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Shen Y, Liu C, Qin Y, Shen S, Li YD, Bewley R, Schneidewind A, Chen G, Zhao J. Intertwined dipolar and multipolar order in the triangular-lattice magnet TmMgGaO 4. Nat Commun 2019; 10:4530. [PMID: 31594940 PMCID: PMC6783407 DOI: 10.1038/s41467-019-12410-3] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2018] [Accepted: 09/09/2019] [Indexed: 11/09/2022] Open
Abstract
A phase transition is often accompanied by the appearance of an order parameter and symmetry breaking. Certain magnetic materials exhibit exotic hidden-order phases, in which the order parameters are not directly accessible to conventional magnetic measurements. Thus, experimental identification and theoretical understanding of a hidden order are difficult. Here we combine neutron scattering and thermodynamic probes to study the newly discovered rare-earth triangular-lattice magnet TmMgGaO4. Clear magnetic Bragg peaks at K points are observed in the elastic neutron diffraction measurements. More interesting, however, is the observation of sharp and highly dispersive spin excitations that cannot be explained by a magnetic dipolar order, but instead is the direct consequence of the underlying multipolar order that is "hidden" in the neutron diffraction experiments. We demonstrate that the observed unusual spin correlations and thermodynamics can be accurately described by a transverse field Ising model on the triangular lattice with an intertwined dipolar and ferro-multipolar order.
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Affiliation(s)
- Yao Shen
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, 200433, Shanghai, China
| | - Changle Liu
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, 200433, Shanghai, China
| | - Yayuan Qin
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, 200433, Shanghai, China
| | - Shoudong Shen
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, 200433, Shanghai, China
| | - Yao-Dong Li
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, 200433, Shanghai, China.,Department of Physics, University of California Santa Barbara, Santa Barbara, CA, 93106, USA
| | - Robert Bewley
- ISIS Facility, Rutherford Appleton Laboratory, STFC, Chilton, Didcot, Oxon, OX11 0QX, United Kingdom
| | - Astrid Schneidewind
- Jülich Centre for Neutron Science (JCNS) at Heinz Maier-Leibnitz Zentrum (MLZ), Forschungszentrum Jülich GmbH, Lichtenbergstr. 1, 85748, Garching, Germany
| | - Gang Chen
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, 200433, Shanghai, China. .,Department of Physics and Center of Theoretical and Computational Physics, The University of Hong Kong, Pokfulam Road, Hong Kong, China. .,Center for Field Theory and Particle Physics, Fudan University, 200433, Shanghai, China. .,Collaborative Innovation Center of Advanced Microstructures, Nanjing University, 210093, Nanjing, China.
| | - Jun Zhao
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, 200433, Shanghai, China. .,Collaborative Innovation Center of Advanced Microstructures, Nanjing University, 210093, Nanjing, China.
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52
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Hester G, Nair HS, Reeder T, Yahne DR, DeLazzer TN, Berges L, Ziat D, Neilson JR, Aczel AA, Sala G, Quilliam JA, Ross KA. Novel Strongly Spin-Orbit Coupled Quantum Dimer Magnet: Yb_{2}Si_{2}O_{7}. PHYSICAL REVIEW LETTERS 2019; 123:027201. [PMID: 31386489 DOI: 10.1103/physrevlett.123.027201] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/31/2018] [Indexed: 06/10/2023]
Abstract
The quantum dimer magnet (QDM) is the canonical example of quantum magnetism. The QDM state consists of entangled nearest-neighbor spin dimers and often exhibits a field-induced triplon Bose-Einstein condensate (BEC) phase. We report on a new QDM in the strongly spin-orbit coupled, distorted honeycomb-lattice material Yb_{2}Si_{2}O_{7}. Our single crystal neutron scattering, specific heat, and ultrasound velocity measurements reveal a gapped singlet ground state at zero field with sharp, dispersive excitations. We find a field-induced magnetically ordered phase reminiscent of a BEC phase, with exceptionally low critical fields of H_{c1}∼0.4 and H_{c2}∼1.4 T. Using inelastic neutron scattering in an applied magnetic field we observe a Goldstone mode (gapless to within δE=0.037 meV) that persists throughout the entire field-induced magnetically ordered phase, suggestive of the spontaneous breaking of U(1) symmetry expected for a triplon BEC. However, in contrast to other well-known cases of this phase, the high-field (μ_{0}H≥1.2 T) part of the phase diagram in Yb_{2}Si_{2}O_{7} is interrupted by an unusual regime signaled by a change in the field dependence of the ultrasound velocity and magnetization, as well as the disappearance of a sharp anomaly in the specific heat. These measurements raise the question of how anisotropy in strongly spin-orbit coupled materials modifies the field induced phases of QDMs.
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Affiliation(s)
- Gavin Hester
- Department of Physics, Colorado State University, 200 W. Lake St., Fort Collins, Colorado 80523-1875, USA
| | - H S Nair
- Department of Physics, Colorado State University, 200 W. Lake St., Fort Collins, Colorado 80523-1875, USA
| | - T Reeder
- Department of Physics, Colorado State University, 200 W. Lake St., Fort Collins, Colorado 80523-1875, USA
| | - D R Yahne
- Department of Physics, Colorado State University, 200 W. Lake St., Fort Collins, Colorado 80523-1875, USA
| | - T N DeLazzer
- Department of Physics, Colorado State University, 200 W. Lake St., Fort Collins, Colorado 80523-1875, USA
| | - L Berges
- Institut Quantique and Département de Physique, Université de Sherbrooke, 2500 boulevard de l'Université, Sherbrooke, Québec J1K 2R1, Canada
| | - D Ziat
- Institut Quantique and Département de Physique, Université de Sherbrooke, 2500 boulevard de l'Université, Sherbrooke, Québec J1K 2R1, Canada
| | - J R Neilson
- Department of Chemistry, Colorado State University, 200 W. Lake St., Fort Collins, Colorado 80523-1872, USA
| | - A A Aczel
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - G Sala
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - J A Quilliam
- Institut Quantique and Département de Physique, Université de Sherbrooke, 2500 boulevard de l'Université, Sherbrooke, Québec J1K 2R1, Canada
| | - K A Ross
- Department of Physics, Colorado State University, 200 W. Lake St., Fort Collins, Colorado 80523-1875, USA
- Quantum Materials Program, Canadian Institute for Advanced Research (CIFAR), Toronto, Ontario M5G 1Z8, Canada
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53
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Wo H, Wang Q, Shen Y, Zhang X, Hao Y, Feng Y, Shen S, He Z, Pan B, Wang W, Nakajima K, Ohira-Kawamura S, Steffens P, Boehm M, Schmalzl K, Forrest TR, Matsuda M, Zhao Y, Lynn JW, Yin Z, Zhao J. Coexistence of Ferromagnetic and Stripe-Type Antiferromagnetic Spin Fluctuations in YFe_{2}Ge_{2}. PHYSICAL REVIEW LETTERS 2019; 122:217003. [PMID: 31283313 DOI: 10.1103/physrevlett.122.217003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/06/2018] [Revised: 04/02/2019] [Indexed: 06/09/2023]
Abstract
We report neutron scattering measurements of single-crystalline YFe_{2}Ge_{2} in the normal state, which has the same crystal structure as the 122 family of iron pnictide superconductors. YFe_{2}Ge_{2} does not exhibit long-range magnetic order but exhibits strong spin fluctuations. Like the iron pnictides, YFe_{2}Ge_{2} displays anisotropic stripe-type antiferromagnetic spin fluctuations at (π, 0, π). More interesting, however, is the observation of strong spin fluctuations at the in-plane ferromagnetic wave vector (0, 0, π). These ferromagnetic spin fluctuations are isotropic in the (H, K) plane, whose intensity exceeds that of stripe spin fluctuations. Both the ferromagnetic and stripe spin fluctuations remain gapless down to the lowest measured energies. Our results naturally explain the absence of magnetic order in YFe_{2}Ge_{2} and also imply that the ferromagnetic correlations may be a key ingredient for iron-based materials.
