1
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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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2
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Huang Y, Mitchell T, Zheng Y, Hu Y, Benedict JB, Seo JH, Ren S. Switching charge states in quasi-2D molecular conductors. PNAS NEXUS 2022; 1:pgac089. [PMID: 36741426 PMCID: PMC9896912 DOI: 10.1093/pnasnexus/pgac089] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/26/2022] [Accepted: 06/08/2022] [Indexed: 06/18/2023]
Abstract
2D molecular entities build next-generation electronic devices, where abundant elements of organic molecules are attractive due to the modern synthetic and stimuli control through chemical, conformational, and electronic modifications in electronics. Despite its promising potential, the insufficient control over charge states and electronic stabilities must be overcome in molecular electronic devices. Here, we show the reversible switching of modulated charge states in an exfoliatable 2D-layered molecular conductor based on bis(ethylenedithio)tetrathiafulvalene molecular dimers. The multiple stimuli application of cooling rate, current, voltage, and laser irradiation in a concurrent manner facilitates the controllable manipulation of charge crystal, glass, liquid, and metal phases. The four orders of magnitude switching of electric resistance are triggered by stimuli-responsive charge distribution among molecular dimers. The tunable charge transport in 2D molecular conductors reveals the kinetic process of charge configurations under stimuli, promising to add electric functions in molecular circuitry.
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Affiliation(s)
- Yulong Huang
- Department of Mechanical and Aerospace Engineering, University at Buffalo, The State University of New York, Buffalo, NY 14260, USA
| | - Travis Mitchell
- Department of Chemistry, University at Buffalo, The State University of New York, Buffalo, NY 14260, USA
| | - Yixiong Zheng
- Department of Materials Design and Innovation, University at Buffalo, The State University of New York, Buffalo, NY 14260, USA
| | - Yong Hu
- Department of Mechanical and Aerospace Engineering, University at Buffalo, The State University of New York, Buffalo, NY 14260, USA
| | - Jason B Benedict
- Department of Chemistry, University at Buffalo, The State University of New York, Buffalo, NY 14260, USA
| | - Jung-Hun Seo
- Department of Materials Design and Innovation, University at Buffalo, The State University of New York, Buffalo, NY 14260, USA
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3
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Berlie A, Terry I, Szablewski M, Telling M, Apperley D, Hodgkinson P, Zeller D. A study of the dynamics and structure of the dielectric anomaly within the molecular solid TEA(TCNQ) 2. Phys Chem Chem Phys 2022; 24:7481-7492. [PMID: 35274651 DOI: 10.1039/d2cp00142j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
With rising interest in organic-based functional materials, it is important to understand the nature of magnetic and electrical transitions within these types of systems. One intriguing material is triethylammonium bis-7,7,8,8-tetracyanoquinodimethane (TEA(TCNQ)2) where there is an order-disorder transition at ∼220 K. This work focuses on novel neutron scattering techniques to understand the motion of the TEA cations at this transition and explain why we see the dielectric behaviour and possible ferroelectricity within this type of system. We show that the motion of the methyl groups of the TEA cation is spatially restricted below 220 K, whereas above the dielectric anomaly at 220 K, they are free to re-orientate, which ultimately leads to some rich behaviour that could be further exploited. Lastly, we also study the dynamics at this transition using a variety of additional techniques, helping to provide a consistent picture of the motions of the cations.
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Affiliation(s)
- Adam Berlie
- ISIS Neutron and Muon Source, STFC Rutherford Appleton Laboratory, Chilton, Oxfordshire, OX11 0QX, UK.
| | - Ian Terry
- Department of Physics, Durham University, South Road, Durham, DH1 3LE, UK
| | - Marek Szablewski
- Department of Physics, Durham University, South Road, Durham, DH1 3LE, UK
| | - Mark Telling
- ISIS Neutron and Muon Source, STFC Rutherford Appleton Laboratory, Chilton, Oxfordshire, OX11 0QX, UK.
| | - David Apperley
- Department of Chemistry, Durham University, South Road, Durham, DH1 3LE, UK
| | - Paul Hodgkinson
- Department of Chemistry, Durham University, South Road, Durham, DH1 3LE, UK
| | - Dominik Zeller
- Institut Laue Langevin, BP 156, 38042 Grenoble Cedex 9, France
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4
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Huang Y, Mitchell T, Yost DC, Hu Y, Benedict JB, Grossman JC, Ren S. Emerged Metallicity in Molecular Ferromagnetic Wires. NANO LETTERS 2021; 21:9746-9753. [PMID: 34757755 DOI: 10.1021/acs.nanolett.1c03663] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Supramolecular engineering bridges molecular assembly with macromolecular charge-transfer salts, promising the design to construct supramolecular architectures that integrate cooperative properties difficult or impossible to find in conventional lattices. Here, we report the crystal engineering design and kinetic growth of one-dimensional supramolecular wires composed of bis(ethylenedithio)tetrathiafulvalene (ET+) cation and polymeric Cu[N(CN)2]2- anion. A bulk ferromagnetic order is discovered for filling up the gap where strong ferromagnetism is missing in such ET molecule-based charge-transfer salts. Metallicity is induced by electric current from the semiconducting wire, which is attributed to strain effect by tuning its close molecular contact. This structural feature is evidenced through the combination of various mechanistic spectroscopic studies. Electric dipole is established from the close molecular contacts and is suggestive to stabilize ferromagnetic spin interaction through anions bridging spin sites. The breakthrough shown here provides a pathway to explore low-dimensional supramolecular materials exhibiting strong electron correlation, metallicity, and ferromagnetism.
