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Yasaka S, Yoshida Y, Tanaka Y, Nakamura Y, Kishida H, Kitagawa H, Maesato M. Electron Localization Induced by Disordered Anions in an Organic Conductor. Inorg Chem 2024; 63:4196-4203. [PMID: 38377386 DOI: 10.1021/acs.inorgchem.3c04226] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/22/2024]
Abstract
We report on a new organic conductor κ″-(ET)2Cu[N(CN)2]Br (κ″-Br), which is the first polymorph of an organic superconductor κ-(ET)2Cu[N(CN)2]Br (κ-Br), where ET denotes bis(ethylenedithio)tetrathiafulvalene. κ″-Br has a similar κ-type arrangement of ET molecules to κ-Br, but, in contrast to the orthorhombic κ-Br, which has ordered polyanion chains, presents a monoclinic crystal structure with disordered polymeric anion chains. To elucidate the electronic state of κ″-Br, we performed band calculations as well as transport, magnetic, and optical measurements. The calculated band dispersion, magnitude of electron correlation, and room-temperature optical conductivity spectra of κ″-Br were comparable to those of κ-Br. Despite these similarities, the κ″-Br salt exhibited a semiconducting behavior. The electron spin resonance and Raman spectroscopies indicated that there is neither magnetic nor charge order in κ″-Br, suggesting the occurrence of Anderson localization due to disordered anion layers.
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Affiliation(s)
- Soichiro Yasaka
- Division of Chemistry, Graduate School of Science, Kyoto University, Kitashirakawa-Oiwakecho, Sakyo-ku, Kyoto 606-8502, Japan
| | - Yukihiro Yoshida
- Division of Chemistry, Graduate School of Science, Kyoto University, Kitashirakawa-Oiwakecho, Sakyo-ku, Kyoto 606-8502, Japan
| | - Yuki Tanaka
- Division of Chemistry, Graduate School of Science, Kyoto University, Kitashirakawa-Oiwakecho, Sakyo-ku, Kyoto 606-8502, Japan
| | - Yuto Nakamura
- Department of Applied Physics, Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603, Japan
| | - Hideo Kishida
- Department of Applied Physics, Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603, Japan
| | - Hiroshi Kitagawa
- Division of Chemistry, Graduate School of Science, Kyoto University, Kitashirakawa-Oiwakecho, Sakyo-ku, Kyoto 606-8502, Japan
| | - Mitsuhiko Maesato
- Division of Chemistry, Graduate School of Science, Kyoto University, Kitashirakawa-Oiwakecho, Sakyo-ku, Kyoto 606-8502, Japan
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2
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Urai M, Miyagawa K, Watanabe Y, Zhilyaeva EI, Torunova SA, Lyubovskaya RN, Drichko N, Kanoda K. Anomalously field-susceptible spin clusters emerging in the electric-dipole liquid candidate κ-(ET) 2Hg(SCN) 2Br. SCIENCE ADVANCES 2022; 8:eabn1680. [PMID: 36542712 PMCID: PMC9771449 DOI: 10.1126/sciadv.abn1680] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/25/2021] [Accepted: 11/18/2022] [Indexed: 06/17/2023]
Abstract
Mutual interactions in many-body systems bring about various exotic phases, among which liquid-like states failing to order due to frustration are of keen interest. The organic system with an anisotropic triangular lattice of molecular dimers, κ-(ET)2Hg(SCN)2Br, has been suggested to host a dipole liquid arising from intradimer charge-imbalance instability, possibly offering an unprecedented stage for the spin degrees of freedom. Here, we show that an extraordinary unordered/unfrozen spin state having soft matter-like spatiotemporal characteristics emerges in this system. 1H nuclear magnetic resonance (NMR) spectra and magnetization measurements indicate that gigantic, staggered moments are nonlinearly and inhomogeneously induced by a magnetic field, whereas the moments vanish in the zero-field limit. The analysis of the NMR relaxation rate signifies that the moments fluctuate at a characteristic frequency slowing down to below megahertz at low temperatures. The inhomogeneity, local correlation, and slow dynamics indicative of middle-scale dynamical correlation length of several nanometers suggest novel frustration-driven spin clusterization.
