1
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Oppliger J, Denner MM, Küspert J, Frison R, Wang Q, Morawietz A, Ivashko O, Dippel AC, Zimmermann MV, Biało I, Martinelli L, Fauqué B, Choi J, Garcia-Fernandez M, Zhou KJ, Christensen NB, Kurosawa T, Momono N, Oda M, Natterer FD, Fischer MH, Neupert T, Chang J. Weak signal extraction enabled by deep neural network denoising of diffraction data. NAT MACH INTELL 2024; 6:180-186. [PMID: 38404481 PMCID: PMC10883886 DOI: 10.1038/s42256-024-00790-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2022] [Accepted: 01/08/2024] [Indexed: 02/27/2024]
Abstract
The removal or cancellation of noise has wide-spread applications in imaging and acoustics. In applications in everyday life, such as image restoration, denoising may even include generative aspects, which are unfaithful to the ground truth. For scientific use, however, denoising must reproduce the ground truth accurately. Denoising scientific data is further challenged by unknown noise profiles. In fact, such data will often include noise from multiple distinct sources, which substantially reduces the applicability of simulation-based approaches. Here we show how scientific data can be denoised by using a deep convolutional neural network such that weak signals appear with quantitative accuracy. In particular, we study X-ray diffraction and resonant X-ray scattering data recorded on crystalline materials. We demonstrate that weak signals stemming from charge ordering, insignificant in the noisy data, become visible and accurate in the denoised data. This success is enabled by supervised training of a deep neural network with pairs of measured low- and high-noise data. We additionally show that using artificial noise does not yield such quantitatively accurate results. Our approach thus illustrates a practical strategy for noise filtering that can be applied to challenging acquisition problems.
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Affiliation(s)
- Jens Oppliger
- Physik-Institut, Universität Zürich, Zurich, Switzerland
| | | | - Julia Küspert
- Physik-Institut, Universität Zürich, Zurich, Switzerland
| | - Ruggero Frison
- Physik-Institut, Universität Zürich, Zurich, Switzerland
| | - Qisi Wang
- Physik-Institut, Universität Zürich, Zurich, Switzerland
- Department of Physics, The Chinese University of Hong Kong, Hong Kong, China
| | | | - Oleh Ivashko
- Deutsches Elektronen-Synchrotron DESY, Hamburg, Germany
| | | | | | - Izabela Biało
- Physik-Institut, Universität Zürich, Zurich, Switzerland
- Faculty of Physics and Applied Computer Science, AGH University of Krakow, Krakow, Poland
| | | | - Benoît Fauqué
- JEIP, USR 3573 CNRS, Collège de France, PSL University, Paris, France
| | | | | | | | | | - Tohru Kurosawa
- Department of Physics, Hokkaido University, Sapporo, Japan
| | - Naoki Momono
- Department of Physics, Hokkaido University, Sapporo, Japan
- Department of Applied Sciences, Muroran Institute of Technology, Muroran, Japan
| | - Migaku Oda
- Department of Physics, Hokkaido University, Sapporo, Japan
| | | | | | - Titus Neupert
- Physik-Institut, Universität Zürich, Zurich, Switzerland
| | - Johan Chang
- Physik-Institut, Universität Zürich, Zurich, Switzerland
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2
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Choi J, Wang Q, Jöhr S, Christensen NB, Küspert J, Bucher D, Biscette D, Fischer MH, Hücker M, Kurosawa T, Momono N, Oda M, Ivashko O, Zimmermann MV, Janoschek M, Chang J. Unveiling Unequivocal Charge Stripe Order in a Prototypical Cuprate Superconductor. Phys Rev Lett 2022; 128:207002. [PMID: 35657867 DOI: 10.1103/physrevlett.128.207002] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/22/2021] [Accepted: 04/13/2022] [Indexed: 06/15/2023]
Abstract
In the cuprates, high-temperature superconductivity, spin-density-wave order, and charge-density-wave (CDW) order are intertwined, and symmetry determination is challenging due to domain formation. We investigated the CDW in the prototypical cuprate La_{1.88}Sr_{0.12}CuO_{4} via x-ray diffraction employing uniaxial pressure as a domain-selective stimulus to establish the unidirectional nature of the CDW unambiguously. A fivefold enhancement of the CDW amplitude is found when homogeneous superconductivity is partially suppressed by magnetic field. This field-induced state provides an ideal search environment for a putative pair-density-wave state.