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Affiliation(s)
- Yulong Huang
- Department of Mechanical and Aerospace Engineering, University at Buffalo, The State University of New York, Buffalo, New York 14260, United States
| | - Travis Mitchell
- Department of Chemistry, University at Buffalo, The State University of New York, Buffalo, New York 14260, United States
| | - Dillon C Yost
- Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Yong Hu
- Department of Mechanical and Aerospace Engineering, University at Buffalo, The State University of New York, Buffalo, New York 14260, United States
| | - Jason B Benedict
- Department of Chemistry, University at Buffalo, The State University of New York, Buffalo, New York 14260, United States
| | - Jeffrey C Grossman
- Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Shenqiang Ren
- Department of Mechanical and Aerospace Engineering, University at Buffalo, The State University of New York, Buffalo, New York 14260, United States
- Department of Chemistry, University at Buffalo, The State University of New York, Buffalo, New York 14260, United States
- Research and Education in energy, Environment and Water (RENEW) Institute, University at Buffalo, The State University of New York, Buffalo, New York 14260, United States
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5
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Yamakawa H, Miyamoto T, Morimoto T, Takamura N, Liang S, Yoshimochi H, Terashige T, Kida N, Suda M, Yamamoto HM, Mori H, Miyagawa K, Kanoda K, Okamoto H. Terahertz-field-induced polar charge order in electronic-type dielectrics. Nat Commun 2021; 12:953. [PMID: 33574221 PMCID: PMC7878852 DOI: 10.1038/s41467-021-20925-x] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2020] [Accepted: 12/29/2020] [Indexed: 11/09/2022] Open
Abstract
Ultrafast electronic-phase change in solids by light, called photoinduced phase transition, is a central issue in the field of non-equilibrium quantum physics, which has been developed very recently. In most of those phenomena, charge or spin orders in an original phase are melted by photocarrier generations, while an ordered state is usually difficult to be created from a non-ordered state by a photoexcitation. Here, we demonstrate that a strong terahertz electric-field pulse changes a Mott insulator of an organic molecular compound in κ-(ET)2Cu[N(CN)2]Cl (ET = bis(ethylenedithio)tetrathiafulvalene), to a macroscopically polarized charge-order state; herein, electronic ferroelectricity is induced by the collective intermolecular charge transfers in each dimer. In contrast, in an isostructural compound, κ-(ET)2Cu2(CN)3, which shows the spin-liquid state at low temperatures, a similar polar charge order is not stabilized by the same terahertz pulse. From the comparative studies of terahertz-field-induced second-harmonic-generation and reflectivity changes in the two compounds, we suggest the possibility that a coupling of charge and spin degrees of freedom would play important roles in the stabilization of polar charge order.
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Affiliation(s)
- H Yamakawa
- Department of Advanced Materials Science, University of Tokyo, Chiba, 277-8561, Japan
| | - T Miyamoto
- Department of Advanced Materials Science, University of Tokyo, Chiba, 277-8561, Japan.
| | - T Morimoto
- Department of Advanced Materials Science, University of Tokyo, Chiba, 277-8561, Japan
| | - N Takamura
- Department of Advanced Materials Science, University of Tokyo, Chiba, 277-8561, Japan
| | - S Liang
- Department of Advanced Materials Science, University of Tokyo, Chiba, 277-8561, Japan
| | - H Yoshimochi
- Department of Applied Physics, University of Tokyo, Bunkyo-Ku, 113-8656, Japan
| | - T Terashige
- AIST-UTokyo Advanced Operand-Measurement Technology Open Innovation Laboratory, National Institute of Advanced Industrial Science and Technology, Chiba, 277-8589, Japan
| | - N Kida
- Department of Advanced Materials Science, University of Tokyo, Chiba, 277-8561, Japan
| | - M Suda
- Division of Functional Molecular Systems, Research Center of Integrative Molecular Systems (CIMoS), Institute for Molecular Science, Okazaki, 444-8585, Japan.,Department of Molecular Engineering, Kyoto University, Kyoto, 615-8510, Japan
| | - H M Yamamoto
- Division of Functional Molecular Systems, Research Center of Integrative Molecular Systems (CIMoS), Institute for Molecular Science, Okazaki, 444-8585, Japan
| | - H Mori
- Institute for Solid State Physics, University of Tokyo, Chiba, 277-8581, Japan
| | - K Miyagawa
- Department of Applied Physics, University of Tokyo, Bunkyo-Ku, 113-8656, Japan
| | - K Kanoda
- Department of Applied Physics, University of Tokyo, Bunkyo-Ku, 113-8656, Japan
| | - H Okamoto
- Department of Advanced Materials Science, University of Tokyo, Chiba, 277-8561, Japan. .,AIST-UTokyo Advanced Operand-Measurement Technology Open Innovation Laboratory, National Institute of Advanced Industrial Science and Technology, Chiba, 277-8589, Japan.
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6
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Electric dipole induced bulk ferromagnetism in dimer Mott molecular compounds. Sci Rep 2021; 11:1332. [PMID: 33446711 PMCID: PMC7809364 DOI: 10.1038/s41598-020-79262-6] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2020] [Accepted: 12/07/2020] [Indexed: 11/17/2022] Open
Abstract
Magnetic properties of Mott–Hubbard systems are generally dominated by strong antiferromagnetic interactions produced by the Coulomb repulsion of electrons. Although theoretical possibility of a ferromagnetic ground state has been suggested by Nagaoka and Penn as single-hole doping in a Mott insulator, experimental realization has not been reported more than half century. We report the first experimental possibility of such ferromagnetism in a molecular Mott insulator with an extremely light and homogeneous hole-doping in π-electron layers induced by net polarization of counterions. A series of Ni(dmit)2 anion radical salts with organic cations, where dmit is 1,3-dithiole-2-thione-4,5-dithiolate can form bi-layer structure with polarized cation layers. Heat capacity, magnetization, and ESR measurements substantiated the formation of a bulk ferromagnetic state around 1.0 K with quite soft magnetization versus magnetic field (M–H) characteristics in (Et-4BrT)[Ni(dmit)2]2 where Et-4BrT is ethyl-4-bromothiazolium. The variation of the magnitude of net polarizations by using the difference of counter cations revealed the systematic change of the ground state from antiferromagnetic one to ferromagnetic one. We also report emergence of metallic states through further doping and applying external pressures for this doping induced ferromagnetic state. The realization of ferromagnetic state in Nagaoka–Penn mechanism can paves a way for designing new molecules-based ferromagnets in future.
