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Tseng Y, Paris E, Schmidt KP, Zhang W, Asmara TC, Bag R, Strocov VN, Singh S, Schlappa J, Rønnow HM, Schmitt T. Momentum-resolved spin-conserving two-triplon bound state and continuum in a cuprate ladder. COMMUNICATIONS PHYSICS 2023; 6:138. [PMID: 38665396 PMCID: PMC11041747 DOI: 10.1038/s42005-023-01250-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/29/2022] [Accepted: 05/23/2023] [Indexed: 04/28/2024]
Abstract
Studying multi-particle elementary excitations has provided unique access to understand collective many-body phenomena in correlated electronic materials, paving the way towards constructing microscopic models. In this work, we perform O K-edge resonant inelastic X-ray scattering (RIXS) on the quasi-one-dimensional cuprate Sr 14 Cu 24 O 41 with weakly-doped spin ladders. The RIXS signal is dominated by a dispersing sharp mode ~ 270 meV on top of a damped incoherent component ~ 400-500 meV. Comparing with model calculations using the perturbative continuous unitary transformations method, the two components resemble the spin-conserving ΔS = 0 two-triplon bound state and continuum excitations in the spin ladders. Such multi-spin response with long-lived ΔS = 0 excitons is central to several exotic magnetic properties featuring Majorana fermions, yet remains unexplored given the generally weak cross-section with other experimental techniques. By investigating a simple spin-ladder model system, our study provides valuable insight into low-dimensional quantum magnetism.
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Affiliation(s)
- Yi Tseng
- Photon Science Division, Paul Scherrer Institut, Forschungstrasse 111, CH-5232 Villigen PSI, Switzerland
- Laboratory for Quantum Magnetism, Institute of Physics, École Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
- Present Address: Department of Physics, Massachusetts Institute of Technology, Cambridge, MA 02139 USA
| | - Eugenio Paris
- Photon Science Division, Paul Scherrer Institut, Forschungstrasse 111, CH-5232 Villigen PSI, Switzerland
| | - Kai P. Schmidt
- Department of Physics, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Staudtstraße 7, D-91058 Erlangen, Germany
| | - Wenliang Zhang
- Photon Science Division, Paul Scherrer Institut, Forschungstrasse 111, CH-5232 Villigen PSI, Switzerland
| | - Teguh Citra Asmara
- Photon Science Division, Paul Scherrer Institut, Forschungstrasse 111, CH-5232 Villigen PSI, Switzerland
| | - Rabindranath Bag
- Indian Institute of Science Education and Research, Dr. Homi Bhabha Road, Pune, Maharashtra 411008 India
- Present Address: Department of Physics, Duke University, Durham, NC 27708 USA
| | - Vladimir N. Strocov
- Photon Science Division, Paul Scherrer Institut, Forschungstrasse 111, CH-5232 Villigen PSI, Switzerland
| | - Surjeet Singh
- Indian Institute of Science Education and Research, Dr. Homi Bhabha Road, Pune, Maharashtra 411008 India
| | - Justine Schlappa
- Photon Science Division, Paul Scherrer Institut, Forschungstrasse 111, CH-5232 Villigen PSI, Switzerland
- European X-Ray Free-Electron Laser Facility GmbH, Holzkoppel 4, 22869 Schenefeld, Germany
| | - Henrik M. Rønnow
- Laboratory for Quantum Magnetism, Institute of Physics, École Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
| | - Thorsten Schmitt
- Photon Science Division, Paul Scherrer Institut, Forschungstrasse 111, CH-5232 Villigen PSI, Switzerland
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2
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Sarte PM, Wilson SD, Attfield JP, Stock C. Magnetic fluctuations and the spin-orbit interaction in Mott insulating CoO. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2020; 32:374011. [PMID: 32554874 DOI: 10.1088/1361-648x/ab8498] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/07/2019] [Accepted: 03/30/2020] [Indexed: 06/11/2023]
Abstract