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Affiliation(s)
- J Choi
- Physik-Institut, Universität Zürich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland
| | - Q Wang
- Physik-Institut, Universität Zürich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland
| | - S Jöhr
- Physik-Institut, Universität Zürich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland
| | - N B Christensen
- Department of Physics, Technical University of Denmark, DK-2800 Kongens Lyngby, Denmark
| | - J Küspert
- Physik-Institut, Universität Zürich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland
| | - D Bucher
- Physik-Institut, Universität Zürich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland
| | - D Biscette
- Physik-Institut, Universität Zürich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland
| | - M H Fischer
- Physik-Institut, Universität Zürich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland
| | - M Hücker
- Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot 7610001, Israel
| | - T Kurosawa
- Department of Physics, Hokkaido University, Sapporo 060-0810, Japan
| | - N Momono
- Department of Physics, Hokkaido University, Sapporo 060-0810, Japan
- Department of Applied Sciences, Muroran Institute of Technology, Muroran 050-8585, Japan
| | - M Oda
- Department of Physics, Hokkaido University, Sapporo 060-0810, Japan
| | - O Ivashko
- Deutsches Elektronen-Synchrotron DESY, Notkestraße 85, 22607 Hamburg, Germany
| | - M V Zimmermann
- Deutsches Elektronen-Synchrotron DESY, Notkestraße 85, 22607 Hamburg, Germany
| | - M Janoschek
- Physik-Institut, Universität Zürich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland
- Laboratory for Neutron and Muon Instrumentation, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland
| | - J Chang
- Physik-Institut, Universität Zürich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland
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3
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Wang Q, Horio M, von Arx K, Shen Y, John Mukkattukavil D, Sassa Y, Ivashko O, Matt CE, Pyon S, Takayama T, Takagi H, Kurosawa T, Momono N, Oda M, Adachi T, Haidar SM, Koike Y, Tseng Y, Zhang W, Zhao J, Kummer K, Garcia-Fernandez M, Zhou KJ, Christensen NB, Rønnow HM, Schmitt T, Chang J. High-Temperature Charge-Stripe Correlations in La_{1.675}Eu_{0.2}Sr_{0.125}CuO_{4}. Phys Rev Lett 2020; 124:187002. [PMID: 32441965 DOI: 10.1103/physrevlett.124.187002] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/26/2019] [Revised: 03/02/2020] [Accepted: 04/14/2020] [Indexed: 06/11/2023]
Abstract
We use resonant inelastic x-ray scattering to investigate charge-stripe correlations in La_{1.675}Eu_{0.2}Sr_{0.125}CuO_{4}. By differentiating elastic from inelastic scattering, it is demonstrated that charge-stripe correlations precede both the structural low-temperature tetragonal phase and the transport-defined pseudogap onset. The scattering peak amplitude from charge stripes decays approximately as T^{-2} towards our detection limit. The in-plane integrated intensity, however, remains roughly temperature independent. Therefore, although the incommensurability shows a remarkably large increase at high temperature, our results are interpreted via a single scattering constituent. In fact, direct comparison to other stripe-ordered compounds (La_{1.875}Ba_{0.125}CuO_{4}, La_{1.475}Nd_{0.4}Sr_{0.125}CuO_{4}, and La_{1.875}Sr_{0.125}CuO_{4}) suggests a roughly constant integrated scattering intensity across all these compounds. Our results therefore provide a unifying picture for the charge-stripe ordering in La-based cuprates. As charge correlations in La_{1.675}Eu_{0.2}Sr_{0.125}CuO_{4} extend beyond the low-temperature tetragonal and pseudogap phase, their emergence heralds a spontaneous symmetry breaking in this compound.
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Affiliation(s)
- Qisi Wang
- Physik-Institut, Universität Zürich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland
| | - M Horio
- Physik-Institut, Universität Zürich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland
| | - K von Arx
- Physik-Institut, Universität Zürich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland
| | - Y Shen
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433, China
| | - D John Mukkattukavil
- Department of Physics and Astronomy, Uppsala University, Box 516, SE-751 20 Uppsala, Sweden
| | - Y Sassa
- Department of Physics, Chalmers University of Technology, SE-412 96 Göteborg, Sweden
| | - O Ivashko
- Physik-Institut, Universität Zürich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland
| | - C E Matt
- Physik-Institut, Universität Zürich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland
- Swiss Light Source, Photon Science Division, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland
| | - S Pyon
- Department of Advanced Materials, University of Tokyo, Kashiwa 277-8561, Japan
| | - T Takayama
- Department of Advanced Materials, University of Tokyo, Kashiwa 277-8561, Japan
| | - H Takagi
- Department of Advanced Materials, University of Tokyo, Kashiwa 277-8561, Japan
| | - T Kurosawa
- Department of Physics, Hokkaido University, Sapporo 060-0810, Japan
| | - N Momono
- Department of Physics, Hokkaido University, Sapporo 060-0810, Japan
- Department of Applied Sciences, Muroran Institute of Technology, Muroran 050-8585, Japan
| | - M Oda
- Department of Physics, Hokkaido University, Sapporo 060-0810, Japan
| | - T Adachi
- Department of Engineering and Applied Sciences, Sophia University, Tokyo 102-8554, Japan
| | - S M Haidar
- Department of Applied Physics, Tohoku University, Sendai 980-8579, Japan
| | - Y Koike
- Department of Applied Physics, Tohoku University, Sendai 980-8579, Japan
| | - Y Tseng
- Swiss Light Source, Photon Science Division, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland
| | - W Zhang
- Swiss Light Source, Photon Science Division, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland
| | - J Zhao
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433, China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing 210093, China
| | - K Kummer
- European Synchrotron Radiation Facility, 71 Avenue des Martyrs, 38043 Grenoble, France
| | - M Garcia-Fernandez
- Diamond Light Source, Harwell Campus, Didcot, Oxfordshire OX11 0DE, United Kingdom
| | - Ke-Jin Zhou
- Diamond Light Source, Harwell Campus, Didcot, Oxfordshire OX11 0DE, United Kingdom
| | - N B Christensen
- Department of Physics, Technical University of Denmark, DK-2800 Kongens Lyngby, Denmark
| | - H M Rønnow
- Institute of Physics, École Polytechnique Fedérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
| | - T Schmitt
- Swiss Light Source, Photon Science Division, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland
| | - J Chang
- Physik-Institut, Universität Zürich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland
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4
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Wan W, Christensen NB, Sandvik AW, Tregenna-Piggott P, Nilsen GJ, Mourigal M, Perring TG, Frost CD, McMorrow DF, Rønnow HM. Temperature dependence of the [Formula: see text] anomaly in the excitation spectrum of the 2D quantum Heisenberg antiferromagnet. J Phys Condens Matter 2020; 32:374007. [PMID: 32050188 DOI: 10.1088/1361-648x/ab757a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
It is well established that in the low-temperature limit, the two-dimensional quantum Heisenberg antiferromagnet on a square lattice (2DQHAFSL) exhibits an anomaly in its spectrum at short-wavelengths on the zone-boundary. In the vicinity of the [Formula: see text] point the pole in the one-magnon response exhibits a downward dispersion, is heavily damped and attenuated, giving way to an isotropic continuum of excitations extending to high energies. The origin of the anomaly and the presence of the continuum are of current theoretical interest, with suggestions focused around the idea that the latter evidences the existence of spinons in a two-dimensional system. Here we present the results of neutron inelastic scattering experiments and Quantum Monte Carlo calculations on the metallo-organic compound Cu(DCOO)[Formula: see text]D2O (CFTD), an excellent physical realisation of the 2DQHAFSL, designed to investigate how the anomaly at [Formula: see text] evolves up to finite temperatures [Formula: see text]. Our data reveal that on warming the anomaly survives the loss of long-range, three-dimensional order, and that it is thus a robust feature of the two-dimensional system. With further increase of temperature the zone-boundary response gradually softens and broadens, washing out the [Formula: see text] anomaly. This is confirmed by a comparison of our data with the results of finite-temperature Quantum Monte Carlo simulations where the two are found to be in good accord. In the vicinity of the antiferromagnetic zone centre, there was no significant softening of the magnetic excitations over the range of temperatures investigated.