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7
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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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8
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Otsuka A, Shimizu Y, Saito G, Maesato M, Kiswandhi A, Hiramatsu T, Yoshida Y, Yamochi H, Tsuchiizu M, Nakamura Y, Kishida H, Ito H. Canting Antiferromagnetic Spin-Order ( TN = 102 K) in a Monomer Mott Insulator (ET)Ag 4(CN) 5 with a Diamond Spin-Lattice. BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 2020. [DOI: 10.1246/bcsj.20190279] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- Akihiro Otsuka
- Department of Chemistry, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan
- Research Center for Low Temperature and Materials Sciences, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan
| | - Yasuhiro Shimizu
- Department of Physics, Graduate School of Science, Nagoya University, Nagoya, Aichi 464-8602, Japan
| | - Gunzi Saito
- Faculty of Agriculture, Meijo University, 1-501 Shiogamaguchi, Tempaku-ku, Nagoya, Aichi 468-8502, Japan
- Toyota Physical and Chemical Research Institute, Nagakute, Aichi 480-1192, Japan
| | - Mitsuhiko Maesato
- Department of Chemistry, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan
| | - Andhika Kiswandhi
- Department of Chemistry, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan
| | - Takaaki Hiramatsu
- Faculty of Agriculture, Meijo University, 1-501 Shiogamaguchi, Tempaku-ku, Nagoya, Aichi 468-8502, Japan
| | - Yukihiro Yoshida
- Department of Chemistry, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan
- Faculty of Agriculture, Meijo University, 1-501 Shiogamaguchi, Tempaku-ku, Nagoya, Aichi 468-8502, Japan
| | - Hideki Yamochi
- Department of Chemistry, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan
- Research Center for Low Temperature and Materials Sciences, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan
| | | | - Yuto Nakamura
- Department of Applied Physics, Nagoya University, Chikusa-ku, Nagoya, Aichi 464-8603, Japan
| | - Hideo Kishida
- Department of Applied Physics, Nagoya University, Chikusa-ku, Nagoya, Aichi 464-8603, Japan
| | - Hiroshi Ito
- Department of Applied Physics, Nagoya University, Chikusa-ku, Nagoya, Aichi 464-8603, Japan
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9
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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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10
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Abstract
Abstract
Multiferroic materials, showing ordering of both electrical and magnetic degrees of freedom, are promising candidates enabling the design of novel electronic devices. Various mechanisms ranging from geometrically or spin-driven improper ferroelectricity via lone-pairs, charge-order or -transfer support multiferroicity in single-phase or composite compounds. The search for materials showing these effects constitutes one of the most important research fields in solid-state physics during the last years, but scientific interest even traces back to the middle of the past century. Especially, a potentially strong coupling between spin and electric dipoles captured the interest to control via an electric field the magnetization or via a magnetic field the electric polarization. This would imply a promising route for novel electronics. Here, we provide a review about the dielectric and ferroelectric properties of various multiferroic systems ranging from type I multiferroics, in which magnetic and ferroelectric order develop almost independently of each other, to type II multiferroics, which exhibit strong coupling of magnetic and ferroelectric ordering. We thoroughly discuss the dielectric signatures of the ferroelectric polarization for BiFeO3, Fe3O4, DyMnO3 and an organic charge-transfer salt as well as show electric-field poling studies for the hexagonal manganites and a spin-spiral system LiCuVO4.
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11
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Matsuura M, Sasaki T, Iguchi S, Gati E, Müller J, Stockert O, Piovano A, Böhm M, Park JT, Biswas S, Winter SM, Valentí R, Nakao A, Lang M. Lattice Dynamics Coupled to Charge and Spin Degrees of Freedom in the Molecular Dimer-Mott Insulator κ-(BEDT-TTF)_{2}Cu[N(CN)_{2}]Cl. PHYSICAL REVIEW LETTERS 2019; 123:027601. [PMID: 31386497 DOI: 10.1103/physrevlett.123.027601] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/28/2018] [Revised: 05/24/2019] [Indexed: 06/10/2023]
Abstract
Inelastic neutron scattering measurements on the molecular dimer-Mott insulator κ-(BEDT-TTF)_{2}Cu[N(CN)_{2}]Cl reveal a phonon anomaly in a wide temperature range. Starting from T_{ins}∼50-60 K where the charge gap opens, the low-lying optical phonon modes become overdamped upon cooling towards the antiferromagnetic ordering temperature T_{N}=27 K, where also a ferroelectric ordering at T_{FE}≈T_{N} occurs. Conversely, the phonon damping becomes small again when spins and charges are ordered below T_{N}, while no change of the lattice symmetry is observed across T_{N} in neutron diffraction measurements. We assign the phonon anomalies to structural fluctuations coupled to charge and spin degrees of freedom in the BEDT-TTF molecules.
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Affiliation(s)
- Masato Matsuura
- Neutron Science and Technology Center, Comprehensive Research Organization for Science and Society (CROSS), Tokai, Ibaraki 319-1106, Japan
| | - Takahiko Sasaki
- Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
| | - Satoshi Iguchi
- Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
| | - Elena Gati
- Institute of Physics, Goethe-University Frankfurt, 60438 Frankfurt (M), Germany
| | - Jens Müller
- Institute of Physics, Goethe-University Frankfurt, 60438 Frankfurt (M), Germany
| | - Oliver Stockert
- Max-Planck-Institut für Chemische Physik fester Stoffe, D-01187 Dresden, Germany
| | - Andrea Piovano
- Institut Laue-Langevin, 71 avenue des Martyrs, 38042 Grenoble Cedex 9, France
| | - Martin Böhm
- Institut Laue-Langevin, 71 avenue des Martyrs, 38042 Grenoble Cedex 9, France
| | - Jitae T Park
- Heinz Maier-Leibnitz Zentrum (MLZ), Technische Universität München, Lichtenbergstr. 1, 85748 Garching, Germany
| | - Sananda Biswas
- Institute for Theoretical Physics, Goethe-University Frankfurt, 60438 Frankfurt (M), Germany
| | - Stephen M Winter
- Institute for Theoretical Physics, Goethe-University Frankfurt, 60438 Frankfurt (M), Germany
| | - Roser Valentí
- Institute for Theoretical Physics, Goethe-University Frankfurt, 60438 Frankfurt (M), Germany
| | - Akiko Nakao
- Neutron Science and Technology Center, Comprehensive Research Organization for Science and Society (CROSS), Tokai, Ibaraki 319-1106, Japan
| | - Michael Lang
- Institute of Physics, Goethe-University Frankfurt, 60438 Frankfurt (M), Germany
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12
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Gati E, Fischer JKH, Lunkenheimer P, Zielke D, Köhler S, Kolb F, von Nidda HAK, Winter SM, Schubert H, Schlueter JA, Jeschke HO, Valentí R, Lang M. Evidence for Electronically Driven Ferroelectricity in a Strongly Correlated Dimerized BEDT-TTF Molecular Conductor. PHYSICAL REVIEW LETTERS 2018; 120:247601. [PMID: 29957011 DOI: 10.1103/physrevlett.120.247601] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/20/2017] [Indexed: 06/08/2023]
Abstract
By applying measurements of the dielectric constants and relative length changes to the dimerized molecular conductor κ-(BEDT-TTF)_{2}Hg(SCN)_{2}Cl, we provide evidence for order-disorder type electronic ferroelectricity that is driven by the charge order within the (BEDT-TTF)_{2} dimers and stabilized by a coupling to the anions. According to our density functional theory calculations, this material is characterized by a moderate strength of dimerization. This system thus bridges the gap between strongly dimerized materials, often approximated as dimer-Mott systems at 1/2 filling, and nondimerized or weakly dimerized systems at 1/4 filling, exhibiting a charge order. Our results indicate that intradimer charge degrees of freedom are of particular importance in correlated κ-(BEDT-TTF)_{2}X salts and can create novel states, such as electronically driven multiferroicity or charge-order-induced quasi-one-dimensional spin liquids.