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Affiliation(s)
- Hongliang Wo
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433, China
| | - Qisi Wang
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433, China
| | - Yao Shen
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433, China
| | - Xiaowen Zhang
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433, China
| | - Yiqing Hao
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433, China
| | - Yu Feng
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433, China
| | - Shoudong Shen
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433, China
| | - Zheng He
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433, China
| | - Bingying Pan
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433, China
| | - Wenbin Wang
- Institute of Nanoelectronic Devices and Quantum Computing, Fudan University, Shanghai 200433, China
| | - K Nakajima
- Materials and Life Science Division, J-PARC Center, Tokai, Ibaraki 319-1195, Japan
| | - S Ohira-Kawamura
- Materials and Life Science Division, J-PARC Center, Tokai, Ibaraki 319-1195, Japan
| | - P Steffens
- Institut Laue-Langevin, 71 Avenue des Martyrs, 38042 Grenoble Cedex 9, France
| | - M Boehm
- Institut Laue-Langevin, 71 Avenue des Martyrs, 38042 Grenoble Cedex 9, France
| | - K Schmalzl
- Forschungszentrum Jülich GmbH. Jülich Centre for Neutron Science at ILL, 71 Avenue des Martyrs, 38000 Grenoble, France
| | - T R Forrest
- Diamond Light Source, Harwell Campus, Didcot OX11 0DE, United Kingdom
| | - M Matsuda
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - Yang Zhao
- NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA
- Department of Materials Science and Engineering, University of Maryland, College Park, Maryland 20742, USA
| | - J W Lynn
- NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA
| | - Zhiping Yin
- Department of Physics and Center for Advanced Quantum Studies, Beijing Normal University, Beijing 100875, China
| | - Jun 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
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54
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Cortie D, Casillas-Garcia G, Squires A, Mole R, Wang X, Liu Y, Chen YH, Yu D. Spin-wave propagation in α-Fe 2O 3 nanorods: the effect of confinement and disorder. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2019; 31:184003. [PMID: 30726775 DOI: 10.1088/1361-648x/ab04ca] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Spin-wave excitations in α-Fe2O3 nanorods were directly detected using time-of-flight inelastic neutron spectroscopy. The dispersive magnon features are compared with those in bulk α-Fe2O3 particles at various temperatures to highlight differences in mode intensity and width. The interchanged spectral intensities in the nanorod are a consequence of a suppressed spin orientation, and this is also evident in the neutron diffraction which demonstates that the weak ferromagnetic phase survives to 1.5 K. Transmission electron microscopy shows that the ellipsoidal particles are single-crystalline with a typical length of 300 ± 100 nm and diameter of 60 ± 10 nm. The main magnon features are similar in bulk and nanoforms and can be explained using a model Hamiltonian based on Samuelson and Shirane's classical theory with exchange constants of J 1 = -1.03 meV, J 2 = -0.28 meV, J 3 = 5.12 meV and J 4 = 4.00 meV. Numerical simulations show that two distinct mechanisms may contribute to the magnon line broadening in the nanorods: a distribution of exchange interactions caused by disorder, and a shortened quasiparticle lifetime caused by the scattering of spin waves at surfaces.
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Affiliation(s)
- David Cortie
- ARC Centre of Excellence in Future Low-Energy Electronics Technologies (FLEET), The University of Wollongong, New South Wales 2500, Australia. Institute for Superconducting and Electronic Materials, The University of Wollongong, New South Wales 2500, Australia
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55
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Cheng YQ, Daemen LL, Kolesnikov AI, Ramirez-Cuesta AJ. Simulation of Inelastic Neutron Scattering Spectra Using OCLIMAX. J Chem Theory Comput 2019; 15:1974-1982. [DOI: 10.1021/acs.jctc.8b01250] [Citation(s) in RCA: 66] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Y. Q. Cheng
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge Tennessee 37831, United States
| | - L. L. Daemen
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge Tennessee 37831, United States
| | - A. I. Kolesnikov
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge Tennessee 37831, United States
| | - A. J. Ramirez-Cuesta
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge Tennessee 37831, United States
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56
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Kim K, Lim SY, Lee JU, Lee S, Kim TY, Park K, Jeon GS, Park CH, Park JG, Cheong H. Suppression of magnetic ordering in XXZ-type antiferromagnetic monolayer NiPS 3. Nat Commun 2019; 10:345. [PMID: 30664705 PMCID: PMC6341093 DOI: 10.1038/s41467-018-08284-6] [Citation(s) in RCA: 104] [Impact Index Per Article: 20.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2018] [Accepted: 12/27/2018] [Indexed: 12/24/2022] Open
Abstract
How a certain ground state of complex physical systems emerges, especially in two-dimensional materials, is a fundamental question in condensed-matter physics. A particularly interesting case is systems belonging to the class of XY Hamiltonian where the magnetic order parameter of conventional nature is unstable in two-dimensional materials leading to a Berezinskii-Kosterlitz-Thouless transition. Here, we report how the XXZ-type antiferromagnetic order of a magnetic van der Waals material, NiPS3, behaves upon reducing the thickness and ultimately becomes unstable in the monolayer limit. Our experimental data are consistent with the findings based on renormalization-group theory that at low temperatures a two-dimensional XXZ system behaves like a two-dimensional XY one, which cannot have a long-range order at finite temperatures. This work provides the experimental examination of the XY magnetism in the atomically thin limit and opens opportunities of exploiting these fundamental theorems of magnetism using magnetic van der Waals materials.
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Affiliation(s)
- Kangwon Kim
- Department of Physics, Sogang University, Seoul, 04107, Korea
| | - Soo Yeon Lim
- Department of Physics, Sogang University, Seoul, 04107, Korea
| | - Jae-Ung Lee
- Department of Physics, Sogang University, Seoul, 04107, Korea
| | - Sungmin Lee
- Center for Correlated Electron Systems, Institute for Basic Science, Seoul, 08826, Korea
- Department of Physics and Astronomy, Seoul National University, Seoul, 08826, Korea
| | - Tae Yun Kim
- Department of Physics and Astronomy, Seoul National University, Seoul, 08826, Korea
- Center for Theoretical Physics, Seoul National University, Seoul, 08826, Korea
| | - Kisoo Park
- Center for Correlated Electron Systems, Institute for Basic Science, Seoul, 08826, Korea
- Department of Physics and Astronomy, Seoul National University, Seoul, 08826, Korea
| | - Gun Sang Jeon
- Department of Physics, Ewha Womans University, Seoul, 03760, Korea
| | - Cheol-Hwan Park
- Department of Physics and Astronomy, Seoul National University, Seoul, 08826, Korea.
- Center for Theoretical Physics, Seoul National University, Seoul, 08826, Korea.
| | - Je-Geun Park
- Center for Correlated Electron Systems, Institute for Basic Science, Seoul, 08826, Korea.
- Department of Physics and Astronomy, Seoul National University, Seoul, 08826, Korea.
| | - Hyeonsik Cheong
- Department of Physics, Sogang University, Seoul, 04107, Korea.
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57
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Abstract
Antiferromagnets can host strong quantum fluctuations in their ground state if they combine both low dimensionality and low spin. Materials based on copper oxides (spin-1/2 ions in layered or 1D structures) are unique in optimizing the tendency to strong quantum fluctuations. As a bonus, they show extremely large magnetic interactions, which lead to interesting quantum effects at relatively high temperatures as anomalous transport properties and high-Tc superconductivity in doped systems. Obtaining similar features with other ions has been a long-standing goal. We show that silver and fluorine (which are next to copper and oxygen in the periodic table) in the commercial compound AgF2 reach the goal, paving the way for a different generation of quantum materials. The parent compound of high-Tc superconducting cuprates is a unique Mott insulator consisting of layers of spin-12 ions forming a square lattice and with a record high in-plane antiferromagnetic coupling. Compounds with similar characteristics have long been searched for without success. Here, we use a combination of experimental and theoretical tools to show that commercial AgF2 is an excellent cuprate analog with remarkably similar electronic parameters to La2CuO4 but larger buckling of planes. Two-magnon Raman scattering and inelastic neutron scattering reveal a superexchange constant reaching 70% of that of a typical cuprate. We argue that structures that reduce or eliminate the buckling of the AgF2 planes could have an antiferromagnetic coupling that matches or surpasses the cuprates.
