functionals by transforming the latter into functionals of the MC natural orbitals and occupation numbers. The method is tested with the spectroscopic constants of a set of 11 diatomics, the diradical-involved automerization barrier of cyclobutadiene, the energy difference between triplet and open-shell singlet states in He and the methylene molecule, and the magnetic coupling constants of several systems, such as NiO, KNiF(3), K(2)NiF(4), La(2)CuO(4), alpha-4-dehydrotoluene, 1,1('),5,5(')-tetramethyl-6,6(')-dioxo-3,3(')-biverdazyl, [Cu(2)Cl(6)](-2), copper(II) acetate monohidrate and H-He-H. The procedure is applied to the Colle-Salvetti [Theor. Chim. Acta 37, 329 (1975); 53, 55 (1979)], functional and to a size-consistent functional depending on the on-top pair density (F1-5-N(eff)). On average, the best results are provided by the transformed F1-5-N(eff) [J. Chem. Phys. 114, 2022 (2001)] functional.
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36
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Lipscombe OJ, Hayden SM, Vignolle B, McMorrow DF, Perring TG. Persistence of high-frequency spin fluctuations in overdoped superconducting La2-xSrxCuO4 (x=0.22). PHYSICAL REVIEW LETTERS 2007; 99:067002. [PMID: 17930856 DOI: 10.1103/physrevlett.99.067002] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/15/2007] [Indexed: 05/25/2023]
Abstract
We report a detailed inelastic neutron scattering study of the collective magnetic excitations of overdoped superconducting La(1.78)Sr(0.22)CuO(4) for the energy range 0-160 meV. Our measurements show that overdoping suppresses the strong response present for optimally doped La(2-x)Sr(x)CuO(4) which is peaked near 50 meV. The remaining response is peaked at incommensurate wave vectors for all energies investigated. We observe a strong high-frequency magnetic response for E approximately >80 meV suggesting that significant antiferromagnetic exchange couplings persist well into the overdoped part of the cuprate phase diagram.
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Affiliation(s)
- O J Lipscombe
- H.H. Wills Physics Laboratory, University of Bristol, Tyndall Avenue, Bristol, BS8 1TL, United Kingdom
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37
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Motoyama EM, Yu G, Vishik IM, Vajk OP, Mang PK, Greven M. Spin correlations in the electron-doped high-transition-temperature superconductor Nd2-xCexCuO4±δ. Nature 2007; 445:186-9. [PMID: 17215839 DOI: 10.1038/nature05437] [Citation(s) in RCA: 179] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2006] [Accepted: 11/09/2006] [Indexed: 11/09/2022]
Abstract
High-transition-temperature (high-T(c)) superconductivity develops near antiferromagnetic phases, and it is possible that magnetic excitations contribute to the superconducting pairing mechanism. To assess the role of antiferromagnetism, it is essential to understand the doping and temperature dependence of the two-dimensional antiferromagnetic spin correlations. The phase diagram is asymmetric with respect to electron and hole doping, and for the comparatively less-studied electron-doped materials, the antiferromagnetic phase extends much further with doping and appears to overlap with the superconducting phase. The archetypal electron-doped compound Nd2-xCexCuO4+/-delta (NCCO) shows bulk superconductivity above x approximately 0.13 (refs 3, 4), while evidence for antiferromagnetic order has been found up to x approximately 0.17 (refs 2, 5, 6). Here we report inelastic magnetic neutron-scattering measurements that point to the distinct possibility that genuine long-range antiferromagnetism and superconductivity do not coexist. The data reveal a magnetic quantum critical point where superconductivity first appears, consistent with an exotic quantum phase transition between the two phases. We also demonstrate that the pseudogap phenomenon in the electron-doped materials, which is associated with pronounced charge anomalies, arises from a build-up of spin correlations, in agreement with recent theoretical proposals.