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Affiliation(s)
- W Wan
- Department of Physics, Technical University of Denmark, DK-2800 Kongens Lyngby, Denmark
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5
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Ivashko O, Horio M, Wan W, Christensen NB, McNally DE, Paris E, Tseng Y, Shaik NE, Rønnow HM, Wei HI, Adamo C, Lichtensteiger C, Gibert M, Beasley MR, Shen KM, Tomczak JM, Schmitt T, Chang J. Strain-engineering Mott-insulating La 2CuO 4. Nat Commun 2019; 10:786. [PMID: 30783084 PMCID: PMC6381167 DOI: 10.1038/s41467-019-08664-6] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2018] [Accepted: 01/20/2019] [Indexed: 11/10/2022] Open
Abstract
The transition temperature Tc of unconventional superconductivity is often tunable. For a monolayer of FeSe, for example, the sweet spot is uniquely bound to titanium-oxide substrates. By contrast for La2-xSrxCuO4 thin films, such substrates are sub-optimal and the highest Tc is instead obtained using LaSrAlO4. An outstanding challenge is thus to understand the optimal conditions for superconductivity in thin films: which microscopic parameters drive the change in Tc and how can we tune them? Here we demonstrate, by a combination of x-ray absorption and resonant inelastic x-ray scattering spectroscopy, how the Coulomb and magnetic-exchange interaction of La2CuO4 thin films can be enhanced by compressive strain. Our experiments and theoretical calculations establish that the substrate producing the largest Tc under doping also generates the largest nearest neighbour hopping integral, Coulomb and magnetic-exchange interaction. We hence suggest optimising the parent Mott state as a strategy for enhancing the superconducting transition temperature in cuprates.
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Affiliation(s)
- O Ivashko
- Physik-Institut, Universität Zürich, Winterthurerstrasse 190, CH-8057, Zürich, Switzerland.
| | - M Horio
- Physik-Institut, Universität Zürich, Winterthurerstrasse 190, CH-8057, Zürich, Switzerland
| | - W Wan
- Department of Physics, Technical University of Denmark, DK-2800, Kongens Lyngby, Denmark
| | - N B Christensen
- Department of Physics, Technical University of Denmark, DK-2800, Kongens Lyngby, Denmark
| | - D E McNally
- Photon Science Division, Swiss Light Source, Paul Scherrer Institut, CH-5232, Villigen PSI, Switzerland
| | - E Paris
- Photon Science Division, Swiss Light Source, Paul Scherrer Institut, CH-5232, Villigen PSI, Switzerland
| | - Y Tseng
- Photon Science Division, Swiss Light Source, Paul Scherrer Institut, CH-5232, Villigen PSI, Switzerland
| | - N E Shaik
- Institute of Physics, École Polytechnique Fedérale de Lausanne (EPFL), CH-1015, Lausanne, Switzerland
| | - H M Rønnow
- Institute of Physics, École Polytechnique Fedérale de Lausanne (EPFL), CH-1015, Lausanne, Switzerland
| | - H I Wei
- Department of Physics, Laboratory of Atomic and Solid State Physics, Cornell University, Ithaca, NY, 14853, USA
| | - C Adamo
- Department of Applied Physics, Stanford University, Stanford, CA, 94305, USA
| | - C Lichtensteiger
- Department of Quantum Matter Physics, University of Geneva, 24 Quai Ernest Ansermet, 1211, Geneva, Switzerland
| | - M Gibert
- Physik-Institut, Universität Zürich, Winterthurerstrasse 190, CH-8057, Zürich, Switzerland
| | - M R Beasley
- Department of Applied Physics, Stanford University, Stanford, CA, 94305, USA
| | - K M Shen
- Department of Physics, Laboratory of Atomic and Solid State Physics, Cornell University, Ithaca, NY, 14853, USA
| | - J M Tomczak
- Institute of Solid State Physics, Vienna University of Technology, A-1040, Vienna, Austria
| | - T Schmitt
- Photon Science Division, Swiss Light Source, Paul Scherrer Institut, CH-5232, Villigen PSI, Switzerland
| | - J Chang
- Physik-Institut, Universität Zürich, Winterthurerstrasse 190, CH-8057, Zürich, Switzerland
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6
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Markó M, Groitl F, Birk JO, Freeman PG, Lefmann K, Christensen NB, Niedermayer C, Jurányi F, Lass J, Hansen A, Rønnow HM. Prototype of the novel CAMEA concept-A backend for neutron spectrometers. Rev Sci Instrum 2018; 89:015105. [PMID: 29390677 DOI: 10.1063/1.5018233] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
The continuous angle multiple energy analysis concept is a backend for both time-of-flight and analyzer-based neutron spectrometers optimized for neutron spectroscopy with highly efficient mapping in the horizontal scattering plane. The design employs a series of several upward scattering analyzer arcs placed behind each other, which are set to different final energies allowing a wide angular coverage with multiple energies recorded simultaneously. For validation of the concept and the model calculations, a prototype was installed at the Swiss neutron source SINQ, Paul Scherrer Institut. The design of the prototype, alignment and calibration procedures, experimental results of background measurements, and proof-of-concept inelastic measurements on LiHoF4 and h-YMnO3 are presented here.