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58
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Matsuda M, Dissanayake SE, Abernathy DL, Qiu Y, Copley JRD, Kumada N, Azuma M. Frustrated magnetic interactions in an S = 3/2 bilayer honeycomb lattice compound Bi 3Mn 4O 12(NO 3). PHYSICAL REVIEW. B 2019; 100:10.1103/physrevb.100.134430. [PMID: 33644522 PMCID: PMC7905988 DOI: 10.1103/physrevb.100.134430] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
An inelastic neutron scattering study has been performed in an S = 3/2 bilayer honeycomb lattice compound Bi3Mn4O12(NO3) at ambient and high magnetic fields. Relatively broad and monotonically dispersive magnetic excitations were observed at ambient field, where no long-range magnetic order exists. In the magnetic-field-induced long-range ordered state at 10 T, the magnetic dispersions become slightly more intense, albeit still broad as in the disordered state, and two excitation gaps, probably originating from an easy-plane magnetic anisotropy and intrabilayer interactions, develop. Analyzing the magnetic dispersions using the linear spin-wave theory, we estimated the intraplane and intrabilayer magnetic interactions, which are almost consistent with those determined by ab initio density functional theory calculations [M. Alaei et al., Phys. Rev. B 96, 140404(R) (2017)], except the third and fourth neighbor intrabilayer interactions. Most importantly, as predicted by the theory, there is no significant frustration in the honeycomb plane but frustrating intrabilayer interactions probably give rise to the disordered ground state.
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Affiliation(s)
- M Matsuda
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - S E Dissanayake
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - D L Abernathy
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - Y Qiu
- NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA
| | - J R D Copley
- NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA
| | - N Kumada
- Center for Crystal Science and Technology, University of Yamanashi, 7-32 Miyamae, Kofu 400-8511, Japan
| | - M Azuma
- Laboratory for Materials and Structures, Tokyo Institute of Technology, 4259 Nagatsuta, Midori, Yokohama 226-8503, Japan
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59
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Bettler S, Landolt F, Aksoy ÖM, Yan Z, Gvasaliya S, Qiu Y, Ressouche E, Beauvois K, Raymond S, Ponomaryov AN, Zvyagin SA, Zheludev A. Magnetic structure and spin waves in the frustrated ferro-antiferromagnet Pb 2VO(PO 4) 2. PHYSICAL REVIEW. B 2019; 99:10.1103/physrevb.99.184437. [PMID: 32118124 PMCID: PMC7047833 DOI: 10.1103/physrevb.99.184437] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Single crystal neutron diffraction, inelastic neutron scattering, and electron spin resonance experiments are used to study the magnetic structure and spin waves in Pb2VO(PO4)2, a prototypical layered S = 1/2 ferromagnet with frustrating next-nearest neighbor antiferromagnetic interactions. The observed excitation spectrum is found to be inconsistent with a simple square lattice model previously proposed for this material. At least four distinct exchange coupling constants are required to reproduce the measured spin wave dispersion. The degree of magnetic frustration is correspondingly revised and found to be substantially smaller than in all previous estimates.
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Affiliation(s)
- S. Bettler
- Laboratory for Solid State Physics, ETH Zürich, 8093 Zürich, Switzerland
| | - F. Landolt
- Laboratory for Solid State Physics, ETH Zürich, 8093 Zürich, Switzerland
| | - Ö. M. Aksoy
- Laboratory for Solid State Physics, ETH Zürich, 8093 Zürich, Switzerland
| | - Z. Yan
- Laboratory for Solid State Physics, ETH Zürich, 8093 Zürich, Switzerland
| | - S. Gvasaliya
- Laboratory for Solid State Physics, ETH Zürich, 8093 Zürich, Switzerland
| | - Y. Qiu
- NIST Centre for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20878, USA
| | - E. Ressouche
- Univ. Grenoble Alpes, CEA, INAC-MEM, 38000 Grenoble, France
| | - K. Beauvois
- Univ. Grenoble Alpes, CEA, INAC-MEM, 38000 Grenoble, France
| | - S. Raymond
- Univ. Grenoble Alpes, CEA, INAC-MEM, 38000 Grenoble, France
| | - A. N. Ponomaryov
- Dresden High Magnetic Field Laboratory (HLD-EMFL), Helmholtz-Zentrum Dresden-Rossendorf, 01328 Dresden, Germany
| | - S. A. Zvyagin
- Dresden High Magnetic Field Laboratory (HLD-EMFL), Helmholtz-Zentrum Dresden-Rossendorf, 01328 Dresden, Germany
| | - A. Zheludev
- Laboratory for Solid State Physics, ETH Zürich, 8093 Zürich, Switzerland
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60
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Boldrin D, Fåk B, Canévet E, Ollivier J, Walker HC, Manuel P, Khalyavin DD, Wills AS. Vesignieite: An S=1/2 Kagome Antiferromagnet with Dominant Third-Neighbor Exchange. PHYSICAL REVIEW LETTERS 2018; 121:107203. [PMID: 30240241 DOI: 10.1103/physrevlett.121.107203] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/01/2018] [Indexed: 06/08/2023]
Abstract
The spin-1/2 kagome antiferromagnet is an archetypal frustrated system predicted to host a variety of exotic magnetic states. We show using neutron scattering measurements that deuterated vesignieite BaCu_{3}V_{2}O_{8}(OD)_{2}, a fully stoichiometric S=1/2 kagome magnet with <1% lattice distortion, orders magnetically at T_{N}=9 K into a multi-k coplanar variant of the predicted triple-k octahedral structure. We find that this structure is stabilized by a dominant antiferromagnetic third-neighbor exchange J_{3} with minor first- or second-neighbor exchanges. The spin-wave spectrum is well described by a J_{3}-only model including a tiny symmetric exchange anisotropy.
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Affiliation(s)
- D Boldrin
- Department of Chemistry, University College London, 20 Gordon Street, London, WC1H 0AJ, United Kingdom
| | - B Fåk
- Institut Laue-Langevin, 71 avenue des Martyrs, CS 20156, 38042 Grenoble Cedex 9, France
| | - E Canévet
- Institut Laue-Langevin, 71 avenue des Martyrs, CS 20156, 38042 Grenoble Cedex 9, France
- Laboratoire de Physique des Solides, CNRS, Université Paris-Sud, Université Paris-Saclay, 91405 Orsay Cedex, France
| | - J Ollivier
- Institut Laue-Langevin, 71 avenue des Martyrs, CS 20156, 38042 Grenoble Cedex 9, France
| | - H C Walker
- STFC Rutherford Appleton Lab, ISIS Facility, Harwell Science and Innovation Campus, Didcot, OX11 0QX, United Kingdom
| | - P Manuel
- STFC Rutherford Appleton Lab, ISIS Facility, Harwell Science and Innovation Campus, Didcot, OX11 0QX, United Kingdom
| | - D D Khalyavin
- STFC Rutherford Appleton Lab, ISIS Facility, Harwell Science and Innovation Campus, Didcot, OX11 0QX, United Kingdom
| | - A S Wills
- Department of Chemistry, University College London, 20 Gordon Street, London, WC1H 0AJ, United Kingdom
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61
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Park K, Sim H, Leiner JC, Yoshida Y, Jeong J, Yano SI, Gardner J, Bourges P, Klicpera M, Sechovský V, Boehm M, Park JG. Low-energy spin dynamics of orthoferrites AFeO 3 (A = Y, La, Bi). JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2018; 30:235802. [PMID: 29697406 DOI: 10.1088/1361-648x/aac06b] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
YFeO3 and LaFeO3 are members of the rare-earth orthoferrites family with Pbnm space group. Using inelastic neutron scattering, the low-energy spin excitations have been measured around the magnetic Brillouin zone center. Splitting of magnon branches and finite magnon gaps (∼2 meV) are observed for both compounds, where the Dzyaloshinsky-Moriya interactions account for most of this gap with some additional contribution from single-ion anisotropy. We also make comparisons with multiferroic BiFeO3 (R3c space group), in which similar behavior was observed. By taking into account all relevant local Dzyaloshinsky-Moriya interactions, our analysis allows for the precise determination of all experimentally observed parameters in the spin-Hamiltonian. We find that different properties of the Pbnm and R3c space group lead to the stabilization of a spin cycloid structure in the latter case but not in the former, which explains the difference in the levels of complexity of magnon band structures for the respective compounds.