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Affiliation(s)
- Elena Gati
- Institute of Physics, Goethe-Universität, Max-von-Laue-Straße 1, 60438 Frankfurt am Main, Germany
| | - Jonas K H Fischer
- Experimental Physics V, Center for Electronic Correlations and Magnetism, University of Augsburg, 86159 Augsburg, Germany
| | - Peter Lunkenheimer
- Experimental Physics V, Center for Electronic Correlations and Magnetism, University of Augsburg, 86159 Augsburg, Germany
| | - David Zielke
- Institute of Physics, Goethe-Universität, Max-von-Laue-Straße 1, 60438 Frankfurt am Main, Germany
| | - Sebastian Köhler
- Institute of Physics, Goethe-Universität, Max-von-Laue-Straße 1, 60438 Frankfurt am Main, Germany
| | - Felizitas Kolb
- Experimental Physics V, Center for Electronic Correlations and Magnetism, University of Augsburg, 86159 Augsburg, Germany
| | - Hans-Albrecht Krug von Nidda
- Experimental Physics V, Center for Electronic Correlations and Magnetism, University of Augsburg, 86159 Augsburg, Germany
| | - Stephen M Winter
- Institute for Theoretical Physics, Goethe-Universität, Max-von-Laue-Straße 1, 60438 Frankfurt am Main, Germany
| | - Harald Schubert
- Institute of Physics, Goethe-Universität, Max-von-Laue-Straße 1, 60438 Frankfurt am Main, Germany
| | - John A Schlueter
- Division of Materials Research, National Science Foundation, Arlington, Virginia 22230, USA
- Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439, USA
| | - Harald O Jeschke
- Institute for Theoretical Physics, Goethe-Universität, Max-von-Laue-Straße 1, 60438 Frankfurt am Main, Germany
- Research Institute for Interdisciplinary Science, Okayama University, 3-1-1 Tsushima-naka, Kita-ku, Okayama 700-8530, Japan
| | - Roser Valentí
- Institute for Theoretical Physics, Goethe-Universität, Max-von-Laue-Straße 1, 60438 Frankfurt am Main, Germany
| | - Michael Lang
- Institute of Physics, Goethe-Universität, Max-von-Laue-Straße 1, 60438 Frankfurt am Main, Germany
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Low-Frequency Dynamics of Strongly Correlated Electrons in (BEDT-TTF)2X Studied by Fluctuation Spectroscopy. CRYSTALS 2018. [DOI: 10.3390/cryst8040166] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Fluctuation spectroscopy measurements of quasi-two-dimensional organic charge-transfer salts (BEDT-TTF) 2 X are reviewed. In the past decade, the method has served as a new approach for studying the low-frequency dynamics of strongly correlated charge carriers in these materials. We review some basic aspects of electronic fluctuations in solids, and give an overview of selected problems where the analysis of 1 / f -type fluctuations and the corresponding slow dynamics provide a better understanding of the underlying physics. These examples are related to (1) an inhomogeneous current distribution due to phase separation and/or a percolative transition; (2) slow dynamics due to a glassy freezing either of structural degrees of freedom coupling to the electronic properties or (3) of the electrons themselves, e.g., when residing on a highly-frustrated crystal lattice, where slow and heterogeneous dynamics are key experimental properties for the vitrification process of a supercooled charge-liquid. Another example is (4), the near divergence and critical slowing down of charge carrier fluctuations at the finite-temperature critical endpoint of the Mott metal-insulator transition. Here also indications for a glassy freezing and temporal and spatial correlated dynamics are found. Mapping out the region of ergodicity breaking and understanding the influence of disorder on the temporal and spatial correlated fluctuations will be an important realm of future studies, as well as the fluctuation properties deep in the Mott or charge-ordered insulating states providing a connection to relaxor or ordered ferroelectric states studied by dielectric spectroscopy.
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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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17
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Hiramatsu T, Yoshida Y, Saito G, Otsuka A, Yamochi H, Maesato M, Shimizu Y, Ito H, Nakamura Y, Kishida H, Watanabe M, Kumai R. Design and Preparation of a Quantum Spin Liquid Candidateκ-(ET)2Ag2(CN)3Having a Nearby Superconductivity. BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 2017. [DOI: 10.1246/bcsj.20170167] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- Takaaki Hiramatsu
- Faculty of Agriculture, Meijo University, 1-501 Shiogamaguchi, Tempaku-ku, Nagoya 468-8502
| | - Yukihiro Yoshida
- Faculty of Agriculture, Meijo University, 1-501 Shiogamaguchi, Tempaku-ku, Nagoya 468-8502
- Division of Chemistry, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto 606-8502
| | - Gunzi Saito
- Faculty of Agriculture, Meijo University, 1-501 Shiogamaguchi, Tempaku-ku, Nagoya 468-8502
- Toyota Physical and Chemical Research Institute, Nagakute 480-1192
| | - Akihiro Otsuka
- Division of Chemistry, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto 606-8502
- Research Center for Low Temperature and Materials Sciences, Kyoto University, Sakyo-ku, Kyoto 606-8501
| | - Hideki Yamochi
- Division of Chemistry, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto 606-8502
- Research Center for Low Temperature and Materials Sciences, Kyoto University, Sakyo-ku, Kyoto 606-8501
| | - Mitsuhiko Maesato
- Division of Chemistry, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto 606-8502
| | - Yasuhiro Shimizu
- Department of Physics, Graduate School of Science, Nagoya University, Chikusa-ku, Nagoya 464-8602
| | - Hiroshi Ito
- Department of Applied Physics, Nagoya University, Chikusa-ku, Nagoya 464-8603
| | - Yuto Nakamura
- Department of Applied Physics, Nagoya University, Chikusa-ku, Nagoya 464-8603
| | - Hideo Kishida
- Department of Applied Physics, Nagoya University, Chikusa-ku, Nagoya 464-8603
| | - Masashi Watanabe
- Frontier Research Initiative, New Industry Creation Hatchery Center, Tohoku University, Aoba-ku, Sendai 980-8579
| | - Reiji Kumai
- Condensed Matter Research Center (CMRC) and Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), Tsukuba 305-0801
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Lunkenheimer P, Loidl A. Dielectric spectroscopy on organic charge-transfer salts. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2015; 27:373001. [PMID: 26325011 DOI: 10.1088/0953-8984/27/37/373001] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
This topical review provides an overview of the dielectric properties of a variety of organic charge-transfer salts, based on both, data reported in literature and our own experimental results. Moreover, we discuss in detail the different processes that can contribute to the dielectric response of these materials. We concentrate on the family of the 1D (TMTTF)2 X systems and the 2D BEDT-TTF-based charge-transfer salts, which in recent years have attracted considerable interest due to their often intriguing dielectric properties. We will mainly focus on the occurrence of electronic ferroelectricity in these systems, which also includes examples of multiferroicity.