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Affiliation(s)
- Márton Markó
- Laboratory of Neutron Scattering and Imaging, Paul Scherrer Institut, 5232 Villigen PSI, Switzerland
| | - Felix Groitl
- Laboratory of Neutron Scattering and Imaging, Paul Scherrer Institut, 5232 Villigen PSI, Switzerland
| | - Jonas Okkels Birk
- Niels Bohr Institute, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen, Denmark
| | - Paul Gregory Freeman
- Laboratory for Quantum Magnetism, Institute of Physics, École Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland
| | - Kim Lefmann
- Niels Bohr Institute, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen, Denmark
| | | | - Christof Niedermayer
- Laboratory of Neutron Scattering and Imaging, Paul Scherrer Institut, 5232 Villigen PSI, Switzerland
| | - Fanni Jurányi
- Laboratory of Neutron Scattering and Imaging, Paul Scherrer Institut, 5232 Villigen PSI, Switzerland
| | - Jakob Lass
- Niels Bohr Institute, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen, Denmark
| | - Allan Hansen
- Niels Bohr Institute, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen, Denmark
| | - Henrik M Rønnow
- Laboratory for Quantum Magnetism, Institute of Physics, École Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland
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7
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Chang J, Blackburn E, Ivashko O, Holmes AT, Christensen NB, Hücker M, Liang R, Bonn DA, Hardy WN, Rütt U, Zimmermann MV, Forgan EM, Hayden SM. Magnetic field controlled charge density wave coupling in underdoped YBa2Cu3O6+x. Nat Commun 2016; 7:11494. [PMID: 27146255 PMCID: PMC4858734 DOI: 10.1038/ncomms11494] [Citation(s) in RCA: 116] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2016] [Accepted: 04/01/2016] [Indexed: 11/09/2022] Open
Abstract
The application of magnetic fields to layered cuprates suppresses their high-temperature superconducting behaviour and reveals competing ground states. In widely studied underdoped YBa2Cu3O6+x (YBCO), the microscopic nature of field-induced electronic and structural changes at low temperatures remains unclear. Here we report an X-ray study of the high-field charge density wave (CDW) in YBCO. For hole dopings ∼0.123, we find that a field (B∼10 T) induces additional CDW correlations along the CuO chain (b-direction) only, leading to a three-dimensional (3D) ordered state along this direction at B∼15 T. The CDW signal along the a-direction is also enhanced by field, but does not develop an additional pattern of correlations. Magnetic field modifies the coupling between the CuO2 bilayers in the YBCO structure, and causes the sudden appearance of the 3D CDW order. The mirror symmetry of individual bilayers is broken by the CDW at low and high fields, allowing Fermi surface reconstruction, as recently suggested.
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Affiliation(s)
- J Chang
- Physik-Institut, Universität Zürich, Winterthurerstrasse 190, Zürich CH-8057, Switzerland
| | - E Blackburn
- School of Physics and Astronomy, University of Birmingham, Birmingham B15 2TT, UK
| | - O Ivashko
- Physik-Institut, Universität Zürich, Winterthurerstrasse 190, Zürich CH-8057, Switzerland
| | - A T Holmes
- European Spallation Source ERIC, Box 176, Lund SE-221 00, Sweden
| | - N B Christensen
- Department of Physics, Technical University of Denmark, Kongens Lyngby DK-2800, Denmark
| | - M Hücker
- Condensed Matter Physics &Materials Science Department, Brookhaven National Lab, Upton, New York 11973, USA
| | - Ruixing Liang
- Department of Physics &Astronomy, University of British Columbia, Vancouver V6T-1Z1, Canada.,Canadian Institute for Advanced Research, Toronto M5G-1Z8, Canada
| | - D A Bonn
- Department of Physics &Astronomy, University of British Columbia, Vancouver V6T-1Z1, Canada.,Canadian Institute for Advanced Research, Toronto M5G-1Z8, Canada
| | - W N Hardy
- Department of Physics &Astronomy, University of British Columbia, Vancouver V6T-1Z1, Canada.,Canadian Institute for Advanced Research, Toronto M5G-1Z8, Canada
| | - U Rütt
- Deutsches Elektronen-Synchrotron DESY, 22603 Hamburg, Germany
| | - M V Zimmermann
- Deutsches Elektronen-Synchrotron DESY, 22603 Hamburg, Germany
| | - E M Forgan
- School of Physics and Astronomy, University of Birmingham, Birmingham B15 2TT, UK
| | - S M Hayden
- H.H. Wills Physics Laboratory, University of Bristol, Bristol BS8 1TL, UK
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8
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Piazza BD, Mourigal M, Christensen NB, Nilsen GJ, Tregenna-Piggott P, Perring TG, Enderle M, McMorrow DF, Ivanov DA, Rønnow HM. Fractional excitations in the square lattice quantum antiferromagnet. Nat Phys 2015; 11:62-68. [PMID: 25729400 PMCID: PMC4340518 DOI: 10.1038/nphys3172] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/10/2014] [Accepted: 10/29/2014] [Indexed: 05/30/2023]
Abstract
Quantum magnets have occupied the fertile ground between many-body theory and low-temperature experiments on real materials since the early days of quantum mechanics. However, our understanding of even deceptively simple systems of interacting spins-1/2 is far from complete. The quantum square-lattice Heisenberg antiferromagnet (QSLHAF), for example, exhibits a striking anomaly of hitherto unknown origin in its magnetic excitation spectrum. This quantum effect manifests itself for excitations propagating with the specific wave vector (π, 0). We use polarized neutron spectroscopy to fully characterize the magnetic fluctuations in the metal-organic compound CFTD, a known realization of the QSLHAF model. Our experiments reveal an isotropic excitation continuum at the anomaly, which we analyse theoretically using Gutzwiller-projected trial wavefunctions. The excitation continuum is accounted for by the existence of spatially-extended pairs of fractional S=1/2 quasiparticles, 2D analogues of 1D spinons. Away from the anomalous wave vector, these fractional excitations are bound and form conventional magnons. Our results establish the existence of fractional quasiparticles in the high-energy spectrum of a quasi-two-dimensional antiferromagnet, even in the absence of frustration.