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Affiliation(s)
- Mizuki Urai
- Department of Applied Physics, University of Tokyo, Tokyo 113-8656, Japan
| | - Kazuya Miyagawa
- Department of Applied Physics, University of Tokyo, Tokyo 113-8656, Japan
| | - Yuta Watanabe
- Department of Applied Physics, University of Tokyo, Tokyo 113-8656, Japan
| | - Elena I. Zhilyaeva
- Institute of Problems of Chemical Physics RAS, 142432 Chernogolovka, Russia
| | | | | | - Natalia Drichko
- The Institute for Quantum Matter and the Department of Physics and Astronomy, The Johns Hopkins University, Baltimore, MD 21218, USA
- The Institute for Solid State Physics, University of Tokyo, Kashiwa, Chiba 277-8581, Japan
| | - Kazushi Kanoda
- Department of Applied Physics, University of Tokyo, Tokyo 113-8656, Japan
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3
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Kobayashi A, Zhou B, Takagi R, Miyagawa K, Ishibashi S, Kobayashi A, Kawamura T, Nishibori E, Kanoda K. Single-Component Molecular Conductors — Multi-Orbital Correlated π-d Electron Systems. BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 2021. [DOI: 10.1246/bcsj.20210230] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- Akiko Kobayashi
- Department of Chemistry, College of Humanities and Sciences, Nihon University, Setagaya-ku, Tokyo 156-8550, Japan
| | - Biao Zhou
- Department of Chemistry, College of Humanities and Sciences, Nihon University, Setagaya-ku, Tokyo 156-8550, Japan
| | - Rina Takagi
- Department of Applied Physics, University of Tokyo, Bunkyo-ku, Tokyo 113-8656, Japan
- Institute of Engineering Innovation, University of Tokyo, Bunkyo-ku, Tokyo 113-0032, Japan
- PRESTO, Japan Science and Technology Agency (JST), Kawaguchi, Saitama 332-0012, Japan
| | - Kazuya Miyagawa
- Department of Applied Physics, University of Tokyo, Bunkyo-ku, Tokyo 113-8656, Japan
| | - Shoji Ishibashi
- Research Center for Computational Design of Advanced Functional Materials (CD-FMat), National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki 305-8568, Japan
| | - Akito Kobayashi
- Department of Physics, Nagoya University, Nagoya, Aichi 464-8602, Japan
| | - Taiki Kawamura
- Department of Physics, Nagoya University, Nagoya, Aichi 464-8602, Japan
| | - Eiji Nishibori
- Faculty of Pure and Applied Science and Tsukuba Research Center for Energy Materials Science (TREMS), University of Tsukuba, Tsukuba, Ibaraki 305-8571, Japan
| | - Kazushi Kanoda
- Department of Applied Physics, University of Tokyo, Bunkyo-ku, Tokyo 113-8656, Japan
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4
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Pressure-Tuned Superconducting Dome in Chemically-Substituted κ-(BEDT-TTF)2Cu2(CN)3. CRYSTALS 2021. [DOI: 10.3390/cryst11070817] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The quantum spin liquid candidate κ-(BEDT-TTF)2Cu2(CN)3 has been established as the prime example of a genuine Mott insulator that can be tuned across the first-order insulator–metal transition either by chemical substitution or by physical pressure. Here, we explore the superconducting state that occurs at low temperatures, when both methods are combined, i.e., when κ-[(BEDT-TTF)1−x(BEDT-STF)x]2Cu2(CN)3 is pressurized. We discovered superconductivity for partial BEDT-STF substitution with x = 0.10–0.12 even at ambient pressure, i.e., a superconducting state is realized in the range between a metal and a Mott insulator without magnetic order. Furthermore, we observed the formation of a superconducting dome by pressurizing the substituted crystals; we assigned this novel behavior to disorder emanating from chemical tuning.
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Miksch B, Pustogow A, Rahim MJ, Bardin AA, Kanoda K, Schlueter JA, Hübner R, Scheffler M, Dressel M. Gapped magnetic ground state in quantum spin liquid candidate κ-(BEDT-TTF) 2Cu 2(CN) 3. Science 2021; 372:276-279. [PMID: 33859031 DOI: 10.1126/science.abc6363] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2020] [Accepted: 03/09/2021] [Indexed: 02/02/2023]
Abstract
Geometrical frustration, quantum entanglement, and disorder may prevent long-range ordering of localized spins with strong exchange interactions, resulting in an exotic state of matter. κ-(BEDT-TTF)2Cu2(CN)3 is considered the prime candidate for this elusive quantum spin liquid state, but its ground-state properties remain puzzling. We present a multifrequency electron spin resonance (ESR) study down to millikelvin temperatures, revealing a rapid drop of the spin susceptibility at 6 kelvin. This opening of a spin gap, accompanied by structural modifications, is consistent with the formation of a valence bond solid ground state. We identify an impurity contribution to the ESR response that becomes dominant when the intrinsic spins form singlets. Probing the electrons directly manifests the pivotal role of defects for the low-energy properties of quantum spin systems without magnetic order.