Motivated by the presence of an unquenched orbital angular momentum in CoO, a team at Chalk River, including a recently hired research officer Roger Cowley, performed the first inelastic neutron scattering experiments on the classic Mott insulator [Sakuraiet al1968Phys. Rev.167510]. Despite identifying two magnon modes at the zone boundary, the team was unable to parameterise the low energy magnetic excitation spectrum belowTNusing conventional pseudo-bosonic approaches, instead achieving only qualitative agreement. It would not be for another 40 years that Roger, now at Oxford and motivated by the discovery of the high-Tccuprate superconductors [Bednorz and Muller 1986Z. Phys. B64189], would make another attempt at the parameterisation of the magnetic excitation spectrum that had previously alluded him at the start of his career. Upon his return to CoO, Roger found a system embroiled in controversy, with some of its most fundamental parameters still remaining undetermined. Faced with such a formidable task, Roger performed a series of inelastic neutron scattering experiments in the early 2010s on both CoO and a magnetically dilute structural analogue Mg0.97Co0.03O. These experiments would prove instrumental in the determination of both single-ion [Cowleyet al2013Phys. Rev. B88205117] and cooperative magnetic parameters [Sarteet al2018Phys. Rev. B98024415] for CoO. Both these sets of parameters would eventually be used in a spin-orbit exciton model [Sarteet al2019Phys. Rev. B100075143], developed by his longtime friend and collaborator Bill Buyers, to successfully parameterise the complex spectrum that both measured at Chalk River almost 50 years prior. The story of CoO is of one that has come full circle, one filled with both spectacular failures and intermittent, yet profound, little victories.
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Affiliation(s)
- P M Sarte
- California NanoSystems Institute, University of California, Santa Barbara, California 93106-6105, United States of America
- Materials Department, University of California, Santa Barbara, California 93106-5050, United States of America
- School of Chemistry, University of Edinburgh, Edinburgh EH9 3FJ, United Kingdom
- Centre for Science at Extreme Conditions, University of Edinburgh, Edinburgh EH9 3FD, United Kingdom
| | - S D Wilson
- California NanoSystems Institute, University of California, Santa Barbara, California 93106-6105, United States of America
- Materials Department, University of California, Santa Barbara, California 93106-5050, United States of America
| | - J P Attfield
- School of Chemistry, University of Edinburgh, Edinburgh EH9 3FJ, United Kingdom
- Centre for Science at Extreme Conditions, University of Edinburgh, Edinburgh EH9 3FD, United Kingdom
| | - C Stock
- Centre for Science at Extreme Conditions, University of Edinburgh, Edinburgh EH9 3FD, United Kingdom
- School of Physics and Astronomy, University of Edinburgh, Edinburgh EH9 3FD, United Kingdom
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3
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Novelli F, Tollerud JO, Prabhakaran D, Davis JA. Persistent coherence of quantum superpositions in an optimally doped cuprate revealed by 2D spectroscopy. SCIENCE ADVANCES 2020; 6:eaaw9932. [PMID: 32158934 PMCID: PMC7048423 DOI: 10.1126/sciadv.aaw9932] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/13/2019] [Accepted: 12/05/2019] [Indexed: 05/10/2023]
Abstract
Quantum materials displaying intriguing magnetic and electronic properties could be key to the development of future technologies. However, it is poorly understood how the macroscopic behavior emerges in complex materials with strong electronic correlations. While measurements of the dynamics of excited electronic populations have been able to give some insight, they have largely neglected the intricate dynamics of quantum coherence. Here, we apply multidimensional coherent spectroscopy to a prototypical cuprate and report unprecedented coherent dynamics persisting for ~500 fs, originating directly from the quantum superposition of optically excited states separated by 20 to 60 meV. These results reveal that the states in this energy range are correlated with the optically excited states at ~1.5 eV and point to nontrivial interactions between quantum many-body states on the different energy scales. In revealing these dynamics and correlations, we demonstrate that multidimensional coherent spectroscopy can interrogate complex quantum materials in unprecedented ways.
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Affiliation(s)
- Fabio Novelli
- Centre for Quantum and Optical Science, Swinburne University of Technology, Hawthorn, Victoria 3122, Australia
- Department of Physical Chemistry II, Ruhr University Bochum, 44801 Bochum, Germany
| | - Jonathan O. Tollerud
- Centre for Quantum and Optical Science, Swinburne University of Technology, Hawthorn, Victoria 3122, Australia
| | | | - Jeffrey A. Davis
- Centre for Quantum and Optical Science, Swinburne University of Technology, Hawthorn, Victoria 3122, Australia
- ARC Centre of Excellence for Future Low-Energy Electronics Technologies, Swinburne University of Technology, Hawthorn, Victoria 3122, Australia
- Corresponding author.