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Affiliation(s)
- B Dalla Piazza
- Laboratory for Quantum Magnetism, École Polytechnique Fédérale de Lausanne (EPFL), CH-1015, Switzerland
| | - M Mourigal
- Laboratory for Quantum Magnetism, École Polytechnique Fédérale de Lausanne (EPFL), CH-1015, Switzerland ; Institut Laue-Langevin, BP 156, F-38042 Grenoble Cedex 9, France ; Institute for Quantum Matter and Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218, USA
| | - N B Christensen
- Department of Physics, Technical University of Denmark (DTU), DK-2800 Kgs. Lyngby, Denmark ; Laboratory for Neutron Scattering, Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland
| | - G J Nilsen
- Laboratory for Quantum Magnetism, École Polytechnique Fédérale de Lausanne (EPFL), CH-1015, Switzerland ; Department of Chemistry, University of Edinburgh, Edinburgh, EH9 3JJ, United Kingdom
| | - P Tregenna-Piggott
- Laboratory for Neutron Scattering, Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland
| | - T G Perring
- ISIS Facility, Rutherford Appleton Laboratory, Chilton, Didcot, Oxon OX11 OQX, United Kingdom
| | - M Enderle
- Institut Laue-Langevin, BP 156, F-38042 Grenoble Cedex 9, France
| | - D F McMorrow
- London Centre for Nanotechnology and Department of Physics and Astronomy, University College London, London WC1H 0AH, United Kingdom
| | - D A Ivanov
- Institute for Theoretical Physics, ETH Zürich, CH-8093 Zürich, Switzerland ; Institute for Theoretical Physics, University of Zürich, CH-8057 Zürich, Switzerland
| | - H M Rønnow
- Laboratory for Quantum Magnetism, École Polytechnique Fédérale de Lausanne (EPFL), CH-1015, Switzerland ; RIKEN Centre for Emergent Matter Science (CEMS), Wako 351-0198, Japan
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9
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Udby L, Larsen J, Christensen NB, Boehm M, Niedermayer C, Mohottala HE, Jensen TBS, Toft-Petersen R, Chou FC, Andersen NH, Lefmann K, Wells BO. Measurement of unique magnetic and superconducting phases in oxygen-doped high-temperature superconductors La(2-x)Sr(x)CuO(4+y). Phys Rev Lett 2013; 111:227001. [PMID: 24329465 DOI: 10.1103/physrevlett.111.227001] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/11/2013] [Indexed: 06/03/2023]
Abstract
We present a combined magnetic neutron scattering and muon spin rotation study of the nature of the magnetic and superconducting phases in electronically phase separated La(2-x)Sr(x)CuO(4+y), x=0.04, 0.065, 0.09. For all samples, we find long-range modulated magnetic order below T(N) is approximately equal to Tc=39 K. In sharp contrast to oxygen-stoichiometric La(2-x)Sr(x)CuO(4), we find that the magnetic propagation vector as well as the ordered magnetic moment is independent of Sr content and consistent with that of the "striped" cuprates. Our study provides direct proof that superoxygenation in La(2-x)Sr(x)CuO(4+y) allows the spin stripe ordered phase to emerge and phase separate from superconducting regions with the hallmarks of optimally doped oxygen-stoichiometric La(2-x)Sr(x)CuO(4).
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Affiliation(s)
- L Udby
- Nanoscience Center, Niels Bohr Institute, University of Copenhagen, DK-2100 Copenhagen, Denmark
| | - J Larsen
- Department of Physics, Technical University of Denmark, DK-2800 Kongens Lyngby, Denmark
| | - N B Christensen
- Department of Physics, Technical University of Denmark, DK-2800 Kongens Lyngby, Denmark
| | - M Boehm
- Institut Laue-Langevin, 38042 Grenoble Cedex 9, France
| | - Ch Niedermayer
- Laboratory for Neutron Scattering, Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland
| | - H E Mohottala
- University of Hartford, West Hartford, Connecticut 06117, USA
| | - T B S Jensen
- Department of Physics, Technical University of Denmark, DK-2800 Kongens Lyngby, Denmark
| | - R Toft-Petersen
- Department of Physics, Technical University of Denmark, DK-2800 Kongens Lyngby, Denmark and Helmholtz Zentrum Berlin für Materialien und Energie, D-14109 Berlin, Germany
| | - F C Chou
- Center for Condensed Matter Sciences, National Taiwan University, Taipei 10617, Taiwan
| | - N H Andersen
- Department of Physics, Technical University of Denmark, DK-2800 Kongens Lyngby, Denmark
| | - K Lefmann
- Nanoscience Center, Niels Bohr Institute, University of Copenhagen, DK-2100 Copenhagen, Denmark
| | - B O Wells
- Department of Physics, University of Connecticut, Storrs, Connecticut 06269-3046, USA
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10
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Blackburn E, Chang J, Hücker M, Holmes AT, Christensen NB, Liang R, Bonn DA, Hardy WN, Rütt U, Gutowski O, von Zimmermann M, Forgan EM, Hayden SM. X-ray diffraction observations of a charge-density-wave order in superconducting ortho-II YBa2Cu3O6.54 single crystals in zero magnetic field. Phys Rev Lett 2013; 110:137004. [PMID: 23581362 DOI: 10.1103/physrevlett.110.137004] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/16/2012] [Indexed: 06/02/2023]
Abstract
X-ray diffraction measurements show that the high-temperature superconductor YBa2Cu3O6.54, with ortho-II oxygen order, has charge-density-wave order in the absence of an applied magnetic field. The dominant wave vector of the charge density wave is q(CDW)=(0,0.328(2),0.5), with the in-plane component parallel to the b axis (chain direction). It has a similar incommensurability to that observed in ortho-VIII and ortho-III samples, which have different dopings and oxygen orderings. Our results for ortho-II contrast with recent high-field NMR measurements, which suggest a commensurate wave vector along the a axis. We discuss the relationship between spin and charge correlations in YBa2Cu3O(y) and recent high-field quantum oscillation, NMR, and ultrasound experiments.