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Affiliation(s)
- E M Motoyama
- Department of Physics, Stanford University, Stanford, California 94305, USA
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38
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Pérez-Jiménez AJ, Pérez-Jordá JM, Moreira IDPR, Illas F. Merging multiconfigurational wavefunctions and correlation functionals to predict magnetic coupling constants. J Comput Chem 2007; 28:2559-68. [PMID: 17486552 DOI: 10.1002/jcc.20757] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
We study the performance of different approaches that combine multiconfigurational wavefunctions with correlation functionals for the calculation of magnetic coupling constants of several materials and molecules. The systems under study include four antiferromagnetic materials: NiO, KNiF(3), K(2)NiF(4) and La(2)CuO(4); two biradicals: alpha-4-Dehydrotoluene and 1,1',5,5'-Tetramethyl-6,6'-dioxo-3,3'-biverdazyl; two molecular complexes: [Cu(2)Cl(6)](-2) and Copper(II) acetate monohidrate; and the prototypical H-He-H system. On average, the best results are obtained with a recently proposed method [Phys. Rev. A 75, 012503 (2007)] that estimates the correlation energy of density functionals from a pair of alternative spin densities built from the natural orbitals and occupation numbers of the multiconfigurational wavefunction.
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39
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Moreira IDPR, Calzado CJ, Malrieu JP, Illas F. First-principles periodic calculation of four-body spin terms in high-Tc cuprate superconductors. PHYSICAL REVIEW LETTERS 2006; 97:087003. [PMID: 17026325 DOI: 10.1103/physrevlett.97.087003] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/18/2005] [Indexed: 05/12/2023]
Abstract
A general mapping between the energy of pertinent magnetic solutions and the diagonal terms of the spin Hamiltonian in a local representation provides the first general framework to extract accurate values for the many body terms of extended spin Hamiltonians from periodic first-principle calculations. Estimates of these terms for La2CuO4, the paradigm of high-Tc superconductor parent compounds, and for the SrCu2O3 ladder compound are reported. For La2CuO4, present results support experimental evidence by Toader et al. [Phys. Rev. Lett. 94, 197202 (2005)10.1103/PhysRevLett.94.197202]. For SrCu2O3 even larger four-body spin amplitudes are found together with Jl/Jr = 1 and non-negligible ferromagnetic interladder exchange.
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Affiliation(s)
- Ibério de P R Moreira
- Departament de Química Física and Centre Especial de Recerca en Química Teòrica, Universitat de Barcelona and Parc Científic de Barcelona, C/ Martí i Franquès 1, E-08028 Barcelona, Spain
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40
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Pérez-Jiménez AJ, Pérez-Jordá JM, Illas F. Density functional theory with alternative spin densities: application to magnetic systems with localized spins. J Chem Phys 2005; 120:18-25. [PMID: 15267256 DOI: 10.1063/1.1630021] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
A new method to improve the excess spin density obtained from unrestricted Hartree-Fock wave functions in terms of natural orbitals is proposed. Using this modified excess spin density to evaluate the correlation energy by means of density functionals leads to large improvements in the computed magnetic coupling constants of several materials without need to modify the exchange contribution. This is important because it reconciles the density functional theory description with the one provided by multi-determinant wave functions. Using the present approach, the leading contribution to the magnetic coupling constant arises from electron correlation effects. The performance of the new method is illustrated on various materials including high-critical-temperature superconductors parent compounds.
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41
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Sushkov OP, Kotov VN. Theory of incommensurate magnetic correlations across the insulator-superconductor transition of underdoped La2-xSrxCuO4. PHYSICAL REVIEW LETTERS 2005; 94:097005. [PMID: 15783992 DOI: 10.1103/physrevlett.94.097005] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/15/2004] [Indexed: 05/24/2023]
Abstract
The main feature in the elastic neutron scattering of La2-xSrxCuO4 is the existence of incommensurate peaks with positions that jump from 45 degrees to 0 degrees at 5% doping. We show that the spiral state of the t-t(')-t('')-J model with realistic parameters describes these data perfectly. We explain why in the insulator the peak is at 45 degrees while it switches to 0 degrees precisely at the insulator-metal transition. The calculated positions of the peaks are in agreement with the data in both phases.
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Affiliation(s)
- Oleg P Sushkov
- School of Physics, University of New South Wales, Sydney 2052, Australia.
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42
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Gozar A, Dennis BS, Blumberg G, Komiya S, Ando Y. Magnetic order in lightly doped La2-xSrxCuO4. PHYSICAL REVIEW LETTERS 2004; 93:027001. [PMID: 15323941 DOI: 10.1103/physrevlett.93.027001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/19/2003] [Indexed: 05/24/2023]
Abstract
We study long wavelength magnetic excitations in lightly doped La2-xSrxCuO4 (x</=0.03) detwinned crystals. The lowest energy magnetic anisotropy induced gap can be understood in terms of the antisymmetric spin interaction inside the antiferromagnetic (AF) phase. The second magnetic resonance, analyzed in terms of in-plane spin anisotropy, shows unconventional behavior within the AF state; it led to the discovery of collective spin excitations pertaining to a field induced magnetically ordered state. This state persists in a 9 T field to more than 100 K above the Néel temperature in x=0.01.