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Affiliation(s)
- Kisoo Park
- Center for Correlated Electron Systems, Institute for Basic Science (IBS), Seoul 08826, Republic of Korea. Department of Physics and Astronomy, Seoul National University, Seoul 08826, Republic of Korea
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62
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Amplitude mode in the planar triangular antiferromagnet Na 0.9MnO 2. Nat Commun 2018; 9:2188. [PMID: 29872040 PMCID: PMC5988795 DOI: 10.1038/s41467-018-04601-1] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2017] [Accepted: 05/11/2018] [Indexed: 11/11/2022] Open
Abstract
Amplitude modes arising from symmetry breaking in materials are of broad interest in condensed matter physics. These modes reflect an oscillation in the amplitude of a complex order parameter, yet are typically unstable and decay into oscillations of the order parameter’s phase. This renders stable amplitude modes rare, and exotic effects in quantum antiferromagnets have historically provided a realm for their detection. Here we report an alternate route to realizing amplitude modes in magnetic materials by demonstrating that an antiferromagnet on a two-dimensional anisotropic triangular lattice (α-Na0.9MnO2) exhibits a long-lived, coherent oscillation of its staggered magnetization field. Our results show that geometric frustration of Heisenberg spins with uniaxial single-ion anisotropy can renormalize the interactions of a dense two-dimensional network of moments into largely decoupled, one-dimensional chains that manifest a longitudinally polarized-bound state. This bound state is driven by the Ising-like anisotropy inherent to the Mn3+ ions of this compound. Oscillations of the order parameter amplitude in magnetically ordered materials provide condensed matter analogues of the Higgs boson but in most cases they are unstable. Dally et al. show that the quasi-one-dimensional magnet α-Na0.9MnO2 supports stable amplitude excitations.
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63
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Rule KC, Mole RA, Zanardo J, Krause-Heuer A, Darwish T, Lerch M, Yu D. Measuring the excitations in a new S = 1/2 quantum spin chain material with competing interactions. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2018; 30:215602. [PMID: 29651987 DOI: 10.1088/1361-648x/aabdf9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Recently a new one-dimensional (1D) quantum spin chain system has been reported: catena-dichloro(2-Cl-3Mpy)copper(II), (where 2-Cl-3Mpy=2-chloro-3-methylpyridine). Preliminary calculations and bulk magnetic property measurements indicate that this system does not undergo magnetic ordering down to 1.8 K and is a prime candidate for investigating frustration in a J 1/J 2 system (where the nearest neighbour interactions, J 1, are ferromagnetic and the next nearest neighbour interactions, J 2, are antiferromagnetic). Calculations predicted three possible magnetic interaction strengths for J 1 below 6 meV depending on the orientation of the ligand. For one of the predicted J 1 values, the existence of a quantum critical point is implied. A deuterated sample of catena-dichloro(2-Cl-3Mpy)copper(II) was synthesised and the excitations measured using inelastic neutron scattering. Scattering indicated the most likely scenario involves spin-chains where each chain consists of only one of the three possible magnetic excitations in this material, rather than the completely random array of exchange interactions within each chain as predicted by Herringer et al (2014 Chem. Eur. J. 20 8355-62). This indicates the possibility of tuning the chemical structure to favour a system which may exhibit a quantum critical point.
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Affiliation(s)
- K C Rule
- Australian Nuclear Science and Technology Organisation, Locked bag 2001, Kirrawee DC, NSW 2232, Australia. School of Physics, Northfields Ave, University of Wollongong, NSW 2522, Australia
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64
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Ma Z, Wang J, Dong ZY, Zhang J, Li S, Zheng SH, Yu Y, Wang W, Che L, Ran K, Bao S, Cai Z, Čermák P, Schneidewind A, Yano S, Gardner JS, Lu X, Yu SL, Liu JM, Li S, Li JX, Wen J. Spin-Glass Ground State in a Triangular-Lattice Compound YbZnGaO_{4}. PHYSICAL REVIEW LETTERS 2018. [PMID: 29543015 DOI: 10.1103/physrevlett.120.087201] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
We report on comprehensive results identifying the ground state of a triangular-lattice structured YbZnGaO_{4} as a spin glass, including no long-range magnetic order, prominent broad excitation continua, and the absence of magnetic thermal conductivity. More crucially, from the ultralow-temperature ac susceptibility measurements, we unambiguously observe frequency-dependent peaks around 0.1 K, indicating the spin-glass ground state. We suggest this conclusion holds also for its sister compound YbMgGaO_{4}, which is confirmed by the observation of spin freezing at low temperatures. We consider disorder and frustration to be the main driving force for the spin-glass phase.
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Affiliation(s)
- Zhen Ma
- National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, Nanjing 210093, China
| | - Jinghui Wang
- National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, Nanjing 210093, China
| | - Zhao-Yang Dong
- National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, Nanjing 210093, China
| | - Jun Zhang
- State Key Laboratory of Surface Physics, Department of Physics, and Laboratory of Advanced Materials, Fudan University, Shanghai 200433, China
| | - Shichao Li
- National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, Nanjing 210093, China
| | - Shu-Han Zheng
- National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, Nanjing 210093, China
| | - Yunjie Yu
- State Key Laboratory of Surface Physics, Department of Physics, and Laboratory of Advanced Materials, Fudan University, Shanghai 200433, China
| | - Wei Wang
- National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, Nanjing 210093, China
| | - Liqiang Che
- Center for Correlated Matter and Department of Physics, Zhejiang University, Hangzhou 310058, China
| | - Kejing Ran
- National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, Nanjing 210093, China
| | - Song Bao
- National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, Nanjing 210093, China
| | - Zhengwei Cai
- National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, Nanjing 210093, China
| | - P Čermák
- Jülich Centre for Neutron Science (JCNS) at Heinz Maier-Leibnitz Zentrum (MLZ), Forschungszentrum Jülich GmbH, Lichtenbergstr. 1, 85748 Garching, Germany
| | - A Schneidewind
- Jülich Centre for Neutron Science (JCNS) at Heinz Maier-Leibnitz Zentrum (MLZ), Forschungszentrum Jülich GmbH, Lichtenbergstr. 1, 85748 Garching, Germany
| | - S Yano
- National Synchrotron Radiation Research Center, Hsinchu 30077, Taiwan
| | - J S Gardner
- National Synchrotron Radiation Research Center, Hsinchu 30077, Taiwan
- Center for Condensed Matter Sciences, National Taiwan University, Taipei 10617, Taiwan
| | - Xin Lu
- Center for Correlated Matter and Department of Physics, Zhejiang University, Hangzhou 310058, China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
| | - Shun-Li Yu
- National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, Nanjing 210093, China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
| | - Jun-Ming Liu
- National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, Nanjing 210093, China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
| | - Shiyan Li
- State Key Laboratory of Surface Physics, Department of Physics, and Laboratory of Advanced Materials, Fudan University, Shanghai 200433, China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
| | - Jian-Xin Li
- National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, Nanjing 210093, China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
| | - Jinsheng Wen
- National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, Nanjing 210093, China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
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65
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Cemal E, Enderle M, Kremer RK, Fåk B, Ressouche E, Goff JP, Gvozdikova MV, Zhitomirsky ME, Ziman T. Field-induced States and Excitations in the Quasicritical Spin-1/2 Chain Linarite. PHYSICAL REVIEW LETTERS 2018; 120:067203. [PMID: 29481234 DOI: 10.1103/physrevlett.120.067203] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/25/2017] [Indexed: 06/08/2023]
Abstract
The mineral linarite, PbCuSO_{4}(OH)_{2}, is a spin-1/2 chain with frustrating nearest-neighbor ferromagnetic and next-nearest-neighbor antiferromagnetic exchange interactions. Our inelastic neutron scattering experiments performed above the saturation field establish that the ratio between these exchanges is such that linarite is extremely close to the quantum critical point between spin-multipolar phases and the ferromagnetic state. We show that the predicted quantum multipolar phases are fragile and actually suppressed by a tiny orthorhombic exchange anisotropy and weak interchain interactions in favor of a dipolar fan phase. Including this anisotropy in classical simulations of a nearly critical model explains the field-dependent phase sequence of the phase diagram of linarite, its strong dependence of the magnetic field direction, and the measured variations of the wave vector as well as the staggered and the uniform magnetizations in an applied field.