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4
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Abstract
We discuss a few possibilities of high- T c superconductivity with more than one orbital symmetry contributing to the pairing. First, we show that the high energies of orbital excitations in various cuprates suggest a simplified model with a single orbital of x 2 − y 2 symmetry doped by holes. Next, several routes towards involving both e g orbital symmetries for doped holes are discussed: (i) some give superconductivity in a CuO 2 monolayer on Bi2212 superconductors, Sr 2 CuO 4 − δ , Ba 2 CuO 4 − δ , while (ii) others as nickelate heterostructures or Eu 2 − x Sr x NiO 4 , could in principle realize it as well. At low electron filling of Ru ions, spin-orbital entangled states of t 2 g symmetry contribute in Sr 2 RuO 4 . Finally, electrons with both t 2 g and e g orbital symmetries contribute to the superconducting properties and nematicity of Fe-based superconductors, pnictides or FeSe. Some of them provide examples of orbital-selective Cooper pairing.
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Prosnikov MA, Smirnov AN, Yu Davydov V, Sablina KA, Pisarev RV. Lattice and magnetic dynamics of a quasi-one-dimensional chain antiferromagnet PbFeBO 4. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2017; 29:025808. [PMID: 27841995 DOI: 10.1088/0953-8984/29/2/025808] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
A group of recently synthesized orthorhombic Pnma crystals PbMBO4 (M = Cr, Mn, Fe) demonstrates a number of unusual structural and magnetic properties. We report on polarized Raman scattering study of the lattice and magnetic dynamics in single crystals of an antiferromagnet PbFeBO4 below and above [Formula: see text] K. Polarization properties of the observed magnetic excitations below T N as well as intense quasi-elastic scattering support the quasi-one-dimensional character of the magnetic structure of PbFeBO4. Frequency overlapping of magnetic excitations and low-frequency phonons in the range of 90-200 cm-1 leads to pronounced asymmetric anomalies thus confirming intrinsic coupling of magnetic and lattice subsystems. This conclusion is also supported by observation of anomalous temperature behaviour of higher frequency phonons in the vicinity of T N. Experimental investigations are supported by relevant magnetic symmetry analysis which allows us to explain previously observed anomalous results.
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Affiliation(s)
- M A Prosnikov
- Ioffe Physical-Technical Institute, Russian Academy of Sciences, 194021 St. Petersburg, Russia
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6
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Sugai S, Nohara J, Shiozaki R, Muroi T, Takayanagi Y, Hayamizu N, Takenaka K, Okazaki K. Correlation between Raman sum and optical conductivity sum in La(2-x)Sr(x)CuO4. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2013; 25:415701. [PMID: 24055839 DOI: 10.1088/0953-8984/25/41/415701] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
In a strongly correlated electron system, the single-particle spectral function changes into a coherent peak and incoherent humps which extend over 1 eV. The incoherent parts lose the symmetry and k dependence, so that the Raman spectra with different symmetries become identical and they are expressed by the optical conductivity. We found that the B1g and B2g spectra in La(2-x)Sr(x)CuO4 become identical above 2000 cm(-1) in the underdoped phase, if Fleury-Loudon type B1g two-magnon scattering is removed. The first Raman susceptibility moment correlates with the generalized optical conductivity moment. The good correlation arises from the incoherent states of a hump from 1000 to 4000 cm(-1). The hump is the only structure of the incoherent electronic states in the mid-infrared absorption spectra below 1.4 eV at low carrier densities. The energy is twice the separated dispersion segments of the spin wave in the k(perpendicular) stripe direction. The incoherent state is formed by the magnetic excitations created by the hole hopping in the antiferromagnetic spin stripes in the real space picture.
