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Riedl K, Gati E, Zielke D, Hartmann S, Vyaselev OM, Kushch ND, Jeschke HO, Lang M, Valentí R, Kartsovnik MV, Winter SM. Spin Vortex Crystal Order in Organic Triangular Lattice Compound. PHYSICAL REVIEW LETTERS 2021; 127:147204. [PMID: 34652199 DOI: 10.1103/physrevlett.127.147204] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/14/2021] [Accepted: 08/25/2021] [Indexed: 06/13/2023]
Abstract
Organic salts represent an ideal experimental playground for studying the interplay between magnetic and charge degrees of freedom, which has culminated in the discovery of several spin-liquid candidates such as κ-(ET)_{2}Cu_{2}(CN)_{3} (κ-Cu). Recent theoretical studies indicate the possibility of chiral spin liquids stabilized by ring exchange, but the parent states with chiral magnetic order have not been observed in this material family. In this Letter, we discuss the properties of the recently synthesized κ-(BETS)_{2}Mn[N(CN)_{2}]_{3} (κ-Mn). Based on analysis of specific heat, magnetic torque, and NMR measurements combined with ab initio calculations, we identify a spin-vortex crystal order. These observations definitively confirm the importance of ring exchange in these materials and support the proposed chiral spin-liquid scenario for triangular lattice organics.
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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
| | - Elena Gati
- Physikalisches Institut, Goethe-Universität Frankfurt, Max von Laue Str 1, 60438 Frankfurt am Main, Germany
- Max Planck Institute for Chemical Physics of Solids, 01187 Dresden, Germany
| | - David Zielke
- Physikalisches Institut, Goethe-Universität Frankfurt, Max von Laue Str 1, 60438 Frankfurt am Main, Germany
| | - Steffi Hartmann
- Physikalisches Institut, Goethe-Universität Frankfurt, Max von Laue Str 1, 60438 Frankfurt am Main, Germany
| | - Oleg M Vyaselev
- Institute of Solid State Physics, Russian Academy of Sciences, 142432 Chernogolovka, Russia
| | - Nataliya D Kushch
- Institute of Problems of Chemical Physics, Russian Academy of Sciences, 142432 Chernogolovka, Russia
| | - Harald O Jeschke
- Research Institute for Interdisciplinary Science, Okayama University, Okayama 700-8530, Japan
| | - Michael Lang
- Physikalisches Institut, Goethe-Universität Frankfurt, Max von Laue Str 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
| | - Mark V Kartsovnik
- Walther-Meissner-Institut, Bayerische Akademie der Wissenschaften, Walther-Meissner-Strasse 8, Garching D-85748, Germany
| | - Stephen M Winter
- Department of Physics and Center for Functional Materials, Wake Forest University, Winston-Salem, North Carolina 27109, USA
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Furukawa T, Kobashi K, Kurosaki Y, Miyagawa K, Kanoda K. Quasi-continuous transition from a Fermi liquid to a spin liquid in κ-(ET) 2Cu 2(CN) 3. Nat Commun 2018; 9:307. [PMID: 29358740 PMCID: PMC5778024 DOI: 10.1038/s41467-017-02679-7] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2017] [Accepted: 12/18/2017] [Indexed: 11/10/2022] Open
Abstract
The Mott metal-insulator transition—a manifestation of Coulomb interactions among electrons—is known as a discontinuous transition. Recent theoretical studies, however, suggest that the transition is continuous if the Mott insulator carries a spin liquid with a spinon Fermi surface. Here, we demonstrate the case of a quasi-continuous Mott transition from a Fermi liquid to a spin liquid in an organic triangular-lattice system κ-(ET)2Cu2(CN)3. Transport experiments performed under fine pressure tuning have found that as the Mott transition is approached, the Fermi liquid coherence temperature continuously falls to the scale of kelvins, with a divergent quasi-particle decay rate on the metal side, and the charge gap continuously closes on the insulator side. A Clausius-Clapeyron analysis provides thermodynamic evidence for the extremely weak first-order nature of the transition. These results provide additional support for the existence of a spinon Fermi surface, which becomes an electron Fermi surface when charges are delocalized. Several organic materials exhibit spin liquid phases, which are predicted to host exotic spinon excitations that emerge from non-local quantum effects. Here, the authors identify a quasi-continuous phase transition in κ-(ET)2Cu2(CN)3 that may be associated with the presence of spinons.
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Affiliation(s)
- Tetsuya Furukawa
- Department of Applied Physics, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan. .,Department of Applied Physics, Tokyo University of Science, Niijyuku 6-3-1, Katsushika-ku, Tokyo, 125-8585, Japan.
| | - Kazuhiko Kobashi
- Department of Applied Physics, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan
| | - Yosuke Kurosaki
- Department of Applied Physics, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan
| | - Kazuya Miyagawa
- Department of Applied Physics, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan
| | - Kazushi Kanoda
- Department of Applied Physics, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan.