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Affiliation(s)
- Eron Cemal
- Institut Laue-Langevin, CS 20156, 38042 Grenoble Cedex 9, France
- Royal Holloway, University of London, Egham, Surrey TW20 0EX, United Kingdom
| | | | - Reinhard K Kremer
- Max-Planck Institute for Solid State Research, Heisenbergstrasse 1, 70569 Stuttgart, Germany
| | - Björn Fåk
- Institut Laue-Langevin, CS 20156, 38042 Grenoble Cedex 9, France
| | - Eric Ressouche
- Université Grenoble Alpes, CEA, INAC, MEM F-38000 Grenoble, France
| | - Jon P Goff
- Royal Holloway, University of London, Egham, Surrey TW20 0EX, United Kingdom
| | | | | | - Tim Ziman
- Institut Laue-Langevin, CS 20156, 38042 Grenoble Cedex 9, France
- LPMMC, UMR-5493, Université Grenoble Alpes and CNRS, 38042 Grenoble, France
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66
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Hallas AM, Gaudet J, Butch NP, Xu G, Tachibana M, Wiebe CR, Luke GM, Gaulin BD. Phase Competition in the Palmer-Chalker XY Pyrochlore Er_{2}Pt_{2}O_{7}. PHYSICAL REVIEW LETTERS 2017; 119:187201. [PMID: 29219594 DOI: 10.1103/physrevlett.119.187201] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/18/2017] [Indexed: 06/07/2023]
Abstract
We report neutron scattering measurements on Er_{2}Pt_{2}O_{7}, a new addition to the XY family of frustrated pyrochlore magnets. Symmetry analysis of our elastic scattering data shows that Er_{2}Pt_{2}O_{7} orders into the k=0, Γ_{7} magnetic structure (the Palmer-Chalker state), at T_{N}=0.38 K. This contrasts with its sister XY pyrochlore antiferromagnets Er_{2}Ti_{2}O_{7} and Er_{2}Ge_{2}O_{7}, both of which order into Γ_{5} magnetic structures at much higher temperatures, T_{N}=1.2 and 1.4 K, respectively. In this temperature range, the magnetic heat capacity of Er_{2}Pt_{2}O_{7} contains a broad anomaly centered at T^{*}=1.5 K. Our inelastic neutron scattering measurements reveal that this broad heat capacity anomaly sets the temperature scale for strong short-range spin fluctuations. Below T_{N}=0.38 K, Er_{2}Pt_{2}O_{7} displays a gapped spin-wave spectrum with an intense, flat band of excitations at lower energy and a weak, diffusive band of excitations at higher energy. The flat band is well described by classical spin-wave calculations, but these calculations also predict sharp dispersive branches at higher energy, a striking discrepancy with the experimental data. This, in concert with the strong suppression of T_{N}, is attributable to enhanced quantum fluctuations due to phase competition between the Γ_{7} and Γ_{5} states that border each other within a classically predicted phase diagram.
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Affiliation(s)
- A M Hallas
- Department of Physics and Astronomy, McMaster University, Hamilton, Ontario L8S 4M1, Canada
| | - J Gaudet
- Department of Physics and Astronomy, McMaster University, Hamilton, Ontario L8S 4M1, Canada
| | - N P Butch
- Center for Neutron Research, National Institute of Standards and Technology, 100 Bureau Drive, MS 6100, Gaithersburg, Maryland 20899, USA
| | - Guangyong Xu
- Center for Neutron Research, National Institute of Standards and Technology, 100 Bureau Drive, MS 6100, Gaithersburg, Maryland 20899, USA
| | - M Tachibana
- National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Ibaraki, Japan
| | - C R Wiebe
- Department of Physics and Astronomy, McMaster University, Hamilton, Ontario L8S 4M1, Canada
- Department of Chemistry, University of Winnipeg, Winnipeg, Manitoba R3B 2E9, Canada
- Canadian Institute for Advanced Research, 661 University Avenue, Toronto, Ontario M5G 1M1, Canada
| | - G M Luke
- Department of Physics and Astronomy, McMaster University, Hamilton, Ontario L8S 4M1, Canada
- Canadian Institute for Advanced Research, 661 University Avenue, Toronto, Ontario M5G 1M1, Canada
| | - B D Gaulin
- Department of Physics and Astronomy, McMaster University, Hamilton, Ontario L8S 4M1, Canada
- Canadian Institute for Advanced Research, 661 University Avenue, Toronto, Ontario M5G 1M1, Canada
- Brockhouse Institute for Materials Research, Hamilton, Ontario L8S 4M1, Canada
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67
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Winter SM, Riedl K, Maksimov PA, Chernyshev AL, Honecker A, Valentí R. Breakdown of magnons in a strongly spin-orbital coupled magnet. Nat Commun 2017; 8:1152. [PMID: 29074965 PMCID: PMC5658390 DOI: 10.1038/s41467-017-01177-0] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2017] [Accepted: 08/24/2017] [Indexed: 11/09/2022] Open
Abstract
The description of quantized collective excitations stands as a landmark in the quantum theory of condensed matter. A prominent example occurs in conventional magnets, which support bosonic magnons-quantized harmonic fluctuations of the ordered spins. In striking contrast is the recent discovery that strongly spin-orbital-coupled magnets, such as α-RuCl3, may display a broad excitation continuum inconsistent with conventional magnons. Due to incomplete knowledge of the underlying interactions unraveling the nature of this continuum remains challenging. The most discussed explanation refers to a coherent continuum of fractional excitations analogous to the celebrated Kitaev spin liquid. Here, we present a more general scenario. We propose that the observed continuum represents incoherent excitations originating from strong magnetic anharmonicity that naturally occurs in such materials. This scenario fully explains the observed inelastic magnetic response of α-RuCl3 and reveals the presence of nontrivial excitations in such materials extending well beyond the Kitaev state.
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Affiliation(s)
- Stephen M Winter
- Institut für Theoretische Physik, Goethe-Universität Frankfurt, Max-von-Laue-Strasse 1, 60438, Frankfurt am Main, Germany.
| | - Kira Riedl
- Institut für Theoretische Physik, Goethe-Universität Frankfurt, Max-von-Laue-Strasse 1, 60438, Frankfurt am Main, Germany
| | - Pavel A Maksimov
- Department of Physics and Astronomy, University of California, Irvine, CA, 92697, USA
| | | | - Andreas Honecker
- Laboratoire de Physique Théorique et Modélisation, CNRS UMR 8089, Université de Cergy-Pontoise, 95302, Cergy-Pontoise Cedex, France
| | - Roser Valentí
- Institut für Theoretische Physik, Goethe-Universität Frankfurt, Max-von-Laue-Strasse 1, 60438, Frankfurt am Main, Germany
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68
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Mole RA, Greene S, Henry PF, Humphrey SM, Rule KC, Unruh T, Weldon GF, Yu D, Stride JA, Wood PT. Magnetic Properties of the Distorted Kagomé Lattice Mn 3(1,2,4-(O 2C) 3C 6H 3) 2. Inorg Chem 2017. [DOI: 10.1021/acs.inorgchem.7b00597] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Richard A. Mole
- Australian Nuclear Science and Technology Organisation, Locked Bag 2001, Kirrawee
DC, NSW 2225, Australia
- Department
of Chemistry, University of New South Wales, Sydney, NSW 2052, Australia
| | - Stephen Greene
- Department
of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, U.K
| | - Paul F. Henry
- Institut Laue-Langevin, CS 20156, F-38042 Grenoble Cedex 9, France
- The
ISIS
Facility, STFC Rutherford Appleton Laboratory, Harwell Campus, Didcot OX11 0QX, U.K
| | - Simon M. Humphrey
- Department
of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, U.K
- Department
of Chemistry, University of Texas at Austin, Welch Hall 2.204, 105E. 24th Street
A5300, Austin, Texas 78712-1224, United States
| | - Kirrily C. Rule
- Australian Nuclear Science and Technology Organisation, Locked Bag 2001, Kirrawee
DC, NSW 2225, Australia
| | - Tobias Unruh
- Heinz
Maier Leibnitz Zenturm, Technische Universitaet Muenchen, Lichtenbergstrasse
1, Garching 85747, Germany
- Chair
for Crystallography and Structural Physics, Physics Department, University of Erlangen-Nürnberg, 91058 Erlangen, Germany
| | - Gerald F. Weldon
- Department
of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, U.K
| | - Dehong Yu
- Australian Nuclear Science and Technology Organisation, Locked Bag 2001, Kirrawee
DC, NSW 2225, Australia
| | - John A. Stride
- Australian Nuclear Science and Technology Organisation, Locked Bag 2001, Kirrawee
DC, NSW 2225, Australia
- Department
of Chemistry, University of New South Wales, Sydney, NSW 2052, Australia
| | - Paul T. Wood
- Department
of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, U.K
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69
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Li Y, Adroja D, Voneshen D, Bewley RI, Zhang Q, Tsirlin AA, Gegenwart P. Nearest-neighbour resonating valence bonds in YbMgGaO 4. Nat Commun 2017. [PMID: 28639624 PMCID: PMC5489678 DOI: 10.1038/ncomms15814] [Citation(s) in RCA: 47] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Since its proposal by Anderson, resonating valence bonds (RVB) formed by a superposition of fluctuating singlet pairs have been a paradigmatic concept in understanding quantum spin liquids. Here, we show that excitations related to singlet breaking on nearest-neighbour bonds describe the high-energy part of the excitation spectrum in YbMgGaO4, the effective spin-1/2 frustrated antiferromagnet on the triangular lattice, as originally considered by Anderson. By a thorough single-crystal inelastic neutron scattering study, we demonstrate that nearest-neighbour RVB excitations account for the bulk of the spectral weight above 0.5 meV. This renders YbMgGaO4 the first experimental system where putative RVB correlations restricted to nearest neighbours are observed, and poses a fundamental question of how complex interactions on the triangular lattice conspire to form this unique many-body state. The signature of short range resonating valence bonds (RVB) to understand quantum spin liquids is yet to be explored. Here, Li et al. observe the putative RVB correlations restricted to nearest neighbours in YbMgGaO4, responsible for the high-energy spin excitations.