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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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7
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De Filippis G, Cataudella V, Nowadnick EA, Devereaux TP, Mishchenko AS, Nagaosa N. Quantum dynamics of the Hubbard-Holstein model in equilibrium and nonequilibrium: application to pump-probe phenomena. PHYSICAL REVIEW LETTERS 2012; 109:176402. [PMID: 23215207 DOI: 10.1103/physrevlett.109.176402] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/30/2012] [Indexed: 06/01/2023]
Abstract
The spectral response and physical features of the 2D Hubbard-Holstein model are calculated both in equilibrium at zero and low chemical dopings, and after an ultrashort powerful light pulse, in undoped systems. At equilibrium and at strong charge-lattice couplings, the optical conductivity reveals a three-peak structure in agreement with experimental observations. After an ultrashort pulse and at nonzero electron-phonon interaction, phonon and spin subsystems oscillate with the phonon period T(ph)≈80 fs. The decay time of the phonon oscillations is about 150-200 fs, similar to the relaxation time of the charge system. We propose a criterion for observing these oscillations in high T(c) compounds: the time span of the pump light pulse τ(pump) has to be shorter than the phonon oscillation period T(ph).
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Affiliation(s)
- G De Filippis
- SPIN-CNR and Dipartimento di Scienze Fisiche-Università di Napoli Federico II-I-80126 Napoli, Italy
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8
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Ab Initio determination of Cu 3d orbital energies in layered copper oxides. Sci Rep 2011; 1:65. [PMID: 22355584 PMCID: PMC3216552 DOI: 10.1038/srep00065] [Citation(s) in RCA: 83] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2011] [Accepted: 07/26/2011] [Indexed: 11/08/2022] Open
Abstract
It has long been argued that the minimal model to describe the low-energy physics of the high T(c) superconducting cuprates must include copper states of other symmetries besides the canonical [see text] one, in particular the [see text] orbital. Experimental and theoretical estimates of the energy splitting of these states vary widely. With a novel ab initio quantum chemical computational scheme we determine these energies for a range of copper-oxides and -oxychlorides, determine trends with the apical Cu-ligand distances and find excellent agreement with recent Resonant Inelastic X-ray Scattering measurements, available for La(2)CuO(4), Sr(2)CuO(2)Cl(2), and CaCuO(2).
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9
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Guarise M, Dalla Piazza B, Moretti Sala M, Ghiringhelli G, Braicovich L, Berger H, Hancock JN, van der Marel D, Schmitt T, Strocov VN, Ament LJP, van den Brink J, Lin PH, Xu P, Rønnow HM, Grioni M. Measurement of magnetic excitations in the two-dimensional antiferromagnetic Sr₂CuO₂Cl₂ insulator using resonant x-ray scattering: evidence for extended interactions. PHYSICAL REVIEW LETTERS 2010; 105:157006. [PMID: 21230933 DOI: 10.1103/physrevlett.105.157006] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/14/2010] [Indexed: 05/30/2023]
Abstract
We measured the momentum dependence of magnetic excitations in the model spin-1/2 2D antiferromagnetic insulator Sr2CuO2Cl2 (SCOC). We identify a single-spin-wave feature and a multimagnon continuum, with different polarization dependences. The spin waves display a large (70 meV) dispersion between the zone-boundary points (π, 0) and (π/2, π/2). Employing an extended t-t'-t''-U one-band Hubbard model, we find significant electronic hopping beyond nearest-neighbor Cu ions, indicative of extended magnetic interactions. The spectral line shape at (π, 0) indicates sizable quantum effects in SCOC and probably more generally in the cuprates.
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Affiliation(s)
- M Guarise
- Institute of Condensed Matter Physics, Ecole Polytechnique Fédérale de Lausanne, CH-1015, Switzerland
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10
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11
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Pfuner F, Degiorgi L, Berger H, Forró L. Infrared investigation of the phonon spectrum in the frustrated spin cluster compound FeTe(2)O(5)Cl. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2009; 21:375401. [PMID: 21832346 DOI: 10.1088/0953-8984/21/37/375401] [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 present our optical investigations on the frustrated spin cluster compound FeTe(2)O(5)Cl, which develops a long-range antiferromagnetic order below 10 K. We measure the optical reflectivity from the far-infrared to the ultraviolet with polarized light. We focus our attention on the lattice dynamics by discussing the infrared-active modes. Our findings reveal a polarization dependence of the vibrational modes but which do not seem to be affected by structural anomalies linked to the magnetically ordered state at low temperatures.
