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Abstract
Recently, Co-based honeycomb magnets have been proposed as promising candidate materials to host the Kitaev spin liquid (KSL) state. One of the front-runners is BaCo2(AsO4)2 (BCAO), where it was suggested that the exchange processes between Co2+ ions via the surrounding edge-sharing oxygen octahedra could give rise to bond-dependent Kitaev interactions. In this work, we present and analyze a comprehensive inelastic neutron scattering (INS) study of BCAO with fields in the honeycomb plane. Combining the constraints from the magnon excitations in the high-field polarized state and the inelastic spin structure factor measured in zero magnetic field, we examine two leading theoretical models: the Kitaev-type [Formula: see text] model and the XXZ[Formula: see text]model. We show that the existing experimental data can be consistently accounted for by the XXZ[Formula: see text]model but not by the [Formula: see text] model, and we discuss the implications of these results for the realization of a spin liquid phase in BCAO and more generally for the realization of the Kitaev model in cobaltates.
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Zhang X, Xu Y, Halloran T, Zhong R, Broholm C, Cava RJ, Drichko N, Armitage NP. A magnetic continuum in the cobalt-based honeycomb magnet BaCo 2(AsO 4) 2. NATURE MATERIALS 2023; 22:58-63. [PMID: 36411349 DOI: 10.1038/s41563-022-01403-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/11/2021] [Accepted: 10/10/2022] [Indexed: 06/16/2023]
Abstract
Quantum spin liquids (QSLs) are topologically ordered states of matter that host fractionalized excitations. A particular route towards a QSL is via strongly bond-dependent interactions on the hexagonal lattice. A number of Ru- and Ir-based candidate Kitaev QSL materials have been pursued, but all have appreciable non-Kitaev interactions. Using time-domain terahertz spectroscopy, we observed a broad magnetic continuum over a wide range of temperatures and fields in the honeycomb cobalt-based magnet BaCo2(AsO4)2, which has been proposed to be a more ideal version of a Kitaev QSL. Applying an in-plane magnetic field of ~0.5 T suppresses the magnetic order, and at higher fields, applying the field gives rise to a spin-polarized state. Under a 4 T magnetic field that was oriented principally out of plane, a broad magnetic continuum was observed that may be consistent with a field-induced QSL. Our results indicate BaCo2(AsO4)2 is a promising QSL candidate.
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Affiliation(s)
- Xinshu Zhang
- Institute for Quantum Matter, Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD, USA
| | - Yuanyuan Xu
- Institute for Quantum Matter, Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD, USA
| | - T Halloran
- Institute for Quantum Matter, Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD, USA
| | - Ruidan Zhong
- Department of Chemistry, Princeton University, Princeton, NJ, USA
| | - C Broholm
- Institute for Quantum Matter, Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD, USA
- NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, MD, USA
- Department of Materials Science and Engineering, Johns Hopkins University, Baltimore, MD, USA
| | - R J Cava
- Department of Chemistry, Princeton University, Princeton, NJ, USA
| | - N Drichko
- Institute for Quantum Matter, Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD, USA
| | - N P Armitage
- Institute for Quantum Matter, Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD, USA.
- Canadian Institute for Advanced Research, Toronto, Ontario, Canada.
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A Mero-Plesiotype Series of Vanadates, Arsenates, and Phosphates with Blocks Based on Densely Packed Octahedral Layers as Repeating Modules. MINERALS 2021. [DOI: 10.3390/min11030273] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The family of layered vanadates, arsenates, and phosphates is discussed in terms of a modular concept. The group includes minerals vésignéite and bayldonite, and a number of synthetic analogous and modifications which are not isotypic, but their crystal structures comprise similar blocks (modules) consisting of a central octahedral layer filled by atoms of d elements (Mn, Ni, Cu, or Co) and adjacent [VO4], [AsO4], or [PO4] tetrahedra. The octahedral layers are based on the close-packing of oxygen atoms. Within these layers having the same anionic substructure, the number and distribution of octahedral voids are different. In the crystal structures of compounds participating in the polysomatic series, these blocks alternate with various other structural fragments. These circumstances define the row of structurally-related vanadates, arsenates, and phosphates as a mero-plesiotype series. Most of the series members exhibit magnetic properties, representing two-dimensional antiferromagnets or frustrated magnets.