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Affiliation(s)
- P Lunkenheimer
- Experimental Physics V, Center for Electronic Correlations and Magnetism, University of Augsburg, 86159 Augsburg, Germany
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Furukawa T, Miyagawa K, Itou T, Ito M, Taniguchi H, Saito M, Iguchi S, Sasaki T, Kanoda K. Quantum Spin Liquid Emerging from Antiferromagnetic Order by Introducing Disorder. PHYSICAL REVIEW LETTERS 2015; 115:077001. [PMID: 26317741 DOI: 10.1103/physrevlett.115.077001] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/19/2015] [Indexed: 06/04/2023]
Abstract
Quantum spin liquids, which are spin versions of quantum matter, have been sought after in systems with geometrical frustration. We show that disorder drives a classical magnet into a quantum spin liquid through conducting NMR experiments on an organic Mott insulator, κ-(ET)_{2}Cu[N(CN)_{2}]Cl. Antiferromagnetic ordering in the pristine crystal, when irradiated by x rays, disappears. Spin freezing, spin gap, and critical slowing down are not observed, but gapless spin excitations emerge, suggesting a novel role of disorder that brings forth a quantum spin liquid from a classical ordered state.
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Affiliation(s)
- T Furukawa
- Department of Applied Physics, University of Tokyo, Tokyo 113-8656, Japan
| | - K Miyagawa
- Department of Applied Physics, University of Tokyo, Tokyo 113-8656, Japan
| | - T Itou
- Department of Applied Physics, Tokyo University of Science, Tokyo 125-8585, Japan
| | - M Ito
- Department of Physics, Saitama University, Saitama 338-8570, Japan
| | - H Taniguchi
- Department of Physics, Saitama University, Saitama 338-8570, Japan
| | - M Saito
- Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
| | - S Iguchi
- Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
| | - T Sasaki
- Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
| | - K Kanoda
- Department of Applied Physics, University of Tokyo, Tokyo 113-8656, Japan
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20
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de Souza M, Bartosch L. Probing the Mott physics in κ-(BEDT-TTF)₂X salts via thermal expansion. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2015; 27:053203. [PMID: 25603958 DOI: 10.1088/0953-8984/27/5/053203] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
In the field of interacting electron systems the Mott metal-to-insulator (MI) transition represents one of the pivotal issues. The role played by lattice degrees of freedom for the Mott MI transition and the Mott criticality in a variety of materials are current topics under debate. In this context, molecular conductors of the κ-(BEDT-TTF)2X type constitute a class of materials for unraveling several aspects of the Mott physics. In this review, we present a synopsis of literature results with focus on recent expansivity measurements probing the Mott MI transition in this class of materials. Progress in the description of the Mott critical behavior is also addressed.
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Affiliation(s)
- Mariano de Souza
- Departamento de Física, Instituto de Geociências e Ciências Exatas-IGCE, Unesp-Universidade Estadual Paulista, Cx. Postal 178, 13506-900 Rio Claro (SP), Brazil. Physikalisches Institut, Goethe-Universität, Max-von-Laue-Str. 1, 60438 Frankfurt am Main, Germany
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Konarev DV, Khasanov SS, Otsuka A, Maesato M, Uruichi M, Yakushi K, Shevchun AF, Yamochi H, Saito G, Lyubovskaya RN. Metallic and Mott insulating spin-frustrated antiferromagnetic states in ionic fullerene complexes with a two-dimensional hexagonal C60·- packing motif. Chemistry 2014; 20:7268-77. [PMID: 24838699 DOI: 10.1002/chem.201304763] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2013] [Revised: 03/29/2014] [Indexed: 11/05/2022]
Abstract
(MDABCO(+))(C60(·-))(TPC) (1), in which MDABCO(+) is N-methyldiazabicyclooctanium, TPC is triptycene, and both have threefold symmetry, is a rare example of a fullerene-based quasi-2D metal and contains closely packed hexagonal fullerene layers with interfullerene center-to-center distances of 10.07 Å at 300 K. Evidence for the metallic nature of 1 was obtained by optical and microwave conductivity measurements on single crystals. The metal is characterized by a nontypical Drude response and relatively large optical mass (m*/m0 =6.7). The latter indicates a narrow-band nature, which is consistent with the calculated bandwidth of 0.10-0.15 eV. The coexistence of metallic and antiferromagnetic nonmetallic 2D layers was observed in 1 above 200-230 K. It was assumed that the nonmetallic layers undergo a transition to the metallic state below 200 K due to ordering of the fullerene and cationic sublattices. New layered complex (MQ(+))(C60(·-))(TPC) (2) with a hexagonal arrangement of C60(·-) was obtained by increasing the interfullerene distance with the bulkier N-methylquinuclidinium cations (MQ(+)) having threefold symmetry. The structure of 2 is characterized by increased interfullerene center-to-center distances in the layers (10.124, 10.155, and 10.177 Å at 250 K). Unit-cell doubling parallel to the 2D layer (along the b axis) was observed at low temperatures. In contrast to metallic 1, 2 exhibits a nonmetallic spin-frustrated state with an antiferromagnetic interaction of spins (the Weiss temperature is -27 K) and no magnetic ordering down to 1.9 K. It was supposed that the expanded interfullerene distances in the triangular arrangement decrease the bandwidth and suppress metallic conductivity in 2, and thus a Mott-Hubbard insulating state with antiferromagnetically frustrated spins results.
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Affiliation(s)
- Dmitri V Konarev
- Institute of Problems of Chemical Physics RAS, Chernogolovka, Moscow region, 142432 (Russia).
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Lunkenheimer P, Müller J, Krohns S, Schrettle F, Loidl A, Hartmann B, Rommel R, de Souza M, Hotta C, Schlueter JA, Lang M. Multiferroicity in an organic charge-transfer salt that is suggestive of electric-dipole-driven magnetism. NATURE MATERIALS 2012; 11:755-758. [PMID: 22886065 DOI: 10.1038/nmat3400] [Citation(s) in RCA: 77] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/08/2011] [Accepted: 07/13/2012] [Indexed: 06/01/2023]
Abstract
Multiferroics, showing simultaneous ordering of electrical and magnetic degrees of freedom, are remarkable materials as seen from both the academic and technological points of view. A prominent mechanism of multiferroicity is the spin-driven ferroelectricity, often found in frustrated antiferromagnets with helical spin order. There, as for conventional ferroelectrics, the electrical dipoles arise from an off-centre displacement of ions. However, recently a different mechanism, namely purely electronic ferroelectricity, where charge order breaks inversion symmetry, has attracted considerable interest. Here we provide evidence for ferroelectricity, accompanied by antiferromagnetic spin order, in a two-dimensional organic charge-transfer salt, thus representing a new class of multiferroics. We propose a charge-order-driven mechanism leading to electronic ferroelectricity in this material. Quite unexpectedly for electronic ferroelectrics, dipolar and spin order arise nearly simultaneously. This can be ascribed to the loss of spin frustration induced by the ferroelectric ordering. Hence, here the spin order is driven by the ferroelectricity, in marked contrast to the spin-driven ferroelectricity in helical magnets.