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Affiliation(s)
- Björn Miksch
- Physikalisches Institut, Universität Stuttgart, 70569 Stuttgart, Germany
| | - Andrej Pustogow
- Physikalisches Institut, Universität Stuttgart, 70569 Stuttgart, Germany.,Department of Physics and Astronomy, University of California, Los Angeles, CA 90095, USA
| | | | - Andrey A Bardin
- Institute of Problems of Chemical Physics, Russian Academy of Sciences, Chernogolovka, Moscow Region 142432, Russia
| | - Kazushi Kanoda
- Department of Applied Physics, University of Tokyo, Tokyo 113-8656, Japan
| | - John A Schlueter
- Materials Science Division, Argonne National Laboratory, Argonne, IL 60439, USA.,National Science Foundation, Alexandria, VA 22314, USA
| | - Ralph Hübner
- Physikalisches Institut, Universität Stuttgart, 70569 Stuttgart, Germany
| | - Marc Scheffler
- Physikalisches Institut, Universität Stuttgart, 70569 Stuttgart, Germany
| | - Martin Dressel
- Physikalisches Institut, Universität Stuttgart, 70569 Stuttgart, Germany.
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Quantum spin-liquid states in an organic magnetic layer and molecular rotor hybrid. Proc Natl Acad Sci U S A 2020; 117:29555-29560. [PMID: 33154159 DOI: 10.1073/pnas.2000188117] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The exotic properties of quantum spin liquids (QSLs) have continually been of interest since Anderson's 1973 ground-breaking idea. Geometrical frustration, quantum fluctuations, and low dimensionality are the most often evoked material's characteristics that favor the long-range fluctuating spin state without freezing into an ordered magnet or a spin glass at low temperatures. Among the few known QSL candidates, organic crystals have the advantage of having rich chemistry capable of finely tuning their microscopic parameters. Here, we demonstrate the emergence of a QSL state in [EDT-TTF-CONH2]2 +[[Formula: see text]] (EDT-BCO), where the EDT molecules with spin-1/2 on a triangular lattice form layers which are separated by a sublattice of BCO molecular rotors. By several magnetic measurements, we show that the subtle random potential of frozen BCO Brownian rotors suppresses magnetic order down to the lowest temperatures. Our study identifies the relevance of disorder in the stabilization of QSLs.
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Kundu S, Hossain A, S PK, Das R, Baenitz M, Baker PJ, Orain JC, Joshi DC, Mathieu R, Mahadevan P, Pujari S, Bhattacharjee S, Mahajan AV, Sarma DD. Signatures of a Spin-1/2 Cooperative Paramagnet in the Diluted Triangular Lattice of Y_{2}CuTiO_{6}. PHYSICAL REVIEW LETTERS 2020; 125:117206. [PMID: 32975979 DOI: 10.1103/physrevlett.125.117206] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/19/2020] [Revised: 06/11/2020] [Accepted: 08/04/2020] [Indexed: 06/11/2023]
Abstract
We present a combination of thermodynamic and dynamic experimental signatures of a disorder driven dynamic cooperative paramagnet in a 50% site diluted triangular lattice spin-1/2 system: Y_{2}CuTiO_{6}. Magnetic ordering and spin freezing are absent down to 50 mK, far below the Curie-Weiss scale (-θ_{CW}) of ∼134 K. We observe scaling collapses of the magnetic field and temperature dependent magnetic heat capacity and magnetization data, respectively, in conformity with expectations from the random singlet physics. Our experiments establish the suppression of any freezing scale, if at all present, by more than 3 orders of magnitude, opening a plethora of interesting possibilities such as disorder stabilized long range quantum entangled ground states.