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Affiliation(s)
- F Pfuner
- Laboratorium für Festkörperphysik, ETH Zürich, CH-8093 Zürich, Switzerland
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12
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Shen ZX, Lanzara A, Ishihara S, Nagaosa N. Role of the electron-phonon interaction in the strongly correlated cuprate superconductors. ACTA ACUST UNITED AC 2009. [DOI: 10.1080/13642810208220725] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Affiliation(s)
- Z.-X. Shen
- a Department of Physics, Applied Physics and Stanford Synchrotron Radiation Laboratory , Stanford University , California , 94305 , USA
| | - A. Lanzara
- a Department of Physics, Applied Physics and Stanford Synchrotron Radiation Laboratory , Stanford University , California , 94305 , USA
- b Advanced Light Source, Lawrence Berkeley National Laboratory , Berkeley , California , 94720 , USA
| | - S. Ishihara
- c Department of Applied Physics , University of Tokyo , Bunkyo-ku, Tokyo , 113-8656 , Japan
| | - N. Nagaosa
- c Department of Applied Physics , University of Tokyo , Bunkyo-ku, Tokyo , 113-8656 , Japan
- d Correlated Electron Research Center, Agency of Industrial Science and Technology , Tsukuba , 305-0046 , Japan
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13
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Braicovich L, Ament LJP, Bisogni V, Forte F, Aruta C, Balestrino G, Brookes NB, De Luca GM, Medaglia PG, Granozio FM, Radovic M, Salluzzo M, van den Brink J, Ghiringhelli G. Dispersion of magnetic excitations in the cuprate La2CuO4 and CaCuO2 compounds measured using resonant x-ray scattering. PHYSICAL REVIEW LETTERS 2009; 102:167401. [PMID: 19518752 DOI: 10.1103/physrevlett.102.167401] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/22/2008] [Indexed: 05/27/2023]
Abstract
By resonant inelastic x-ray scattering in the soft x-ray regime we probe the dynamical multiple-spin correlations in the antiferromagnetic cuprates La2CuO4 and CaCuO2. High resolution measurements at the copper L3 edge allow the clear observation of dispersing bimagnon excitations. Theory based on the ultrashort core-hole lifetime expansion fits the data on these coherent spin excitations without free parameters.
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Affiliation(s)
- L Braicovich
- CNR-INFM Coherentia and Soft, Dipartimento di Fisica, Politecnico di Milano, I-20133 Milano, Italy
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14
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Mishchenko AS. Electron - phonon coupling in underdoped high-temperature superconductors. ACTA ACUST UNITED AC 2009. [DOI: 10.3367/ufnr.0179.200912b.1259] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022]
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15
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Hill JP, Blumberg G, Kim YJ, Ellis DS, Wakimoto S, Birgeneau RJ, Komiya S, Ando Y, Liang B, Greene RL, Casa D, Gog T. Observation of a 500 meV collective mode in La2-xSrxCuO4 and Nd2CuO4 using resonant inelastic X-ray scattering. PHYSICAL REVIEW LETTERS 2008; 100:097001. [PMID: 18352743 DOI: 10.1103/physrevlett.100.097001] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/20/2007] [Indexed: 05/26/2023]
Abstract
Utilizing resonant inelastic x-ray scattering, we report a previously unobserved mode in the excitation spectrum of La2-xSrxCuO4 and Nd2CuO4 at 500 meV. The mode is peaked around the (pi, 0) point in reciprocal space and is observed to soften, and broaden, away from this point. Samples with x=0, 0.01, 0.05, and 0.17 were studied. The new mode is found to be rapidly suppressed with increasing Sr content and is absent at x=0.17, where it is replaced by a continuum of excitations. This mode is only observed when the incident x-ray polarization is normal to the CuO planes.