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23
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Spin and Charge Transport in the X-ray Irradiated Quasi-2D Layered Compound: κ-(BEDT-TTF)2Cu[N(CN)2]Cl. CRYSTALS 2012. [DOI: 10.3390/cryst2020579] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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25
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Müller J. Fluctuation Spectroscopy: A New Approach for Studying Low‐Dimensional Molecular Metals. Chemphyschem 2011; 12:1222-45. [DOI: 10.1002/cphc.201000814] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2010] [Indexed: 11/12/2022]
Affiliation(s)
- Jens Müller
- Institute of Physics, Goethe University Frankfurt, Max‐von‐Laue‐Str. 1, 60438 Frankfurt (M) (Germany), Fax: (+49) 69‐798‐47227
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Abstract
We review the development of conductive organic molecular assemblies including organic metals, superconductors, single component conductors, conductive films, conductors with a switching function, and new spin state (quantum spin liquid state). We emphasize the importance of the ionicity phase diagram for a variety of charge transfer systems to provide a strategy for the development of functional organic solids (Mott insulator, semiconductor, superconductor, metal, complex isomer, neutral-ionic system, alignment of chemical potentials, etc.). For organic (super)conductors, the electronic dimensionality of the solids is a key parameter and can be designed based on the self-aggregation ability of a molecule. We present characteristic structural and physical properties of organic superconductors.
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Mercuri ML, Deplano P, Pilia L, Serpe A, Artizzu F. Interactions modes and physical properties in transition metal chalcogenolene-based molecular materials. Coord Chem Rev 2010. [DOI: 10.1016/j.ccr.2009.10.002] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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Itaya M, Eto Y, Kawamoto A, Taniguchi H. Antiferromagnetic fluctuations in the organic superconductor kappa-(BEDT-TTF)2Cu(NCS)_{2} under pressure. PHYSICAL REVIEW LETTERS 2009; 102:227003. [PMID: 19658892 DOI: 10.1103/physrevlett.102.227003] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/09/2009] [Indexed: 05/28/2023]
Abstract
We measured the 13C-NMR spectrum and T1 of the quasi-two-dimensional organic superconductor kappa-(BEDT-TTF)2Cu(NCS)_{2} under pressure. This material was thought to show a relationship between T_{c} and the effective cyclotron mass m_{c};{*}, obtained from the Shubnikov-de Haas (SdH) effect. We found that kappa-(BEDT-TTF)2Cu(NCS)_{2} behaved as a Fermi liquid at low temperature under all pressures, and antiferromagnetic fluctuations were expected. The pressure dependence of the Korringa factor is similar to that of the effective cyclotron mass m_{c};{*}, suggesting that antiferromagnetic fluctuations contribute to the superconductivity of this material. We also found that, under pressure, T;{*} was shifted to 150 K, the temperature characteristic of the shift from bad metal to good metal.
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Affiliation(s)
- Megumi Itaya
- Department of Quantum and Condensed Matter Physics, Graduate School of Science, Hokkaido University, Kita-ku, Sapporo, Hokkaido 060-0810, Japan
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Sasaki T, Yoneyama N. Spatial mapping of electronic states in κ-(BEDT-TTF) 2X using infrared reflectivity. SCIENCE AND TECHNOLOGY OF ADVANCED MATERIALS 2009; 10:024306. [PMID: 27877279 PMCID: PMC5090436 DOI: 10.1088/1468-6996/10/2/024306] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/09/2008] [Revised: 07/06/2009] [Accepted: 01/19/2009] [Indexed: 06/03/2023]
Abstract
We review our recent work on spatial inhomogeneity of the electronic states in the strongly correlated molecular conductors κ-(BEDT-TTF)2X. Spatial mapping of infrared spectra (SMIS) is used for imaging the distribution of the local electronic states. In molecular materials, the infrared response of the specific molecular vibration mode with a strong electron-molecular vibration coupling can reflect the electronic states via the change in the vibration frequency. By spatially mapping the frequency shift of the molecular vibration mode, an electronic phase separation has been visualized near the first-order Mott transition in the bandwidth-controlled organic conductor κ-(BEDT-TTF)2Cu[N(CN)2]Br. In addition to reviewing SMIS of the phase separation, we briefly mention the electronic and optical properties of κ-(BEDT-TTF)2X.
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Affiliation(s)
- Takahiko Sasaki
- Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
- JST, CREST, Sanbancho 5, Chiyoda-ku, Tokyo 102-0075, Japan
| | - Naoki Yoneyama
- Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
- JST, CREST, Sanbancho 5, Chiyoda-ku, Tokyo 102-0075, Japan
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Müller J, Brandenburg J, Schlueter JA. Magnetic-field induced crossover of superconducting percolation regimes in the layered organic Mott system kappa-(BEDT-TTF)2Cu[N(CN) 2]Cl. PHYSICAL REVIEW LETTERS 2009; 102:047004. [PMID: 19257466 DOI: 10.1103/physrevlett.102.047004] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/03/2008] [Indexed: 05/27/2023]
Abstract
Fluctuation spectroscopy is used to investigate the organic bandwidth-controlled Mott system kappa-(BEDT-TTF)(2)Cu[N(CN)(2)]Cl. We find evidence for percolative-type superconductivity in the spatially inhomogeneous coexistence region of antiferromagnetic insulating and superconducting states. When the superconducting transition is driven by a magnetic field, percolation seems to be dominated by instable superconducting clusters upon approaching T(c)(B) from above, before a "classical" type of percolation is resumed at low fields, dominated by the fractional change of superconducting clusters. The 1/f noise is resolved into Lorentzian spectra in the crossover region, where the action of an individual fluctuator is enhanced, pointing to a mesoscopic phase separation.
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Affiliation(s)
- Jens Müller
- Max Planck Institute for Chemical Physics of Solids, Nöthnitzer-Strasse 40, 01187 Dresden, Germany.
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Sasaki T, Yoneyama N, Nakamura Y, Kobayashi N, Ikemoto Y, Moriwaki T, Kimura H. Optical probe of carrier doping by X-ray irradiation in the organic dimer Mott insulator kappa-(BEDT-TTF)_{2}Cu[N(CN)_{2}]Cl. PHYSICAL REVIEW LETTERS 2008; 101:206403. [PMID: 19113361 DOI: 10.1103/physrevlett.101.206403] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/25/2008] [Indexed: 05/27/2023]
Abstract
We investigated the infrared optical spectra of an organic dimer Mott insulator kappa-(BEDT-TTF)_{2}Cu[N(CN)_{2}]Cl, which was irradiated with x rays. We observed that the irradiation caused a large spectral weight transfer from the midinfrared region, where interband transitions in the dimer and Mott-Hubbard bands take place, to a Drude part in a low-energy region; this caused the Mott gap to collapse. The increase of the Drude part indicates a carrier doping into the Mott insulator due to irradiation defects. The strong redistribution of the spectral weight demonstrates that the organic Mott insulator is very close to the phase border of the bandwidth-controlled Mott-insulator-metal transition.