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Affiliation(s)
- S Kundu
- Department of Physics, Indian Institute of Technology, Bombay, Powai, Mumbai 400076, India
| | - Akmal Hossain
- Solid State and Structural Chemistry Unit, Indian Institute of Science, Bengaluru 560012, India
| | - Pranava Keerthi S
- Solid State and Structural Chemistry Unit, Indian Institute of Science, Bengaluru 560012, India
| | - Ranjan Das
- Solid State and Structural Chemistry Unit, Indian Institute of Science, Bengaluru 560012, India
| | - M Baenitz
- Max Planck Institute for Chemical Physics of Solids, 01187 Dresden, Germany
| | - Peter J Baker
- ISIS Pulsed Neutron and Muon Source, STFC Rutherford Appleton Laboratory, Harwell Campus, Didcot, Oxfordshire OX110QX, United Kingdom
| | | | - D C Joshi
- Department of Engineering Sciences, Uppsala University, Box 534, SE-751 21 Uppsala, Sweden
| | - Roland Mathieu
- Department of Engineering Sciences, Uppsala University, Box 534, SE-751 21 Uppsala, Sweden
| | - Priya Mahadevan
- S. N. Bose National Center for Basic Sciences, Block-JD, Salt Lake, Kolkata-700106, India
| | - Sumiran Pujari
- Department of Physics, Indian Institute of Technology, Bombay, Powai, Mumbai 400076, India
| | - Subhro Bhattacharjee
- International Centre for Theoretical Sciences, Tata Institute of Fundamental Research, Bengaluru 560089, India
| | - A V Mahajan
- Department of Physics, Indian Institute of Technology, Bombay, Powai, Mumbai 400076, India
| | - D D Sarma
- Solid State and Structural Chemistry Unit, Indian Institute of Science, Bengaluru 560012, India
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8
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Tomeno S, Maesato M, Yoshida Y, Kiswandhi A, Kitagawa H. Triangular-Lattice Organic Mott Insulator with a Disorder-Free Polyanion. Inorg Chem 2020; 59:8647-8651. [PMID: 32538624 DOI: 10.1021/acs.inorgchem.0c00880] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We report the synthesis, crystal and band structures, and transport properties of organic conductor κ-(ET)2Cu[Au(CN)2]Cl [ET = bis(ethylenedithio)tetrathiafulvalene], which has a triangular spin-lattice (S = 1/2) composed of (ET)2•+ dimers and polyanions with no disorder. The anisotropy of triangular lattice t'/t = 1.19 and physical properties indicate that this material is the first ET-based quantum-spin-liquid candidate having a nearly regular triangular lattice with a disorder-free anion.
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Affiliation(s)
- Shinya Tomeno
- Division of Chemistry, Graduate School of Science, Kyoto University, Kitashirakawa-Oiwakecho, Sakyo-ku, Kyoto 606-8502, Japan
| | - Mitsuhiko Maesato
- Division of Chemistry, Graduate School of Science, Kyoto University, Kitashirakawa-Oiwakecho, Sakyo-ku, Kyoto 606-8502, Japan
| | - Yukihiro Yoshida
- Division of Chemistry, Graduate School of Science, Kyoto University, Kitashirakawa-Oiwakecho, Sakyo-ku, Kyoto 606-8502, Japan
| | - Andhika Kiswandhi
- Division of Chemistry, Graduate School of Science, Kyoto University, Kitashirakawa-Oiwakecho, Sakyo-ku, Kyoto 606-8502, Japan.,Institute for Solid State Physics, The University of Tokyo, Kashiwanoha, Kashiwa, Chiba 277-8581, Japan
| | - Hiroshi Kitagawa
- Division of Chemistry, Graduate School of Science, Kyoto University, Kitashirakawa-Oiwakecho, Sakyo-ku, Kyoto 606-8502, Japan
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9
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Urai M, Miyagawa K, Sasaki T, Taniguchi H, Kanoda K. Quantum Disordering of an Antiferromagnetic Order by Quenched Randomness in an Organic Mott Insulator. PHYSICAL REVIEW LETTERS 2020; 124:117204. [PMID: 32242676 DOI: 10.1103/physrevlett.124.117204] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/04/2019] [Accepted: 02/18/2020] [Indexed: 06/11/2023]
Abstract
The behavior of interacting spins subject to randomness is a longstanding issue and the emergence of exotic quantum states is among intriguing theoretical predictions. We show how a quantum-disordered phase emerges from a classical antiferromagnet by controlled randomness. ^{1}H NMR of a successively x-ray-irradiated organic Mott insulator finds that the magnetic order collapses into a spin-glass-like state, immediately after a slight amount of disorder centers are created, and evolves to a gapless quantum-disordered state without spin freezing, spin gap, or critical slowing down, as reported by T. Furukawa et al. [Phys. Rev. Lett. 115, 077001 (2015)]PRLTAO0031-900710.1103/PhysRevLett.115.077001 through sequential reductions in the spin freezing temperature and moment.