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Van Hove singularity in the magnon spectrum of the antiferromagnetic quantum honeycomb lattice. Nat Commun 2021; 12:171. [PMID: 33420023 PMCID: PMC7794317 DOI: 10.1038/s41467-020-20335-5] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2020] [Accepted: 11/24/2020] [Indexed: 11/08/2022] Open
Abstract
In quantum magnets, magnetic moments fluctuate heavily and are strongly entangled with each other, a fundamental distinction from classical magnetism. Here, with inelastic neutron scattering measurements, we probe the spin correlations of the honeycomb lattice quantum magnet YbCl3. A linear spin wave theory with a single Heisenberg interaction on the honeycomb lattice, including both transverse and longitudinal channels of the neutron response, reproduces all of the key features in the spectrum. In particular, we identify a Van Hove singularity, a clearly observable sharp feature within a continuum response. The demonstration of such a Van Hove singularity in a two-magnon continuum is important as a confirmation of broadly held notions of continua in quantum magnetism and additionally because analogous features in two-spinon continua could be used to distinguish quantum spin liquids from merely disordered systems. These results establish YbCl3 as a benchmark material for quantum magnetism on the honeycomb lattice.
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Motome Y, Sano R, Jang S, Sugita Y, Kato Y. Materials design of Kitaev spin liquids beyond the Jackeli-Khaliullin mechanism. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2020; 32:404001. [PMID: 32235048 DOI: 10.1088/1361-648x/ab8525] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/17/2020] [Accepted: 03/31/2020] [Indexed: 06/11/2023]
Abstract
The Kitaev spin liquid provides a rare example of well-established quantum spin liquids in more than one dimension. It is obtained as the exact ground state of the Kitaev spin model with bond-dependent anisotropic interactions. The peculiar interactions can be yielded by the synergy of spin-orbit coupling and electron correlations for specific electron configuration and lattice geometry, which is known as the Jackeli-Khaliullin mechanism. Based on this mechanism, there has been a fierce race for the materialization of the Kitaev spin liquid over the last decade, but the candidates have been still limited mostly to 4d- and 5d-electron compounds including cations with the low-spind5electron configuration, such as Ir4+and Ru3+. Here we discuss recent efforts to extend the material perspective beyond the Jackeli-Khaliullin mechanism, by carefully reexamining the two requisites, formation of thejeff= 1/2 doublet and quantum interference between the exchange processes, for not onlyd- but alsof-electron systems. We present three examples: the systems including Co2+and Ni3+with the high-spind7electron configuration, Pr4+with thef1-electron configuration, and polar asymmetry in the lattice structure. In particular, the latter two are intriguing since they may realize the antiferromagnetic Kitaev interactions, in contrast to the ferromagnetic ones in the existing candidates. This partial overview would stimulate further material exploration of the Kitaev spin liquids and its topological properties due to fractional excitations.
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Affiliation(s)
- Yukitoshi Motome
- Department of Applied Physics, University of Tokyo, Bunkyo, Tokyo 113-8656, Japan
| | - Ryoya Sano
- Department of Applied Physics, University of Tokyo, Bunkyo, Tokyo 113-8656, Japan
| | - Seonghoon Jang
- Department of Applied Physics, University of Tokyo, Bunkyo, Tokyo 113-8656, Japan
| | - Yusuke Sugita
- Department of Applied Physics, University of Tokyo, Bunkyo, Tokyo 113-8656, Japan
| | - Yasuyuki Kato
- Department of Applied Physics, University of Tokyo, Bunkyo, Tokyo 113-8656, Japan
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Zhong R, Gao T, Ong NP, Cava RJ. Weak-field induced nonmagnetic state in a Co-based honeycomb. SCIENCE ADVANCES 2020; 6:eaay6953. [PMID: 32042902 PMCID: PMC6981077 DOI: 10.1126/sciadv.aay6953] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/10/2019] [Accepted: 11/21/2019] [Indexed: 06/10/2023]
Abstract
Layered honeycomb magnets are of interest as potential realizations of the Kitaev quantum spin liquid (KQSL), a quantum state with long-range spin entanglement and an exactly solvable Hamiltonian. Conventional magnetically ordered states are present for all currently known candidate materials, however, because non-Kitaev terms in the Hamiltonians obscure the Kitaev physics. Current experimental studies of the KQSL are focused on 4d or 5d transition metal-based honeycombs, in which strong spin-orbit coupling can be expected, yielding Kitaev interaction that dominates in an applied magnetic field. In contrast, for 3d-based layered honeycomb magnets, spin-orbit coupling is weak, and thus, Kitaev physics should be substantially less accessible. Here, we report our studies on BaCo2(AsO4)2, for which we find that the magnetic order associated with the non-Kitaev interactions can be fully suppressed by a relatively low magnetic field, yielding a nonmagnetic material and implying the presence of strong magnetic frustration and weak non-Kitaev interactions.
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Affiliation(s)
- Ruidan Zhong
- Department of Chemistry, Princeton University, Princeton, NJ 08544, USA
| | - Tong Gao
- Department of Physics, Princeton University, Princeton, NJ 08544, USA
| | - Nai Phuan Ong
- Department of Physics, Princeton University, Princeton, NJ 08544, USA
| | - Robert J. Cava
- Department of Chemistry, Princeton University, Princeton, NJ 08544, USA
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