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Affiliation(s)
- A Gozar
- Bell Laboratories, Lucent Technologies, Murray Hill, New Jersey 07974, USA.
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43
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Mang PK, Vajk OP, Arvanitaki A, Lynn JW, Greven M. Spin correlations and magnetic order in nonsuperconducting Nd(2-x)Ce(x)CuO(4+/-delta). PHYSICAL REVIEW LETTERS 2004; 93:027002. [PMID: 15323942 DOI: 10.1103/physrevlett.93.027002] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/03/2003] [Indexed: 05/24/2023]
Abstract
We report quantitative neutron scattering measurements of the evolution with doping of the Néel temperature, the antiferromagnetic correlations, and the ordered moment of as-grown, nonsuperconducting Nd(2-x)Ce(x)CuO(4+/-delta) (0</=x</=0.18). The instantaneous correlation length can be effectively described by our quantum Monte Carlo calculations for the randomly site-diluted nearest-neighbor spin-1/2 square-lattice Heisenberg antiferromagnet. However, quantum fluctuations have a stronger effect on the ordered moment, which decreases more rapidly than for the quenched-disorder model.
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Affiliation(s)
- P K Mang
- Department of Applied Physics, Stanford University, Stanford, California 94305, USA
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44
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Dumm M, Komiya S, Ando Y, Basov DN. Anisotropic electromagnetic response of lightly doped La2-xSrxCuO4 within the CuO2 planes. PHYSICAL REVIEW LETTERS 2003; 91:077004. [PMID: 12935048 DOI: 10.1103/physrevlett.91.077004] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/16/2002] [Indexed: 05/24/2023]
Abstract
Using infrared spectroscopy, we show that spin self-organization in untwinned La2-xSrxCuO4 (LSCO) crystals has profound consequences for the dynamical conductivity sigma(omega). The electronic response of CuO2 planes acquires significant anisotropy in the spin ordered state with enhancement of the conductivity along the direction of the diagonal spin stripes by up to a factor of 2. An examination of the anisotropic response indicates that the diagonal spin texture in weakly doped LSCO is also accompanied by the modulation of charge density. The electronic response of the charge stripes is found to be gapless consistent with the hypothesis of the metallic ground state. Our experiments directly show that the striped ordered systems reveal new degrees of freedom not present in ordinary one-dimensional conductors.
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Affiliation(s)
- M Dumm
- Department of Physics, University of California at San Diego, La Jolla, CA 92093-0319, USA.
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45
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Kou SP, Weng ZY. Topological gauge structure and phase diagram for weakly doped antiferromagnets. PHYSICAL REVIEW LETTERS 2003; 90:157003. [PMID: 12732064 DOI: 10.1103/physrevlett.90.157003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/19/2002] [Indexed: 05/24/2023]
Abstract
We show that a topological gauge structure in an effective description of the t-J model gives rise to a global phase diagram of antiferromagnetic and superconducting phases in a weakly doped regime. Dual confinement and deconfinement of holons and spinons play essential roles here, with a quantum critical point at a doping concentration x(c) approximately equal to 0.043. The complex experimental phase diagram at low doping is well described within such a framework.
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Affiliation(s)
- Su-Peng Kou
- Department of Physics, Beijing Normal University, Beijing 100875, China
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46
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Thomsen C. Critical exponents and percolation thresholds in two-dimensional systems with a finite interplane coupling. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2002; 65:065104. [PMID: 12188773 DOI: 10.1103/physreve.65.065104] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/08/2001] [Indexed: 05/23/2023]
Abstract
Classical site percolation was used to study numerically the effect of interplane coupling in the range 10(-1)-10(-6) of the in-plane coupling on the static correlation length exponent nu and the critical dimension D. It was found that even for the smallest coupling values the exponents take their three-dimensional (3D) values for sufficiently large system sizes. The percolation threshold p(c), however, varies continuously from the 2D to the 3D value with a power-law exponent kappa=0.41(2), which, to within error, is the same for simple cubic, bcc, and fcc lattices. As predicted by renormalization-group theory this exponent equals the inverse of the susceptibility exponent gamma=43/18.