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Affiliation(s)
- Mizuki Urai
- Department of Applied Physics, University of Tokyo, Tokyo 113-8656, Japan
| | - Kazuya Miyagawa
- Department of Applied Physics, University of Tokyo, Tokyo 113-8656, Japan
| | - Takahiko Sasaki
- Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
| | - Hiromi Taniguchi
- Department of Physics, Saitama University, Saitama 338-8570, Japan
| | - Kazushi Kanoda
- Department of Applied Physics, University of Tokyo, Tokyo 113-8656, Japan
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10
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Yamamoto R, Furukawa T, Miyagawa K, Sasaki T, Kanoda K, Itou T. Electronic Griffiths Phase in Disordered Mott-Transition Systems. PHYSICAL REVIEW LETTERS 2020; 124:046404. [PMID: 32058734 DOI: 10.1103/physrevlett.124.046404] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/02/2019] [Indexed: 06/10/2023]
Abstract
Solid-state physics and soft-matter physics have been developed independently, with little mutual exchange of the underlying physical concepts. However, after many studies of correlated electron systems, it has been recognized that correlated electrons (especially in Mott-transition systems) in solid matter sometimes show behavior similar to "structured fluids" in soft matter; that is, the electrons exhibit long-length self-organization (but without long-range order) and slow dynamics, which is inevitable for the long-length structures. The essential question is this: what condition causes such behavior in solid matter? We focused on an organic Mott-transition system and demonstrated that the electrons of this system fluctuate very slowly only when the following two factors are met simultaneously: (i) the electronic system is on the metal and Mott-insulator boundary and (ii) the system is subject to quenched disorder. This electronic state with slow dynamics under this condition can be explained by the concept of the "(electronic) Griffiths phase." This concept will potentially be a key in connecting solid-state physics with soft-matter physics.
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Affiliation(s)
- Riku Yamamoto
- Department of Applied Physics, Tokyo University of Science, Tokyo 125-8585, Japan
| | - Tetsuya Furukawa
- Department of Applied Physics, Tokyo University of Science, Tokyo 125-8585, Japan
| | - Kazuya Miyagawa
- Department of Applied Physics, University of Tokyo, Tokyo 113-8656, Japan
| | - Takahiko Sasaki
- Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
| | - Kazushi Kanoda
- Department of Applied Physics, University of Tokyo, Tokyo 113-8656, Japan
| | - Tetsuaki Itou
- Department of Applied Physics, Tokyo University of Science, Tokyo 125-8585, Japan
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11
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Kawamura H, Uematsu K. Nature of the randomness-induced quantum spin liquids in two dimensions. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2019; 31:504003. [PMID: 31470422 DOI: 10.1088/1361-648x/ab400c] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
The nature of the randomness-induced quantum spin liquid state, the random-singlet state, is investigated in two dimensions (2D) by means of the exact-diagonalization and the Hams-de Raedt methods for several frustrated lattices, e.g. the triangular, the kagome and the J 1-J 2 square lattices. Properties of the ground state, the low-energy excitations and the finite-temperature thermodynamic quantities are investigated. The ground state and the low-lying excited states consist of nearly isolated singlet-dimers, clusters of resonating singlet-dimers, and orphan spins. Low-energy excitations are either singlet-to-triplet excitations, diffusion of orphan spins accompanied by the recombination of nearby singlet-dimers, creation or destruction of resonating singlet-dimers clusters. The latter two excitations give enhanced dynamical 'liquid-like' features to the 2D random-singlet state. Comparison is made with the random-singlet state in a 1D chain without frustration, the similarity and the difference between in 1D and in 2D being highlighted. Frustration in a wide sense, not only the geometrical one but also including the one arising from the competition between distinct types of interactions, play an essential role in stabilizing this frustrated random singlet state. Recent experimental situations on both organic and inorganic materials are reviewed and discussed.