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Affiliation(s)
- E Blackburn
- School of Physics and Astronomy, University of Birmingham, Birmingham B15 2TT, United Kingdom
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11
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Hong T, Kim YH, Hotta C, Takano Y, Tremelling G, Turnbull MM, Landee CP, Kang HJ, Christensen NB, Lefmann K, Schmidt KP, Uhrig GS, Broholm C. Field-induced Tomonaga-Luttinger liquid phase of a two-leg spin-1/2 ladder with strong leg interactions. Phys Rev Lett 2010; 105:137207. [PMID: 21230808 DOI: 10.1103/physrevlett.105.137207] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/29/2010] [Revised: 07/19/2010] [Indexed: 05/30/2023]
Abstract
We study the magnetic-field-induced quantum phase transition from a gapped quantum phase that has no magnetic long-range order into a gapless phase in the spin-1/2 ladder compound bis(2,3-dimethylpyridinium) tetrabromocuprate (DIMPY). At temperatures below about 1 K, the specific heat in the gapless phase attains an asymptotic linear temperature dependence, characteristic of a Tomonaga-Luttinger liquid. Inelastic neutron scattering and the specific heat measurements in both phases are in good agreement with theoretical calculations, demonstrating that DIMPY is the first model material for an S=1/2 two-leg spin ladder in the strong-leg regime.
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Affiliation(s)
- Tao Hong
- Neutron Scattering Science Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
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12
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Balédent V, Fauqué B, Sidis Y, Christensen NB, Pailhès S, Conder K, Pomjakushina E, Mesot J, Bourges P. Two-dimensional orbital-like magnetic order in the high-temperature La(2-x)Sr(x)CuO4 superconductor. Phys Rev Lett 2010; 105:027004. [PMID: 20867731 DOI: 10.1103/physrevlett.105.027004] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/19/2010] [Indexed: 05/29/2023]
Abstract
In high-temperature copper oxide superconductors, a novel magnetic order associated with the pseudogap phase has been identified in two different cuprate families over a wide region of temperature and doping. We report here the observation below 120 K of a similar magnetic ordering in the archetypal cuprate La(2-x)Sr(x)CuO4 (LSCO) system for x=0.085. In contrast with the previous reports, the magnetic ordering in LSCO is only short range with an in-plane correlation length of ∼10 A and is bidimensional (2D). Such a less pronounced order suggests an interaction with other electronic instabilities. In particular, LSCO also exhibits a strong tendency towards stripes ordering at the expense of the superconducting state.
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Affiliation(s)
- V Balédent
- Laboratoire Léon Brillouin, CEA-CNRS, CEA Saclay, 91191 Gif-sur-Yvette Cedex, France
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13
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Haug D, Hinkov V, Suchaneck A, Inosov DS, Christensen NB, Niedermayer C, Bourges P, Sidis Y, Park JT, Ivanov A, Lin CT, Mesot J, Keimer B. Magnetic-field-enhanced incommensurate magnetic order in the underdoped high-temperature superconductor YBa2Cu3O6.45. Phys Rev Lett 2009; 103:017001. [PMID: 19659170 DOI: 10.1103/physrevlett.103.017001] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/21/2009] [Indexed: 05/28/2023]
Abstract
We present a neutron-scattering study of the static and dynamic spin correlations in the underdoped high-temperature superconductor YBa2Cu3O6.45 in magnetic fields up to 15 T. The field strongly enhances static incommensurate magnetic order at low temperatures and induces a spectral-weight shift in the magnetic-excitation spectrum. A reconstruction of the Fermi surface driven by the field-enhanced magnetic superstructure may thus be responsible for the unusual Fermi surface topology revealed by recent quantum-oscillation experiments.
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Affiliation(s)
- D Haug
- Max-Planck-Institut für Festkörperforschung, Heisenbergstrasse 1, D-70569 Stuttgart, Germany
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14
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Prsa K, Rønnow HM, Zaharko O, Christensen NB, Jensen J, Chang J, Streule S, Jiménez-Ruiz M, Berger H, Prester M, Mesot J. Anomalous magnetic excitations of cooperative tetrahedral spin clusters. Phys Rev Lett 2009; 102:177202. [PMID: 19518821 DOI: 10.1103/physrevlett.102.177202] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/28/2008] [Indexed: 05/27/2023]
Abstract
An inelastic neutron scattering study of Cu2Te2O5X2 (X=Cl, Br) shows strong dispersive modes with large energy gaps persisting far above TN, notably in Cu2Te2O5Br2. The anomalous features: a coexisting unusually weak Goldstone-like mode observed in Cu2Te2O5Cl2 and the size of the energy gaps cannot be explained by existing theories, such as our mean-field or random-phase approximation. We argue that our findings represent a new general type of behavior due to intercluster quantum fluctuations and call for development of a new theoretical approach.