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Affiliation(s)
- Yuesheng Li
- Experimental Physics VI, Center for Electronic Correlations and Magnetism, University of Augsburg, 86159 Augsburg, Germany.,Department of Physics, Renmin University of China, Beijing 100872, China
| | - Devashibhai Adroja
- ISIS Pulsed Neutron and Muon Source, STFC Rutherford Appleton Laboratory, Harwell Campus, Didcot, Oxfordshire OX11 0QX, UK.,Highly Correlated Matter Research Group, Physics Department, University of Johannesburg, PO Box 524, Auckland Park 2006, South Africa
| | - David Voneshen
- ISIS Pulsed Neutron and Muon Source, STFC Rutherford Appleton Laboratory, Harwell Campus, Didcot, Oxfordshire OX11 0QX, UK
| | - Robert I Bewley
- ISIS Pulsed Neutron and Muon Source, STFC Rutherford Appleton Laboratory, Harwell Campus, Didcot, Oxfordshire OX11 0QX, UK
| | - Qingming Zhang
- Department of Physics, Renmin University of China, Beijing 100872, China.,Department of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240, China.,Collaborative Innovation Center of Advanced Microstructures, Nanjing 210093, China
| | - Alexander A Tsirlin
- Experimental Physics VI, Center for Electronic Correlations and Magnetism, University of Augsburg, 86159 Augsburg, Germany
| | - Philipp Gegenwart
- Experimental Physics VI, Center for Electronic Correlations and Magnetism, University of Augsburg, 86159 Augsburg, Germany
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70
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Banerjee A, Yan J, Knolle J, Bridges CA, Stone MB, Lumsden MD, Mandrus DG, Tennant DA, Moessner R, Nagler SE. Neutron scattering in the proximate quantum spin liquid α-RuCl
3. Science 2017; 356:1055-1059. [DOI: 10.1126/science.aah6015] [Citation(s) in RCA: 395] [Impact Index Per Article: 56.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2016] [Accepted: 05/16/2017] [Indexed: 01/30/2023]
Affiliation(s)
- Arnab Banerjee
- Quantum Condensed Matter Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
| | - Jiaqiang Yan
- Material Sciences and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
| | - Johannes Knolle
- Department of Physics, Cavendish Laboratory, JJ Thomson Avenue, Cambridge CB3 0HE, UK
| | - Craig A. Bridges
- Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
| | - Matthew B. Stone
- Quantum Condensed Matter Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
| | - Mark D. Lumsden
- Quantum Condensed Matter Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
| | - David G. Mandrus
- Material Sciences and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
- Department of Materials Science and Engineering, University of Tennesee, Knoxville, TN 37996, USA
| | - David A. Tennant
- Neutron Sciences Directorate, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
| | - Roderich Moessner
- Max Planck Institute for the Physics of Complex Systems, D-01187 Dresden, Germany
| | - Stephen E. Nagler
- Quantum Condensed Matter Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
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71
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Hong T, Qiu Y, Matsumoto M, Tennant DA, Coester K, Schmidt KP, Awwadi FF, Turnbull MM, Agrawal H, Chernyshev AL. Field induced spontaneous quasiparticle decay and renormalization of quasiparticle dispersion in a quantum antiferromagnet. Nat Commun 2017; 8:15148. [PMID: 28474679 PMCID: PMC5424150 DOI: 10.1038/ncomms15148] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2016] [Accepted: 03/02/2017] [Indexed: 11/09/2022] Open
Abstract
The notion of a quasiparticle, such as a phonon, a roton or a magnon, is used in modern condensed matter physics to describe an elementary collective excitation. The intrinsic zero-temperature magnon damping in quantum spin systems can be driven by the interaction of the one-magnon states and multi-magnon continuum. However, detailed experimental studies on this quantum many-body effect induced by an applied magnetic field are rare. Here we present a high-resolution neutron scattering study in high fields on an S=1/2 antiferromagnet C9H18N2CuBr4. Compared with the non-interacting linear spin–wave theory, our results demonstrate a variety of phenomena including field-induced renormalization of one-magnon dispersion, spontaneous magnon decay observed via intrinsic linewidth broadening, unusual non-Lorentzian two-peak structure in the excitation spectra and a dramatic shift of spectral weight from one-magnon state to the two-magnon continuum. Spontaneous magnon decay in canted antiferromagnets has been theoretically investigated extensively, but experimental evidence is limited. Here the authors study the spin ½ antiferromagnet DLCB via neutron scattering, revealing field-induced spontaneous magnon decay associated with three-magnon interactions.
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Affiliation(s)
- Tao Hong
- Quantum Condensed Matter Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - Y Qiu
- National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA
| | - M Matsumoto
- Department of Physics, Shizuoka University, Shizuoka 422-8529, Japan
| | - D A Tennant
- Quantum Condensed Matter Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - K Coester
- Lehrstuhl für Theoretische Physik I, TU Dortmund, D-44221 Dortmund, Germany
| | - K P Schmidt
- Lehrstuhl für Theoretische Physik I, Staudtstrasse 7, Universität Erlangen-Nürnberg, D-91058 Erlangen, Germany
| | - F F Awwadi
- Department of Chemistry, The University of Jordan, Amman 11942, Jordan
| | - M M Turnbull
- Carlson School of Chemistry and Biochemistry, Clark University, Worcester, Massachusetts 01610, USA
| | - H Agrawal
- Instrument and Source Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - A L Chernyshev
- Department of Physics and Astronomy, University of California, Irvine, California 92697, USA
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72
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Li Y, Adroja D, Bewley RI, Voneshen D, Tsirlin AA, Gegenwart P, Zhang Q. Crystalline Electric-Field Randomness in the Triangular Lattice Spin-Liquid YbMgGaO_{4}. PHYSICAL REVIEW LETTERS 2017; 118:107202. [PMID: 28339219 DOI: 10.1103/physrevlett.118.107202] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/04/2016] [Indexed: 06/06/2023]
Abstract
We apply moderate-high-energy inelastic neutron scattering (INS) measurements to investigate Yb^{3+} crystalline electric field (CEF) levels in the triangular spin-liquid candidate YbMgGaO_{4}. Three CEF excitations from the ground-state Kramers doublet are centered at the energies ℏω=39, 61, and 97 meV in agreement with the effective spin-1/2 g factors and experimental heat capacity, but reveal sizable broadening. We argue that this broadening originates from the site mixing between Mg^{2+} and Ga^{3+} giving rise to a distribution of Yb-O distances and orientations and, thus, of CEF parameters that account for the peculiar energy profile of the CEF excitations. The CEF randomness gives rise to a distribution of the effective spin-1/2 g factors and explains the unprecedented broadening of low-energy magnetic excitations in the fully polarized ferromagnetic phase of YbMgGaO_{4}, although a distribution of magnetic couplings due to the Mg/Ga disorder may be important as well.