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Affiliation(s)
- Hikaru Kawamura
- Department of Earth and Space Science, Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043, Japan
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12
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Riedl K, Valentí R, Winter SM. Critical spin liquid versus valence-bond glass in a triangular-lattice organic antiferromagnet. Nat Commun 2019; 10:2561. [PMID: 31189897 PMCID: PMC6561973 DOI: 10.1038/s41467-019-10604-3] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2018] [Accepted: 05/15/2019] [Indexed: 11/23/2022] Open
Abstract
In the quest for materials with unconventional quantum phases, the organic triangular-lattice antiferromagnet κ-(ET)2Cu2(CN)3 has been extensively discussed as a quantum spin liquid (QSL) candidate. The description of its low temperature properties has become, however, a particularly challenging task. Recently, an intriguing quantum critical behaviour was suggested from low-temperature magnetic torque experiments. Here we highlight significant deviations of the experimental observations from a quantum critical scenario by performing a microscopic analysis of all anisotropic contributions, including Dzyaloshinskii-Moriya and multi-spin scalar chiral interactions. Instead, we show that disorder-induced spin defects provide a comprehensive explanation of the low-temperature properties. These spins are attributed to valence bond defects that emerge spontaneously as the QSL enters a valence-bond glass phase at low temperature. This theoretical treatment is applicable to a general class of frustrated magnetic systems and has important implications for the interpretation of magnetic torque, nuclear magnetic resonance, thermal transport and thermodynamic experiments.
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Affiliation(s)
- Kira Riedl
- Institut für Theoretische Physik, Goethe-Universität Frankfurt, Max-von-Laue-Strasse 1, 60438, Frankfurt am Main, Germany.
| | - Roser Valentí
- Institut für Theoretische Physik, Goethe-Universität Frankfurt, Max-von-Laue-Strasse 1, 60438, Frankfurt am Main, Germany
| | - Stephen M Winter
- Institut für Theoretische Physik, Goethe-Universität Frankfurt, Max-von-Laue-Strasse 1, 60438, Frankfurt am Main, Germany.
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Bhowal S, Ganguly S, Dasgupta I. Spin-orbit coupling driven novel magnetism in d 5 6H-perovskite iridates Ba 3IrTi 2O 9 and Ba 3TiIr 2O 9. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2019; 31:185802. [PMID: 30721889 DOI: 10.1088/1361-648x/ab048c] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
In the present paper, we have carried out a comparative first principles as well as model Hamiltonian study to understand the novel magnetism in 6H perovskite iridates Ba3IrTi2O9 and Ba3TiIr2O9 resulting from an unusual combination of geometrical as well as exchange frustration owing to their unique crystal geometry. Our model calculations corroborated with multipolar analysis provides a comprehensive understanding of the spin-orbit entangled [Formula: see text] pseudo-spin states in both materials. While, the [Formula: see text] character is quite robust in the former compound, it is found to be directly related to the nature of magnetism in the latter iridate. The identification of the relevant spin model for the ideal structure of Ba3IrTi2O9 suggests that the Heisenberg exchange interaction dominates the Kitaev term favoring long range magnetic order in the system in line with the ab initio study while the other iridate Ba3TiIr2O9 has the posibility to host novel spin-orbital singlet state with no resultant moment.
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Affiliation(s)
- Sayantika Bhowal
- School of Physical Sciences, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700 032, India
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14
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Pustogow A, Saito Y, Zhukova E, Gorshunov B, Kato R, Lee TH, Fratini S, Dobrosavljević V, Dressel M. Low-Energy Excitations in Quantum Spin Liquids Identified by Optical Spectroscopy. PHYSICAL REVIEW LETTERS 2018; 121:056402. [PMID: 30118313 DOI: 10.1103/physrevlett.121.056402] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/03/2018] [Indexed: 06/08/2023]
Abstract
The electrodynamic response of organic spin liquids with highly frustrated triangular lattices has been measured in a wide energy range. While the overall optical spectra of these Mott insulators are governed by transitions between the Hubbard bands, distinct in-gap excitations can be identified at low temperatures and frequencies, which we attribute to the quantum-spin-liquid state. For the strongly correlated β^{'}-EtMe_{3}Sb[Pd(dmit)_{2}]_{2}, we discover enhanced conductivity below 175 cm^{-1}, comparable to the energy of the magnetic coupling J≈250 K. For ω→0, these low-frequency excitations vanish faster than the charge-carrier response subject to Mott-Hubbard correlations, resulting in a dome-shaped band peaked at 100 cm^{-1}. Possible relations to spinons, magnons, and disorder are discussed.