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Affiliation(s)
- J P Hill
- Department of Condensed Matter Physics and Materials Science, Brookhaven National Laboratory, Upton, NY 11973, USA
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16
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Christensen NB, Rønnow HM, McMorrow DF, Harrison A, Perring TG, Enderle M, Coldea R, Regnault LP, Aeppli G. Quantum dynamics and entanglement of spins on a square lattice. Proc Natl Acad Sci U S A 2007; 104:15264-9. [PMID: 17884986 PMCID: PMC2000527 DOI: 10.1073/pnas.0703293104] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2006] [Indexed: 11/18/2022] Open
Abstract
Bulk magnetism in solids is fundamentally quantum mechanical in nature. Yet in many situations, including our everyday encounters with magnetic materials, quantum effects are masked, and it often suffices to think of magnetism in terms of the interaction between classical dipole moments. Whereas this intuition generally holds for ferromagnets, even as the size of the magnetic moment is reduced to that of a single electron spin (the quantum limit), it breaks down spectacularly for antiferromagnets, particularly in low dimensions. Considerable theoretical and experimental progress has been made in understanding quantum effects in one-dimensional quantum antiferromagnets, but a complete experimental description of even simple two-dimensional antiferromagnets is lacking. Here we describe a comprehensive set of neutron scattering measurements that reveal a non-spin-wave continuum and strong quantum effects, suggesting entanglement of spins at short distances in the simplest of all two-dimensional quantum antiferromagnets, the square lattice Heisenberg system.
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Affiliation(s)
- N B Christensen
- Materials Research Department, Risø National Laboratory, Technical University of Denmark, DK-4000 Roskilde, Denmark.
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17
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Kimura S, Hagiwara M, Ueda H, Narumi Y, Kindo K, Yashiro H, Kashiwagi T, Takagi H. Observation of higher-harmonic helical spin-resonance modes in the chromium spinel CdCr2O4. PHYSICAL REVIEW LETTERS 2006; 97:257202. [PMID: 17280386 DOI: 10.1103/physrevlett.97.257202] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/15/2005] [Revised: 08/04/2006] [Indexed: 05/13/2023]
Abstract
High frequency ESR measurements on the chromium spinel compound CdCr2O4 have been performed. The observed ESR modes below Hc' approximately 5.7 T can be explained well by the calculated resonance modes based on a molecular field theory assuming a helical spin structure. Other than the fundamental ones, we have succeeded in observing the higher-harmonic modes for the first time. A large change of the ESR modes above Hc' indicate that a variation of the spin structure from the helical to the four-sublattice canted one takes place around Hc'.
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Affiliation(s)
- S Kimura
- KYOKUGEN, Osaka University, Machikaneyama 1-3, Toyanaka 560-8531, Japan
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18
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Caimi G, Degiorgi L, Berger H, Forró L. Phonon analysis of the S = 1 quantum spin systems Ni(5)Te(4)O(12)X(2) (X = Cl and Br). JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2006; 18:4065-4070. [PMID: 21690757 DOI: 10.1088/0953-8984/18/16/012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
We report our investigations of the electrodynamic response of the S = 1 quantum spin systems Ni(5)Te(4)O(12)X(2) (X = Cl and Br), which develop a magnetic ordered state below 30 K. We measure the optical reflectivity over a broad spectral range extending from the far infrared up to the ultraviolet. Besides identifying the electronic interband transitions, we primarily focus our attention on the lattice dynamics, emphasizing the phonon modes spectrum and its temperature dependence. Our findings do not reveal any direct link between possible structural anomalies and the transition into the magnetically ordered state at low temperatures.
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Affiliation(s)
- G Caimi
- Laboratorium für Festkörperphysik, ETH Zürich, CH-8093 Zürich, Switzerland
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Takahashi JI, Hagita K, Kohn K, Tanabe Y, Hanamura E. Anomalously broad Raman scattering spectrum due to two-magnon excitation in hexagonal YMnO3. PHYSICAL REVIEW LETTERS 2002; 89:076404. [PMID: 12190539 DOI: 10.1103/physrevlett.89.076404] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/03/2001] [Indexed: 05/23/2023]
Abstract
A strong and broad Raman scattering (RS) spectrum is observed from two-magnon processes in YMnO3. The spectrum is analyzed by taking account (i) the magnon-exciton interaction and (ii) the magnon-phonon coupling in the intermediate state. Anomalous broadening of the RS is attributed to the large superexchange interaction between manganite ions and subsequent modification of magnons under the presence of the exciton and phonons in the intermediate state.