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Affiliation(s)
- Yuesheng Li
- Department of Physics, Renmin University of China, Beijing 100872, People's Republic of China
- Experimental Physics VI, Center for Electronic Correlations and Magnetism, University of Augsburg, 86159 Augsburg, Germany
| | - Devashibhai Adroja
- ISIS Pulsed Neutron and Muon Source, STFC Rutherford Appleton Laboratory, Harwell Campus, Didcot, Oxfordshire, OX11 0QX, United Kingdom
- Highly Correlated Matter Research Group, Physics Department, University of Johannesburg, PO Box 524, Auckland Park 2006, South Africa
| | - Robert I Bewley
- ISIS Pulsed Neutron and Muon Source, STFC Rutherford Appleton Laboratory, Harwell Campus, Didcot, Oxfordshire, OX11 0QX, United Kingdom
| | - David Voneshen
- ISIS Pulsed Neutron and Muon Source, STFC Rutherford Appleton Laboratory, Harwell Campus, Didcot, Oxfordshire, OX11 0QX, United Kingdom
| | - Alexander A Tsirlin
- Experimental Physics VI, Center for Electronic Correlations and Magnetism, University of Augsburg, 86159 Augsburg, Germany
| | - Philipp Gegenwart
- Experimental Physics VI, Center for Electronic Correlations and Magnetism, University of Augsburg, 86159 Augsburg, Germany
| | - Qingming Zhang
- Department of Physics, Renmin University of China, Beijing 100872, People's Republic of China
- Department of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240, People's Republic of China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing 210093, People's Republic of China
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73
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Tóth S, Wehinger B, Rolfs K, Birol T, Stuhr U, Takatsu H, Kimura K, Kimura T, Rønnow HM, Rüegg C. Electromagnon dispersion probed by inelastic X-ray scattering in LiCrO 2. Nat Commun 2016; 7:13547. [PMID: 27882928 PMCID: PMC5123047 DOI: 10.1038/ncomms13547] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2016] [Accepted: 10/12/2016] [Indexed: 11/30/2022] Open
Abstract
Inelastic X-ray scattering with meV energy resolution (IXS) is an ideal tool to measure collective excitations in solids and liquids. In non-resonant scattering condition, the cross-section is strongly dominated by lattice vibrations (phonons). However, it is possible to probe additional degrees of freedom such as magnetic fluctuations that are strongly coupled to the phonons. The IXS spectrum of the coupled system contains not only the phonon dispersion but also the so far undetected magnetic correlation function. Here we report the observation of strong magnon–phonon coupling in LiCrO2 that enables the measurement of magnetic correlations throughout the Brillouin zone via IXS. We find electromagnon excitations and electric dipole active two-magnon excitations in the magnetically ordered phase and heavily damped electromagnons in the paramagnetic phase of LiCrO2. We predict that several (frustrated) magnets with dominant direct exchange and non-collinear magnetism show surprisingly large IXS cross-section for magnons and multi-magnon processes. Whilst terahertz optical spectroscopy allows for the study of coupled spin and lattice excitations, it is limited in momentum space. Here, the authors use inelastic x-ray scattering to demonstrate strong magnon-phonon coupling and electromagnon excitations across the Brillouin zone of LiCrO2.
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Affiliation(s)
- Sándor Tóth
- Laboratory for Neutron Scattering and Imaging, Paul Scherrer Institute, 5232 Villigen, Switzerland.,Laboratory for Quantum Magnetism, Institute of Physics, EPFL, 1015 Lausanne, Switzerland
| | - Björn Wehinger
- Laboratory for Neutron Scattering and Imaging, Paul Scherrer Institute, 5232 Villigen, Switzerland.,Department of Quantum Matter Physics, University of Geneva, 1211 Genève, Switzerland
| | - Katharina Rolfs
- Laboratory for Scientific Developments and Novel Materials, Paul Scherrer Institute, 5232 Villigen, Switzerland
| | - Turan Birol
- Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota 55455, USA.,Department of Physics and Astronomy, Rutgers University, Piscataway, New Jersey 08854, USA
| | - Uwe Stuhr
- Laboratory for Neutron Scattering and Imaging, Paul Scherrer Institute, 5232 Villigen, Switzerland
| | - Hiroshi Takatsu
- Department of Energy and Hydrocarbon Chemistry, Graduate School of Engineering, Kyoto University, Kyoto 615-8510, Japan.,Department of Physics, Tokyo Metropolitan University, Tokyo 192-0397, Japan
| | - Kenta Kimura
- Division of Materials Physics, Graduate School of Engineering Science, Osaka University, Osaka 560-8531, Japan
| | - Tsuyoshi Kimura
- Division of Materials Physics, Graduate School of Engineering Science, Osaka University, Osaka 560-8531, Japan
| | - Henrik M Rønnow
- Laboratory for Quantum Magnetism, Institute of Physics, EPFL, 1015 Lausanne, Switzerland
| | - Christian Rüegg
- Laboratory for Neutron Scattering and Imaging, Paul Scherrer Institute, 5232 Villigen, Switzerland.,Department of Quantum Matter Physics, University of Geneva, 1211 Genève, Switzerland
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74
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Magnetodielectric detection of magnetic quadrupole order in Ba(TiO)Cu 4(PO 4) 4 with Cu 4O 12 square cupolas. Nat Commun 2016; 7:13039. [PMID: 27698426 PMCID: PMC5059463 DOI: 10.1038/ncomms13039] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2016] [Accepted: 08/29/2016] [Indexed: 11/09/2022] Open
Abstract
In vortex-like spin arrangements, multiple spins can combine into emergent multipole moments. Such multipole moments have broken space-inversion and time-reversal symmetries, and can therefore exhibit linear magnetoelectric (ME) activity. Three types of such multipole moments are known: toroidal; monopole; and quadrupole moments. So far, however, the ME activity of these multipole moments has only been established experimentally for the toroidal moment. Here we propose a magnetic square cupola cluster, in which four corner-sharing square-coordinated metal-ligand fragments form a noncoplanar buckled structure, as a promising structural unit that carries an ME-active multipole moment. We substantiate this idea by observing clear magnetodielectric signals associated with an antiferroic ME-active magnetic quadrupole order in the real material Ba(TiO)Cu4(PO4)4. The present result serves as a useful guide for exploring and designing new ME-active materials based on vortex-like spin arrangements.
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75
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Donnerer C, Rahn MC, Sala MM, Vale JG, Pincini D, Strempfer J, Krisch M, Prabhakaran D, Boothroyd AT, McMorrow DF. All-in-all-Out Magnetic Order and Propagating Spin Waves in Sm_{2}Ir_{2}O_{7}. PHYSICAL REVIEW LETTERS 2016; 117:037201. [PMID: 27472131 DOI: 10.1103/physrevlett.117.037201] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/15/2016] [Indexed: 06/06/2023]
Abstract
Using resonant magnetic x-ray scattering we address the unresolved nature of the magnetic ground state and the low-energy effective Hamiltonian of Sm_{2}Ir_{2}O_{7}, a prototypical pyrochlore iridate with a finite temperature metal-insulator transition. Through a combination of elastic and inelastic measurements, we show that the magnetic ground state is an all-in-all-out (AIAO) antiferromagnet. The magnon dispersion indicates significant electronic correlations and can be well described by a minimal Hamiltonian that includes Heisenberg exchange [J=27.3(6) meV] and Dzyaloshinskii-Moriya interactions [D=4.9(3) meV], which provides a consistent description of the magnetic order and excitations. In establishing that Sm_{2}Ir_{2}O_{7} has the requisite inversion symmetry preserving AIAO magnetic ground state, our results support the notion that pyrochlore iridates may host correlated Weyl semimetals.