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Affiliation(s)
- A Pustogow
- 1. Physikalisches Institut, Universität Stuttgart, Pfaffenwaldring 57, D-70550 Stuttgart, Germany
| | - Y Saito
- 1. Physikalisches Institut, Universität Stuttgart, Pfaffenwaldring 57, D-70550 Stuttgart, Germany
- Department of Physics, Hokkaido University, Sapporo 060-0810, Japan
| | - E Zhukova
- Moscow Institute of Physics and Technology (State University), 141700, Dolgoprudny, Moscow Region, Russia
| | - B Gorshunov
- Moscow Institute of Physics and Technology (State University), 141700, Dolgoprudny, Moscow Region, Russia
| | - R Kato
- Condensed Molecular Materials Laboratory, RIKEN, Wako-shi, Saitama 351-0198, Japan
| | - T-H Lee
- Department of Physics and National High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida 32306, USA
| | - S Fratini
- Institut Néel-CNRS and Université Grenoble Alpes, 38042 Grenoble Cedex 9, France
| | - V Dobrosavljević
- Department of Physics and National High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida 32306, USA
| | - M Dressel
- 1. Physikalisches Institut, Universität Stuttgart, Pfaffenwaldring 57, D-70550 Stuttgart, Germany
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16
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Mustonen O, Vasala S, Sadrollahi E, Schmidt KP, Baines C, Walker HC, Terasaki I, Litterst FJ, Baggio-Saitovitch E, Karppinen M. Spin-liquid-like state in a spin-1/2 square-lattice antiferromagnet perovskite induced by d 10-d 0 cation mixing. Nat Commun 2018. [PMID: 29540711 PMCID: PMC5852160 DOI: 10.1038/s41467-018-03435-1] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
A quantum spin liquid state has long been predicted to arise in spin-1/2 Heisenberg square-lattice antiferromagnets at the boundary region between Néel (nearest-neighbor interaction dominates) and columnar (next-nearest-neighbor interaction dominates) antiferromagnetic order. However, there are no known compounds in this region. Here we use d10-d0 cation mixing to tune the magnetic interactions on the square lattice while simultaneously introducing disorder. We find spin-liquid-like behavior in the double perovskite Sr2Cu(Te0.5W0.5)O6, where the isostructural end phases Sr2CuTeO6 and Sr2CuWO6 are Néel and columnar type antiferromagnets, respectively. We show that magnetism in Sr2Cu(Te0.5W0.5)O6 is entirely dynamic down to 19 mK. Additionally, we observe at low temperatures for Sr2Cu(Te0.5W0.5)O6-similar to several spin liquid candidates-a plateau in muon spin relaxation rate and a strong T-linear dependence in specific heat. Our observations for Sr2Cu(Te0.5W0.5)O6 highlight the role of disorder in addition to magnetic frustration in spin liquid physics.
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Affiliation(s)
- O Mustonen
- Department of Chemistry and Materials Science, Aalto University, FI-00076, Espoo, Finland
| | - S Vasala
- Centro Brasileiro de Pesquisas Físicas (CBPF), Rua Dr Xavier Sigaud 150, Urca, Rio de Janeiro, 22290-180, Brazil
| | - E Sadrollahi
- Institut für Physik der Kondensierten Materie, Technische Universität Braunschweig, 38110, Braunschweig, Germany
| | - K P Schmidt
- Institut für Physik der Kondensierten Materie, Technische Universität Braunschweig, 38110, Braunschweig, Germany
| | - C Baines
- Laboratory for Muon Spin Spectroscopy, Paul Scherrer Institut, 5232, Villigen PSI, Switzerland
| | - H C Walker
- ISIS Neutron and Muon Source, Rutherford Appleton Laboratory, Chilton, Didcot, OX11 0QX, UK
| | - I Terasaki
- Department of Physics, Nagoya University, Nagoya, 464-8602, Japan
| | - F J Litterst
- Centro Brasileiro de Pesquisas Físicas (CBPF), Rua Dr Xavier Sigaud 150, Urca, Rio de Janeiro, 22290-180, Brazil.,Institut für Physik der Kondensierten Materie, Technische Universität Braunschweig, 38110, Braunschweig, Germany
| | - E Baggio-Saitovitch
- Centro Brasileiro de Pesquisas Físicas (CBPF), Rua Dr Xavier Sigaud 150, Urca, Rio de Janeiro, 22290-180, Brazil
| | - M Karppinen
- Department of Chemistry and Materials Science, Aalto University, FI-00076, Espoo, Finland.