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Affiliation(s)
- C Thomsen
- Institut für Festkörperphysik, Technische Universität Berlin, Hardenbergstrasse 36, 10623 Berlin, Germany
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47
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Vajk OP, Mang PK, Greven M, Gehring PM, Lynn JW. Quantum impurities in the two-dimensional spin one-half Heisenberg antiferromagnet. Science 2002; 295:1691-5. [PMID: 11872834 DOI: 10.1126/science.1067110] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
The study of randomness in low-dimensional quantum antiferromagnets is at the forefront of research in the field of strongly correlated electron systems, yet there have been relatively few experimental model systems. Complementary neutron scattering and numerical experiments demonstrate that the spin-diluted Heisenberg antiferromagnet La2Cu1-z(Zn,Mg)(z)O4 is an excellent model material for square-lattice site percolation in the extreme quantum limit of spin one-half. Measurements of the ordered moment and spin correlations provide important quantitative information for tests of theories for this complex quantum-impurity problem.
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Affiliation(s)
- O P Vajk
- Department of Physics, Stanford University, Stanford, CA 94309, USA
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48
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Kopeć TK, Zaleski TA. Scaling near the quantum-critical point in the SO(5) theory of the high-T(c) superconductivity. PHYSICAL REVIEW LETTERS 2001; 87:097002. [PMID: 11531590 DOI: 10.1103/physrevlett.87.097002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/09/2001] [Indexed: 05/23/2023]
Abstract
We study the quantum-critical point scenario within the unified theory of superconductivity and antiferromagnetism based on the SO(5) symmetry. Closed-form expression for the quantum-critical scaling function for the dynamic spin susceptibility is obtained from the lattice SO(5) quantum nonlinear sigma-model in three dimensions, revealing that in the quantum-critical region the frequency scale for spin excitations is simply set by the absolute temperature. Implications for the non-Fermi liquid behavior of the normal-state resistivity due to spin fluctuations in the quantum-critical region are also presented.
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Affiliation(s)
- T K Kopeć
- Institute for Low Temperature and Structure Research, Polish Academy of Sciences, P.O. Box 1410, 50-950 Wrocław, Poland
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49
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Lavrov AN, Ando Y, Komiya S, Tsukada I. Unusual magnetic susceptibility anisotropy in untwinned La2-xSr(x)CuO4 single crystals in the lightly doped region. PHYSICAL REVIEW LETTERS 2001; 87:017007. [PMID: 11461491 DOI: 10.1103/physrevlett.87.017007] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/08/2001] [Indexed: 05/23/2023]
Abstract
We present a study of the magnetic susceptibility chi in carefully detwinned La 2-xSr(x)CuO4 single crystals in the lightly doped region (x = 0-0.03), which demonstrates a remarkable in-plane anisotropy of the spin system. This anisotropy, chi(a)/chi(b), is found to persist after the long-range antiferromagnetic (AF) order is destroyed by hole doping, suggesting that doped holes break the AF order into domains in which the spin alignment is kept essentially intact. It turns out that the freezing of the spins taking place at low temperatures is also notably anisotropic, implying that the "spin-glass" feature is governed by the domain structure as well.
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Affiliation(s)
- A N Lavrov
- Central Research Institute of Electric Power Industry, 2-11-1 Iwato-kita, Komae, Tokyo 201-8511 Japan
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50
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Coldea R, Hayden SM, Aeppli G, Perring TG, Frost CD, Mason TE, Cheong SW, Fisk Z. Spin waves and electronic interactions in La2CuO4. PHYSICAL REVIEW LETTERS 2001; 86:5377-5380. [PMID: 11384502 DOI: 10.1103/physrevlett.86.5377] [Citation(s) in RCA: 115] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/21/2000] [Indexed: 05/23/2023]
Abstract
The magnetic excitations of the square-lattice spin-1/2 antiferromagnet and high- T(c) parent compound La2CuO4 are determined using high-resolution inelastic neutron scattering. Sharp spin waves with absolute intensities in agreement with theory including quantum corrections are found throughout the Brillouin zone. The observed dispersion relation shows evidence for substantial interactions beyond the nearest-neighbor Heisenberg term which can be understood in terms of a cyclic or ring exchange due to the strong hybridization path around the Cu4O4 square plaquettes.
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Affiliation(s)
- R Coldea
- Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
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