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Affiliation(s)
- C Donnerer
- London Centre for Nanotechnology and Department of Physics and Astronomy, University College London, London WC1E 6BT, United Kingdom
| | - M C Rahn
- Department of Physics, University of Oxford, Clarendon Laboratory, Oxford, OX1 3PU, United Kingdom
| | - M Moretti Sala
- ESRF-The European Synchrotron, CS 40220, 38043 Grenoble Cedex 9, France
| | - J G Vale
- London Centre for Nanotechnology and Department of Physics and Astronomy, University College London, London WC1E 6BT, United Kingdom
- Laboratory for Quantum Magnetism, Ecole Polytechnique Federale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
| | - D Pincini
- London Centre for Nanotechnology and Department of Physics and Astronomy, University College London, London WC1E 6BT, United Kingdom
- Diamond Light Source Ltd, Diamond House, Harwell Science and Innovation Campus, Didcot, Oxfordshire OX11 0DE, United Kingdom
| | - J Strempfer
- Deutsches Elektronen-Synchrotron DESY, Notkestrasse 85, D-22607 Hamburg, Germany
| | - M Krisch
- ESRF-The European Synchrotron, CS 40220, 38043 Grenoble Cedex 9, France
| | - D Prabhakaran
- Department of Physics, University of Oxford, Clarendon Laboratory, Oxford, OX1 3PU, United Kingdom
| | - A T Boothroyd
- Department of Physics, University of Oxford, Clarendon Laboratory, Oxford, OX1 3PU, United Kingdom
| | - D F McMorrow
- London Centre for Nanotechnology and Department of Physics and Astronomy, University College London, London WC1E 6BT, United Kingdom
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76
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Banerjee A, Bridges CA, Yan JQ, Aczel AA, Li L, Stone MB, Granroth GE, Lumsden MD, Yiu Y, Knolle J, Bhattacharjee S, Kovrizhin DL, Moessner R, Tennant DA, Mandrus DG, Nagler SE. Proximate Kitaev quantum spin liquid behaviour in a honeycomb magnet. NATURE MATERIALS 2016; 15:733-740. [PMID: 27043779 DOI: 10.1038/nmat4604] [Citation(s) in RCA: 210] [Impact Index Per Article: 26.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/11/2015] [Accepted: 02/22/2016] [Indexed: 06/05/2023]
Abstract
Quantum spin liquids (QSLs) are topological states of matter exhibiting remarkable properties such as the capacity to protect quantum information from decoherence. Whereas their featureless ground states have precluded their straightforward experimental identification, excited states are more revealing and particularly interesting owing to the emergence of fundamentally new excitations such as Majorana fermions. Ideal probes of these excitations are inelastic neutron scattering experiments. These we report here for a ruthenium-based material, α-RuCl3, continuing a major search (so far concentrated on iridium materials) for realizations of the celebrated Kitaev honeycomb topological QSL. Our measurements confirm the requisite strong spin-orbit coupling and low-temperature magnetic order matching predictions proximate to the QSL. We find stacking faults, inherent to the highly two-dimensional nature of the material, resolve an outstanding puzzle. Crucially, dynamical response measurements above interlayer energy scales are naturally accounted for in terms of deconfinement physics expected for QSLs. Comparing these with recent dynamical calculations involving gauge flux excitations and Majorana fermions of the pure Kitaev model, we propose the excitation spectrum of α-RuCl3 as a prime candidate for fractionalized Kitaev physics.
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Affiliation(s)
- A Banerjee
- Quantum Condensed Matter Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830, USA
| | - C A Bridges
- Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830, USA
| | - J-Q Yan
- Material Sciences and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830, USA
- Department of Materials Science and Engineering, University of Tennessee, Knoxville, Tennessee 37996, USA
| | - A A Aczel
- Quantum Condensed Matter Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830, USA
| | - L Li
- Department of Physics, University of Tennessee, Knoxville, Tennessee 37996, USA
| | - M B Stone
- Quantum Condensed Matter Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830, USA
| | - G E Granroth
- Quantum Condensed Matter Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830, USA
- Neutron Data Analysis &Visualization Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830, USA
| | - M D Lumsden
- Quantum Condensed Matter Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830, USA
| | - Y Yiu
- Department of Physics, University of Tennessee, Knoxville, Tennessee 37996, USA
| | - J Knolle
- Department of Physics, Cavendish Laboratory, J.J. Thomson Avenue, Cambridge CB3 0HE, UK
| | - S Bhattacharjee
- Max Planck Institute for the Physics of Complex Systems, D-01187 Dresden, Germany
- International Center for Theoretical Sciences, TIFR, Bangalore 560012, India
| | - D L Kovrizhin
- Department of Physics, Cavendish Laboratory, J.J. Thomson Avenue, Cambridge CB3 0HE, UK
| | - R Moessner
- Max Planck Institute for the Physics of Complex Systems, D-01187 Dresden, Germany
| | - D A Tennant
- Neutron Sciences Directorate, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830, USA
| | - D G Mandrus
- Material Sciences and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830, USA
- Department of Materials Science and Engineering, University of Tennessee, Knoxville, Tennessee 37996, USA
| | - S E Nagler
- Quantum Condensed Matter Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830, USA
- Bredesen Center, University of Tennessee, Knoxville, Tennessee 37966, USA
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77
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Mourigal M, Wu S, Stone MB, Neilson JR, Caron JM, McQueen TM, Broholm CL. Block Magnetic Excitations in the Orbitally Selective Mott Insulator BaFe_{2}Se_{3}. PHYSICAL REVIEW LETTERS 2015; 115:047401. [PMID: 26252707 DOI: 10.1103/physrevlett.115.047401] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/12/2014] [Indexed: 06/04/2023]
Abstract
Iron pnictides and selenides display a variety of unusual magnetic phases originating from the interplay between electronic, orbital, and lattice degrees of freedom. Using powder inelastic neutron scattering on the two-leg ladder BaFe_{2}Se_{3}, we fully characterize the static and dynamic spin correlations associated with the Fe_{4} block state, an exotic magnetic ground state observed in this low-dimensional magnet and in Rb_{0.89}Fe_{1.58}Se_{2}. All the magnetic excitations of the Fe_{4} block state predicted by an effective Heisenberg model with localized spins are observed below 300 meV and quantitatively reproduced. However, the data only account for 16(3)μ_{B}^{2} per Fe^{2+}, approximatively 2/3 of the total spectral weight expected for localized S=2 moments. Our results highlight how orbital degrees of freedom in iron-based magnets can conspire to stabilize an exotic magnetic state.
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Affiliation(s)
- M Mourigal
- Institute for Quantum Matter and Department of Physics and Astronomy, Johns Hopkins University, Baltimore, Maryland 21218, USA
| | - Shan Wu
- Institute for Quantum Matter and Department of Physics and Astronomy, Johns Hopkins University, Baltimore, Maryland 21218, USA
| | - M B Stone
- Quantum Condensed Matter Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - J R Neilson
- Institute for Quantum Matter and Department of Physics and Astronomy, Johns Hopkins University, Baltimore, Maryland 21218, USA
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, USA
| | - J M Caron
- Institute for Quantum Matter and Department of Physics and Astronomy, Johns Hopkins University, Baltimore, Maryland 21218, USA
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, USA
| | - T M McQueen
- Institute for Quantum Matter and Department of Physics and Astronomy, Johns Hopkins University, Baltimore, Maryland 21218, USA
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, USA
- Department of Materials Science and Engineering, Johns Hopkins University, Baltimore, Maryland 21218, USA
| | - C L Broholm
- Institute for Quantum Matter and Department of Physics and Astronomy, Johns Hopkins University, Baltimore, Maryland 21218, USA
- Quantum Condensed Matter Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
- Department of Materials Science and Engineering, Johns Hopkins University, Baltimore, Maryland 21218, USA
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78
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Ehlers G, Podlesnyak AA, Frontzek MD, Pushkarev AV, Shiryaev SV, Barilo S. Damped spin waves in the intermediate ordered phases in Ni3V2O8. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2015; 27:256003. [PMID: 26058062 DOI: 10.1088/0953-8984/27/25/256003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Spin dynamics in the intermediate ordered phases (between 4 and 9 K) in Ni3V2O8 have been studied with inelastic neutron scattering. It is found that the spin waves are very diffuse, indicative of short lived correlations and the coexistence of paramagnetic moments with the long-range ordered state.
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Affiliation(s)
- G Ehlers
- Quantum Condensed Matter Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831-6475, USA.
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