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Affiliation(s)
- K Prsa
- Laboratory for Neutron Scattering, ETH Zürich and Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland.
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15
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Chang J, Christensen NB, Niedermayer C, Lefmann K, Rønnow HM, McMorrow DF, Schneidewind A, Link P, Hiess A, Boehm M, Mottl R, Pailhés S, Momono N, Oda M, Ido M, Mesot J. Magnetic-field-induced soft-mode quantum phase transition in the high-temperature superconductor La1.855Sr0.145CuO4: an inelastic neutron-scattering study. Phys Rev Lett 2009; 102:177006. [PMID: 19518819 DOI: 10.1103/physrevlett.102.177006] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/21/2009] [Indexed: 05/27/2023]
Abstract
Inelastic neutron-scattering experiments on the high-temperature superconductor La1.855Sr0.145CuO4 reveal a magnetic excitation gap Delta that decreases continuously upon application of a magnetic field perpendicular to the CuO2 planes. The gap vanishes at the critical field required to induce long-range incommensurate antiferromagnetic order, providing compelling evidence for a field-induced soft-mode driven quantum phase transition.
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Affiliation(s)
- J Chang
- Laboratory for Neutron Scattering, ETH Zurich and PSI Villigen, CH-5232 Villigen PSI, Switzerland.
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16
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Park JT, Inosov DS, Niedermayer C, Sun GL, Haug D, Christensen NB, Dinnebier R, Boris AV, Drew AJ, Schulz L, Shapoval T, Wolff U, Neu V, Yang X, Lin CT, Keimer B, Hinkov V. Electronic phase separation in the slightly underdoped iron pnictide superconductor Ba1-xKxFe2As2. Phys Rev Lett 2009; 102:117006. [PMID: 19392233 DOI: 10.1103/physrevlett.102.117006] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/14/2008] [Indexed: 05/27/2023]
Abstract
Here we present a combined study of the slightly underdoped novel pnictide superconductor Ba1-xKxFe2As2 by means of x-ray powder diffraction, neutron scattering, muon-spin rotation (microSR), and magnetic force microscopy (MFM). Static antiferromagnetic order sets in below T{m} approximately 70 K as inferred from the neutron scattering and zero-field-microSR data. Transverse-field microSR below Tc shows a coexistence of magnetically ordered and nonmagnetic states, which is also confirmed by MFM imaging. We explain such coexistence by electronic phase separation into antiferromagnetic and superconducting- or normal-state regions on a lateral scale of several tens of nanometers. Our findings indicate that such mesoscopic phase separation can be considered an intrinsic property of some iron pnictide superconductors.
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Affiliation(s)
- J T Park
- Max-Planck-Institut für Festkörperforschung, Heisenbergstrasse 1, 70569 Stuttgart, Germany
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17
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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] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [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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18
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Waldman SA, Christensen NB, Terzic A. Evolution of Clinical Pharmacology and Therapeutics. Clin Pharmacol Ther 2007. [DOI: 10.1038/sj.clpt.6100314] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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19
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Christensen NB. Fragmentation: When Pulling Apart All Comes Together. Clin Pharmacol Ther 2007; 82:240. [PMID: 17700587 DOI: 10.1038/sj.clpt.6100315] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
It is easy to think of a journal as a firm entity, but the modus vivendi of a highly read journal such as CPT is quite the opposite. The launch of CPT Nature Network adds another dimension.
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20
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Christensen NB, Rønnow HM, Mesot J, Ewings RA, Momono N, Oda M, Ido M, Enderle M, McMorrow DF, Boothroyd AT. Nature of the magnetic order in the charge-ordered cuprate La1.48Nd0.4Sr0.12CuO4. Phys Rev Lett 2007; 98:197003. [PMID: 17677652 DOI: 10.1103/physrevlett.98.197003] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/10/2006] [Indexed: 05/16/2023]
Abstract
Using polarized neutron scattering we establish that the magnetic order in La(1.48)Nd(0.4)Sr(0.12)CuO(4) is either (i) one dimensionally modulated and collinear, consistent with the stripe model or (ii) two dimensionally modulated with a novel noncollinear structure. The measurements rule out a number of alternative models characterized by 2D electronic order or 1D helical spin order. The low-energy spin excitations are found to be primarily transversely polarized relative to the stripe ordered state, consistent with conventional spin waves.
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Affiliation(s)
- N B Christensen
- Laboratory for Neutron Scattering, ETH Zurich & Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland
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21
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Chang J, Schnyder AP, Gilardi R, Rønnow HM, Pailhes S, Christensen NB, Niedermayer C, McMorrow DF, Hiess A, Stunault A, Enderle M, Lake B, Sobolev O, Momono N, Oda M, Ido M, Mudry C, Mesot J. Magnetic-field-induced spin excitations and renormalized spin gap of the underdoped La1.895Sr0.105CuO4 superconductor. Phys Rev Lett 2007; 98:077004. [PMID: 17359052 DOI: 10.1103/physrevlett.98.077004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/07/2006] [Indexed: 05/14/2023]
Abstract
High-resolution neutron inelastic scattering experiments in applied magnetic fields have been performed on La1.895Sr0.105CuO4 (LSCO). In zero field, the temperature dependence of the low-energy peak intensity at the incommensurate momentum transfer QIC=(0.5,0.5+/-delta,0),(0.5+/-delta,0.5,0) exhibits an anomaly at the superconducting Tc which broadens and shifts to lower temperature upon the application of a magnetic field along the c axis. A field-induced enhancement of the spectral weight is observed, but only at finite energy transfers and in an intermediate temperature range. These observations establish the opening of a strongly downward renormalized spin gap in the underdoped regime of LSCO. This behavior contrasts with the observed doping dependence of most electronic energy features.