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17
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Effects of Disorder on the Pressure-Induced Mott Transition in κ-(BEDT-TTF)2Cu[N(CN)2]Cl. CRYSTALS 2018. [DOI: 10.3390/cryst8010038] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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18
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Savary L, Balents L. Quantum spin liquids: a review. REPORTS ON PROGRESS IN PHYSICS. PHYSICAL SOCIETY (GREAT BRITAIN) 2017; 80:016502. [PMID: 27823986 DOI: 10.1088/0034-4885/80/1/016502] [Citation(s) in RCA: 296] [Impact Index Per Article: 42.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Quantum spin liquids may be considered 'quantum disordered' ground states of spin systems, in which zero-point fluctuations are so strong that they prevent conventional magnetic long-range order. More interestingly, quantum spin liquids are prototypical examples of ground states with massive many-body entanglement, which is of a degree sufficient to render these states distinct phases of matter. Their highly entangled nature imbues quantum spin liquids with unique physical aspects, such as non-local excitations, topological properties, and more. In this review, we discuss the nature of such phases and their properties based on paradigmatic models and general arguments, and introduce theoretical technology such as gauge theory and partons, which are conveniently used in the study of quantum spin liquids. An overview is given of the different types of quantum spin liquids and the models and theories used to describe them. We also provide a guide to the current status of experiments in relation to study quantum spin liquids, and to the diverse probes used therein.
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Affiliation(s)
- Lucile Savary
- Department of Physics, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
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19
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Norman MR. Materials design for new superconductors. REPORTS ON PROGRESS IN PHYSICS. PHYSICAL SOCIETY (GREAT BRITAIN) 2016; 79:074502. [PMID: 27214291 DOI: 10.1088/0034-4885/79/7/074502] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Since the announcement in 2011 of the Materials Genome Initiative by the Obama administration, much attention has been given to the subject of materials design to accelerate the discovery of new materials that could have technological implications. Although having its biggest impact for more applied materials like batteries, there is increasing interest in applying these ideas to predict new superconductors. This is obviously a challenge, given that superconductivity is a many body phenomenon, with whole classes of known superconductors lacking a quantitative theory. Given this caveat, various efforts to formulate materials design principles for superconductors are reviewed here, with a focus on surveying the periodic table in an attempt to identify cuprate analogues.
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Affiliation(s)
- M R Norman
- Materials Science Division, Argonne National Laboratory, Argonne, IL 60439, USA
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20
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Lenz B, Manmana SR, Pruschke T, Assaad FF, Raczkowski M. Mott Quantum Criticality in the Anisotropic 2D Hubbard Model. PHYSICAL REVIEW LETTERS 2016; 116:086403. [PMID: 26967431 DOI: 10.1103/physrevlett.116.086403] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/03/2015] [Indexed: 06/05/2023]
Abstract
We present evidence for Mott quantum criticality in an anisotropic two-dimensional system of coupled Hubbard chains at half-filling. In this scenario emerging from variational cluster approximation and cluster dynamical mean-field theory, the interchain hopping t_{⊥} acts as a control parameter driving the second-order critical end point T_{c} of the metal-insulator transition down to zero at t_{⊥}^{c}/t≃0.2. Below t_{⊥}^{c}, the volume of the hole and electron Fermi pockets of a compensated metal vanishes continuously at the Mott transition. Above t_{⊥}^{c}, the volume reduction of the pockets is cut off by a first-order transition. We discuss the relevance of our findings to a putative quantum critical point in layered organic conductors, whose location remains elusive so far.
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Affiliation(s)
- Benjamin Lenz
- Institute for Theoretical Physics, University of Göttingen, Friedrich-Hund-Platz 1, D-37077 Göttingen, Germany
| | - Salvatore R Manmana
- Institute for Theoretical Physics, University of Göttingen, Friedrich-Hund-Platz 1, D-37077 Göttingen, Germany
| | - Thomas Pruschke
- Institute for Theoretical Physics, University of Göttingen, Friedrich-Hund-Platz 1, D-37077 Göttingen, Germany
| | - Fakher F Assaad
- Institute for Theoretical Physics and Astrophysics, University of Würzburg, Am Hubland, D-97074 Würzburg, Germany
| | - Marcin Raczkowski
- Institute for Theoretical Physics and Astrophysics, University of Würzburg, Am Hubland, D-97074 Würzburg, Germany
- Department of Physics and Arnold Sommerfeld Center for Theoretical Physics, Ludwig-Maximilians-Universität München, D-80333 München, Germany
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