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Affiliation(s)
- Jun-Ichi Takahashi
- Japan Science and Technology Corporation (CREST), 758-65 Bibi, Chitose, Hokkaido 066-8655, Japan
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20
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Windt M, Grüninger M, Nunner T, Knetter C, Schmidt KP, Uhrig GS, Kopp T, Freimuth A, Ammerahl U, Büchner B, Revcolevschi A. Observation of two-magnon bound states in the two-leg ladders of (Ca,La)(14)Cu(24)O(41). PHYSICAL REVIEW LETTERS 2001; 87:127002. [PMID: 11580541 DOI: 10.1103/physrevlett.87.127002] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/21/2001] [Indexed: 05/23/2023]
Abstract
Phonon-assisted two-magnon absorption is studied in the spin- 1/2 two-leg ladders of (Ca,La)(14)Cu(24)O(41) for E parallel c (legs) and E parallel a (rungs). We verify the theoretically predicted existence of two-magnon singlet bound states, which give rise to peaks at approximately equal to 2140 and 2800 cm(-1). The two-magnon continuum is observed at approximately equal to 4000 cm(-1). Two different theoretical approaches (Jordan-Wigner fermions and perturbation theory) describe the data very well for J parallel approximately equal to 1020-1100 cm(-1), J parallel/J perpendicular approximately equal to 1-1.2. At high energies, the magnetic contribution to sigma(omega) is strikingly similar in the ladders and in the undoped high-T(c) cuprates, which emphasizes the importance of strong quantum fluctuations in the latter.
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Affiliation(s)
- M Windt
- II. Physikalisches Institut, Universität zu Köln, 50937 Köln, Germany
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Ho CM, Muthukumar VN, Ogata M, Anderson PW. Nature of spin excitations in two-dimensional mott insulators: undoped cuprates and other materials. PHYSICAL REVIEW LETTERS 2001; 86:1626-1629. [PMID: 11290209 DOI: 10.1103/physrevlett.86.1626] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/11/2000] [Indexed: 05/23/2023]
Abstract
We investigate the excitation spectrum of a two-dimensional resonating valence bond (RVB) state. Treating the pi-flux phase with antiferromagnetic correlations as a variational ground state, we recover the long wavelength magnon as an "RVB exciton." However, this excitation does not exhaust the entire spectral weight and the high-energy spectrum is dominated by fermionic excitations. The latter can be observed directly by inelastic neutron scattering, and we predict their characteristic energy scales along different high symmetry directions in the magnetic Brillouin zone. We also interpret experimental results on two magnon Raman scattering and midinfrared absorption within this scenario.
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Affiliation(s)
- C M Ho
- Department of Applied Physics, University of Tokyo, Japan
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Wang YY, Zhang FC, Dravid VP, Ng KK, Klein MV, Schnatterly SE, Miller LL. Momentum-Dependent Charge Transfer Excitations in Sr2CuO 2Cl2 Angle-Resolved Electron Energy Loss Spectroscopy. PHYSICAL REVIEW LETTERS 1996; 77:1809-1812. [PMID: 10063177 DOI: 10.1103/physrevlett.77.1809] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
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Zibold A, Liu HL, Moore SW, Graybeal JM, Tanner DB. Optical properties of single-crystal Sr2CuO2Cl2. PHYSICAL REVIEW. B, CONDENSED MATTER 1996; 53:11734-11743. [PMID: 9982798 DOI: 10.1103/physrevb.53.11734] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Perkins JD, Kleinberg DS, Kastner MA, Birgeneau RJ, Endoh Y, Yamada K, Hosoya S. Infrared optical excitations in La2NiO4. PHYSICAL REVIEW. B, CONDENSED MATTER 1995; 52:R9863-R9866. [PMID: 9980133 DOI: 10.1103/physrevb.52.r9863] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Lorenzana J, Sawatzky GA. Theory of phonon-assisted multimagnon optical absorption and bimagnon states in quantum antiferromagnets. PHYSICAL REVIEW. B, CONDENSED MATTER 1995; 52:9576-9589. [PMID: 9980006 DOI: 10.1103/physrevb.52.9576] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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