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Affiliation(s)
- T Sasaki
- Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan.
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Clay RT, Li H, Mazumdar S. Absence of superconductivity in the half-filled band Hubbard model on the anisotropic triangular lattice. PHYSICAL REVIEW LETTERS 2008; 101:166403. [PMID: 18999691 DOI: 10.1103/physrevlett.101.166403] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/05/2008] [Indexed: 05/27/2023]
Abstract
We report exact calculations of magnetic and superconducting pair-pair correlations for the half-filled band Hubbard model on an anisotropic triangular lattice. Our results for the magnetic phases are similar to those obtained with other techniques. The superconducting pair-pair correlations at distances beyond nearest neighbor decrease monotonically with increasing Hubbard interaction U for all anisotropy, indicating the absence of frustration-driven superconductivity within the model.
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Affiliation(s)
- R T Clay
- Department of Physics and Astronomy and HPC2 Center for Computational Sciences, Mississippi State University, Mississippi State, MS 39762, USA
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Kanoda K. Mott Transition and Superconductivity in Q2D Organic Conductors. THE PHYSICS OF ORGANIC SUPERCONDUCTORS AND CONDUCTORS 2008. [DOI: 10.1007/978-3-540-76672-8_22] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
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34
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Saito G, Yoshida Y. Development of Conductive Organic Molecular Assemblies: Organic Metals, Superconductors, and Exotic Functional Materials. BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 2007. [DOI: 10.1246/bcsj.80.1] [Citation(s) in RCA: 341] [Impact Index Per Article: 20.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
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Kubota M, Saito G, Ito H, Ishiguro T, Kojima N. Magnetism of the Organic Superconductor κ-(BEDT-TTF)2Cu[N(CN)2]Cl. ACTA ACUST UNITED AC 2006. [DOI: 10.1080/10587259608037939] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Affiliation(s)
- Masahiro Kubota
- a Department of Chemistry, Graduate School of Science , Kyoto University , Sakyo-ku, Kyoto , 606-01 , Japan
| | - Gunzi Saito
- a Department of Chemistry, Graduate School of Science , Kyoto University , Sakyo-ku, Kyoto , 606-01 , Japan
| | - Hiroshi Ito
- b Department of Physics, Graduate School of Science , Kyoto University , Sakyo-ku, Kyoto , 606-01 , Japan
| | - Takehiko Ishiguro
- b Department of Physics, Graduate School of Science , Kyoto University , Sakyo-ku, Kyoto , 606-01 , Japan
| | - Norimichi Kojima
- c Department of Pure and Applied Sciences, Faculty of Arts and Sciences , University of Tokyo , Meguro-ku, Tokyo , 153 , Japan
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Takahide Y, Konoike T, Enomoto K, Nishimura M, Terashima T, Uji S, Yamamoto HM. Current-voltage characteristics of charge-ordered organic crystals. PHYSICAL REVIEW LETTERS 2006; 96:136602. [PMID: 16712014 DOI: 10.1103/physrevlett.96.136602] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/27/2005] [Indexed: 05/09/2023]
Abstract
The current-voltage characteristics of layered organic crystals theta-(BEDT-TTF)2MZn(SCN)4 (M = Cs, Rb) follow the power law with a large exponent (e.g., 8.4 at 0.29 K for M = Cs) over a wide range of currents in the low-temperature insulating state. The power-law characteristics are attributed to electric field-induced unbinding of electron-hole pairs that are thermally excited in the background of the two-dimensional charge order. The magnitude of crossover electric fields from Ohmic to the power-law characteristics indicates that the electron-electron Coulomb interaction is significantly long-ranged: The screening length is greater than 10 molecule sites.
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37
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Kawakami T, Taniguchi T, Shoji M, Kitagawa Y, Okumura M, Yamaguchi K. Theoretical direct evaluation of inter-dimer J values in BETS salts. Polyhedron 2005. [DOI: 10.1016/j.poly.2005.08.017] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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38
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Kurosaki Y, Shimizu Y, Miyagawa K, Kanoda K, Saito G. Mott transition from a spin liquid to a Fermi liquid in the spin-frustrated organic conductor kappa-(ET)2Cu2(CN)3. PHYSICAL REVIEW LETTERS 2005; 95:177001. [PMID: 16383857 DOI: 10.1103/physrevlett.95.177001] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/15/2004] [Revised: 04/06/2005] [Indexed: 05/05/2023]
Abstract
The pressure-temperature phase diagram of the organic Mott insulator kappa-(ET)2Cu2(CN)3, a model system of the spin liquid on triangular lattice, has been investigated by 1H NMR and resistivity measurements. The spin-liquid phase is persistent before the Mott transition to the metal or superconducting phase under pressure. At the Mott transition, the spin fluctuations are rapidly suppressed and the Fermi-liquid features are observed in the temperature dependence of the spin-lattice relaxation rate and resistivity. The characteristic curvature of the Mott boundary in the phase diagram highlights a crucial effect of the spin frustration on the Mott transition.
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Affiliation(s)
- Y Kurosaki
- Department of Applied Physics, University of Tokyo, Tokyo, 113-8656, Japan
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39
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Gan JY, Chen Y, Su ZB, Zhang FC. Gossamer superconductivity near antiferromagnetic Mott insulator in layered organic conductors. PHYSICAL REVIEW LETTERS 2005; 94:067005. [PMID: 15783770 DOI: 10.1103/physrevlett.94.067005] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/18/2004] [Indexed: 05/24/2023]
Abstract
Layered organic superconductors are on the verge of the Mott insulator. We use the Gutzwiller variational method to study a two-dimensional Hubbard model including a spin exchange coupling term as a minimal model for the compounds. The ground state is found to be a Gossamer superconductor at small on-site Coulomb repulsion U and an antiferromagnetic Mott insulator at large U, separated by a first order phase transition. Our theory is qualitatively consistent with major experiments reported in organic superconductors.