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Affiliation(s)
- J Chang
- Laboratory for Neutron Scattering, ETH Zurich and PSI Villigen, CH-5232 Villigen PSI, Switzerland
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22
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23
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Lake B, Lefmann K, Christensen NB, Aeppli G, McMorrow DF, Ronnow HM, Vorderwisch P, Smeibidl P, Mangkorntong N, Sasagawa T, Nohara M, Takagi H. Three-dimensionality of field-induced magnetism in a high-temperature superconductor. Nat Mater 2005; 4:658-62. [PMID: 16100515 DOI: 10.1038/nmat1452] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/06/2005] [Accepted: 06/30/2005] [Indexed: 05/04/2023]
Abstract
Many physical properties of high-temperature superconductors are two-dimensional phenomena derived from their square-planar CuO2 building blocks. This is especially true of the magnetism from the copper ions. As mobile charge carriers enter the CuO2 layers, the antiferromagnetism of the parent insulators, where each copper spin is antiparallel to its nearest neighbours, evolves into a fluctuating state where the spins show tendencies towards magnetic order of a longer periodicity. For certain charge-carrier densities, quantum fluctuations are sufficiently suppressed to yield static long-period order, and external magnetic fields also induce such order. Here we show that, in contrast to the chemically controlled order in superconducting samples, the field-induced order in these same samples is actually three-dimensional, implying significant magnetic linkage between the CuO2 planes. The results are important because they show that there are three-dimensional magnetic couplings that survive into the superconducting state, and coexist with the crucial inter-layer couplings responsible for three-dimensional superconductivity. Both types of coupling will straighten the vortex lines, implying that we have finally established a direct link between technical superconductivity, which requires zero electrical resistance in an applied magnetic field and depends on vortex dynamics, and the underlying antiferromagnetism of the cuprates.
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Affiliation(s)
- B Lake
- Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX1 3PU, UK.
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24
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Christensen NB, McMorrow DF, Rønnow HM, Lake B, Hayden SM, Aeppli G, Perring TG, Mangkorntong M, Nohara M, Takagi H. Dispersive excitations in the high-temperature superconductor La2-xSrxCuO4. Phys Rev Lett 2004; 93:147002. [PMID: 15524830 DOI: 10.1103/physrevlett.93.147002] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/17/2004] [Indexed: 05/24/2023]
Abstract
High-resolution neutron scattering experiments on optimally doped La2-xSrxCuO4 (x=0.16) reveal that the magnetic excitations are dispersive. The dispersion is the same as in YBa2Cu3O6.85, and is quantitatively related to that observed with charge sensitive probes. The associated velocity in La2-xSrxCuO4 is only weakly dependent on doping with a value close to the spin-wave velocity of the insulating (x=0) parent compound. In contrast with the insulator, the excitations broaden rapidly with increasing energy, forming a continuum at higher energy and bear a remarkable resemblance to multiparticle excitations observed in 1D S=1/2 antiferromagnets. The magnetic correlations are 2D, and so rule out the simplest scenarios where the copper oxide planes are subdivided into weakly interacting 1D magnets.
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Affiliation(s)
- N B Christensen
- Materials Research Department, Risø National Laboratory, 4000 Roskilde, Denmark
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25
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Lake B, Rønnow HM, Christensen NB, Aeppli G, Lefmann K, McMorrow DF, Vorderwisch P, Smeibidl P, Mangkorntong N, Sasagawa T, Nohara M, Takagi H, Mason TE. Antiferromagnetic order induced by an applied magnetic field in a high-temperature superconductor. Nature 2002; 415:299-302. [PMID: 11797002 DOI: 10.1038/415299a] [Citation(s) in RCA: 456] [Impact Index Per Article: 20.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
One view of the high-transition-temperature (high-Tc) copper oxide superconductors is that they are conventional superconductors where the pairing occurs between weakly interacting quasiparticles (corresponding to the electrons in ordinary metals), although the theory has to be pushed to its limit. An alternative view is that the electrons organize into collective textures (for example, charge and spin stripes) which cannot be 'mapped' onto the electrons in ordinary metals. Understanding the properties of the material would then need quantum field theories of objects such as textures and strings, rather than point-like electrons. In an external magnetic field, magnetic flux penetrates type II superconductors via vortices, each carrying one flux quantum. The vortices form lattices of resistive material embedded in the non-resistive superconductor, and can reveal the nature of the ground state-for example, a conventional metal or an ordered, striped phase-which would have appeared had superconductivity not intervened, and which provides the best starting point for a pairing theory. Here we report that for one high-Tc superconductor, the applied field that imposes the vortex lattice also induces 'striped' antiferromagnetic order. Ordinary quasiparticle models can account for neither the strength of the order nor the nearly field-independent antiferromagnetic transition temperature observed in our measurements.
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Affiliation(s)
- B Lake
- Oak Ridge National Laboratory, PO Box 2008 MS 6430, Oak Ridge, Tennessee 37831-6430, USA.
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26
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Schrøder PS, Christensen NB. [Compulsory measures in psychiatry. A review of the first year after introduction of the new law]. Ugeskr Laeger 1992; 154:1826-30. [PMID: 1509536] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
A prospective survey of all registered treatment or measures carried out against the wishes of the patients during the first year after enforcement of the new Danish legislation in 1989 in the Psychiatric Hospital in Aalborg is presented. A total of 376 treatment situations and measures were registered. These involved 235 patients. It was found that 79 forced admissions had occurred together with 36 situations where patients who had been admitted voluntarily were forced to remain in hospital. The survey does not demonstrate any major change in the pattern of enforced measures and treatment after introduction of the new legislation. The working conditions for the new advisors for patients prescribed by the new law are described. These were found to be badly paid, idealistic and hard working. The daily administration of the law has been found to be quite bureaucratic. In addition, complains by patients concerning enforced measures and treatment are described. It is found that no verdicts contradict the steps taken by the hospital.
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