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Affiliation(s)
- J Y Gan
- Institute for Theoretical Physics, Chinese Academy of Sciences, Beijing, 100080, China
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Miyagawa K, Kanoda K, Kawamoto A. NMR Studies on Two-Dimensional Molecular Conductors and Superconductors: Mott Transition in κ-(BEDT-TTF)2X. Chem Rev 2004; 104:5635-54. [PMID: 15535663 DOI: 10.1021/cr0306541] [Citation(s) in RCA: 126] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Kazuya Miyagawa
- Department of Applied Physics, University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo 113-8656, Japan
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Seo H, Hotta C, Fukuyama H. Toward Systematic Understanding of Diversity of Electronic Properties in Low-Dimensional Molecular Solids. Chem Rev 2004; 104:5005-36. [PMID: 15535640 DOI: 10.1021/cr030646k] [Citation(s) in RCA: 331] [Impact Index Per Article: 16.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Hitoshi Seo
- Correlated Electron Research Center (CERC), AIST Tsukuba Central 4, Ibaraki 305-8562, Japan
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Smith DF, Slichter CP, Schlueter JA, Kini AM, Daugherty RG. Precise determination of the orientation of the Dzialoshinskii-Moriya vector in kappa-(BEDT-TTF)2Cu[N(CN)(2)]Cl. PHYSICAL REVIEW LETTERS 2004; 93:167002. [PMID: 15525021 DOI: 10.1103/physrevlett.93.167002] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/10/2004] [Indexed: 05/24/2023]
Abstract
A novel electron spin-reorientation transition is discovered by 13C NMR in the quasi-two-dimensional organic antiferromagnet kappa-(BEDT-TTF)(2)Cu[N(CN)(2)]Cl. The spin reorientation occurs as an external field is swept through the orientation of the characteristic vector of the Dzialoshinskii-Moriya (DM) interaction, thus providing a precise determination of the orientation of the DM vector. Such a spin reorientation could help to characterize the DM interaction in other antiferromagnetic systems.
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Affiliation(s)
- Dylan F Smith
- Department of Physics, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA.
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Kagawa F, Itou T, Miyagawa K, Kanoda K. Magnetic-field-induced Mott transition in a quasi-two-dimensional organic conductor. PHYSICAL REVIEW LETTERS 2004; 93:127001. [PMID: 15447299 DOI: 10.1103/physrevlett.93.127001] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/01/2004] [Indexed: 05/24/2023]
Abstract
We investigated the effect of magnetic field on the highly correlated metal near the Mott transition in the quasi-two-dimensional layered organic conductor, kappa-(BEDT-TTF)(2)Cu[N(CN)(2)]Cl, by the resistance measurements under control of temperature, pressure, and magnetic field. It was demonstrated that the marginal metallic phase near the Mott transition is susceptible to the field-induced localization transition of the first order, as was predicted theoretically. The thermodynamic consideration of the present results gives a conceptual pressure-field phase diagram of the Mott transition at low temperatures.
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Affiliation(s)
- F Kagawa
- Department of Applied Physics, University of Tokyo, Bunkyo-ku, Tokyo 113-8656, Japan
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Coulon C, Clérac R. Electron Spin Resonance: A Major Probe for Molecular Conductors. Chem Rev 2004; 104:5655-88. [PMID: 15535664 DOI: 10.1021/cr030639w] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Claude Coulon
- Centre de Recherche Paul Pascal, CNRS UPR 8641, Université Bordeaux 1, 115 Avenue Dr. A. Schweitzer, 33600 Pessac, France.
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Shimizu Y, Miyagawa K, Kanoda K, Maesato M, Saito G. Spin liquid state in an organic Mott insulator with a triangular lattice. PHYSICAL REVIEW LETTERS 2003; 91:107001. [PMID: 14525498 DOI: 10.1103/physrevlett.91.107001] [Citation(s) in RCA: 272] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/15/2002] [Revised: 07/07/2003] [Indexed: 05/24/2023]
Abstract
1H NMR and static susceptibility measurements have been performed in an organic Mott insulator with a nearly isotropic triangular lattice, kappa-(BEDT-TTF)2Cu2(CN)(3), which is a model system of frustrated quantum spins. The static susceptibility is described by the spin S=1/2 antiferromagnetic triangular-lattice Heisenberg model with the exchange constant J approximately 250 K. Regardless of the large magnetic interactions, the 1H NMR spectra show no indication of long-range magnetic ordering down to 32 mK, which is 4 orders of magnitude smaller than J. These results suggest that a quantum spin liquid state is realized in the close proximity of the superconducting state appearing under pressure.
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Affiliation(s)
- Y Shimizu
- Division of Chemistry, Graduate School of Science, Kyoto University, Oiwaketyo, Kitashirakawa, Sakyo-ku, Kyoto, 606-8502, Japan
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Yamaguchi K, Kawakami T, Taniguchi T, Nakano S, Kitagawa Y, Nagao H, Ohsaku T, Takeda R. Theoretical studies of molecule-based magnetic conductors. Polyhedron 2003. [DOI: 10.1016/s0277-5387(03)00295-x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Kawakami T, Taniguchi T, Nakano S, Kitagawa Y, Yamaguchi K. Theoretical studies on magnetic interactions in many types of organic donor salts: BEDT-TTF, BETS, TMTTF and TMTSF. Polyhedron 2003. [DOI: 10.1016/s0277-5387(03)00298-5] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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48
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KAWAKAMI TAKASHI, TANIGUCHI TAKESHI, KITAGAWA YASUTAKA, TAKANO YU, NAGAO HIDEMI, YAMAGUCHI KIZASHI. Theoretical investigation of magnetic parameters in two-dimensional sheets of pure organic BEDT-TTF and BETS molecules by usingab initioMO and DFT methods. Mol Phys 2002. [DOI: 10.1080/00268970210136366] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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Miyagawa K, Kawamoto A, Kanoda K. Proximity of pseudogapped superconductor and commensurate antiferromagnet in a quasi-two-dimensional organic system. PHYSICAL REVIEW LETTERS 2002; 89:017003. [PMID: 12097066 DOI: 10.1103/physrevlett.89.017003] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/16/2001] [Indexed: 05/23/2023]
Abstract
We performed the single-crystal 13C NMR studies on a quasi-two-dimensional system, deuterated kappa-(BEDT-TTF)2Cu[N(CN)(2)]Br, which is just on the border of the Mott transition. The NMR spectra are separated into two parts coming from the metallic (superconducting) and insulating phases due to the phase separation at low temperature. The examination of the separated spectra revealed that the Mott transition in this system is characterized by the first-order transition between the pseudogapped superconductor and the simplest commensurate antiferromagnet with a moment of 0.26 mu(B)/dimer.
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Affiliation(s)
- K Miyagawa
- Department of Applied Physics, University of Tokyo, Bunkyo-ku, Tokyo 113-8656, Japan
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Yamaguchi K, Kitagawa Y, Onishi T, Isobe H, Kawakami T, Nagao H, Takamizawa S. Spin-mediated superconductivity in cuprates, organic conductors and π–d conjugated systems. Coord Chem Rev 2002. [DOI: 10.1016/s0010-8545(01)00440-4] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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