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Sorai M, Nakazawa Y, Nakano M, Miyazaki Y. Update 1 of: Calorimetric Investigation of Phase Transitions Occurring in Molecule-Based Magnets. Chem Rev 2013; 113:PR41-122. [DOI: 10.1021/cr300156s] [Citation(s) in RCA: 87] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Michio Sorai
- Research Center for Structural Thermodynamics, Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043, Japan
| | - Yasuhiro Nakazawa
- Research Center for Structural Thermodynamics, Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043, Japan
- Department of Chemistry, Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043, Japan
| | - Motohiro Nakano
- Department of Applied Chemistry,
Graduate School of Engineering, Osaka University, Suita, Osaka 565-0871,
Japan
| | - Yuji Miyazaki
- Research Center for Structural Thermodynamics, Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043, Japan
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Thermodynamic Properties of κ-(BEDT-TTF)2X Salts: Electron Correlations and Superconductivity. CRYSTALS 2012. [DOI: 10.3390/cryst2030741] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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Tokumoto M, Kinoshita N, Tanaka Y, Anzai H. Superconductivity of κ-(BEDT–TTF)2 Cu[N(CN) 2]Br: Isotope Effect Revisited. ACTA ACUST UNITED AC 2011. [DOI: 10.1557/proc-488-903] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
AbstractIn 1991, we reported a normal isotope effect in organic superconductor κ-(BEDT–TTF)2Cu[N(CN)2]Br, when all the hydrogen atoms of BEDT – TTF were replaced with deuterium. In other words, Tc was depressed by as much as 0.9 K, in contrast to the “inverse isotope effect” commonly observed in 10K-class organic superconductors. Recently, it was reported that the deuterated κ-(BEDT–TTF)2Cu[N(CN)2]Br shows an insulating nature when cooled very rapidly. Therefore, it is necessary for us to reexamine the superconducting transition of both deuterated and undeuterated κ- (BEDT – TTF)2Cu[N(CN)2]Br by SQUID measurements with special attention to the cooling speed. We studied the effect of cooling rate ranging from 10 K/min down to as slow as 0.02 K/min, and observed a significant effect not only on the superconducting transition temperature Tc but also on the superconducting volume fraction.
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Bartosch L, de Souza M, Lang M. Scaling theory of the mott transition and breakdown of the Grüneisen scaling near a finite-temperature critical end point. PHYSICAL REVIEW LETTERS 2010; 104:245701. [PMID: 20867311 DOI: 10.1103/physrevlett.104.245701] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/28/2010] [Indexed: 05/29/2023]
Abstract
We discuss a scaling theory of the lattice response in the vicinity of a finite-temperature critical end point. The thermal expansivity is shown to be more singular than the specific heat such that the Grüneisen ratio diverges as the critical point is approached, except for its immediate vicinity. More generally, we express the thermal expansivity in terms of a scaling function which we explicitly evaluate for the two-dimensional Ising universality class. Recent thermal expansivity measurements on the layered organic conductor κ-(BEDT-TTF)2X close to the Mott transition are well described by our theory.
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Affiliation(s)
- Lorenz Bartosch
- Institut für Theoretische Physik, Goethe-Universität, 60438 Frankfurt am Main, Germany
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Okuma K, Yamashita S, Nakazawa Y, Oguni M, Miyagawa K, Kanoda K. Spin ordering and enhancement of electronic heat capacity in an organic system of (DI-DCNQI)(2)(Ag(1-x)Cu(x)). JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2009; 21:015602. [PMID: 21817227 DOI: 10.1088/0953-8984/21/1/015602] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Thermodynamic measurements on the organic system of (DI-DCNQI)(2)(Ag(1-x)Cu(x)) (x = 0,0.05, 0.71, 0.90) were performed to study the change from the charge-ordered (CO) insulating state to the π-d hybridized metallic state. A thermal anomaly associated with the antiferromagnetic transition that occurred in the charge-ordered lattice was observed at 6.2 K from the temperature dependence of the heat capacity of (DI-DCNQI)(2)Ag. We have found that the magnetic entropy around the peak is only 1.5% of Rln2, corresponding to the full entropy expected for the formula unit of (DI-DCNQI)(2)Ag. This anomaly is suppressed down to about 3 K in the x = 0.05 sample owing to the disorders induced in the CO lattice. In the metallic concentration of x = 0.90, the low-temperature electronic heat capacity coefficient, γ was found to be enhanced by up to about 63.6 mJ K(-2) mol(-1) probably owing to the cooperative effect of π-d hybridization and intersite Coulomb interaction (V).
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Affiliation(s)
- K Okuma
- Department of Chemistry, Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043, Japan. Department of Chemistry, Graduate School of Science and Engineering, Tokyo Institute of Technology, Meguro-Ku, Tokyo 152-8550, Japan
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Nakazawa Y, Seki M, Saito K, Hiraki KI, Takahashi T, Kanoda K, Sorai M. Thermodynamic investigation of the charge-ordered insulating state of the quasi-one-dimensional organic system (DI-DCNQI)2Ag. PHYSICAL REVIEW LETTERS 2002; 88:076402. [PMID: 11863923 DOI: 10.1103/physrevlett.88.076402] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/06/2001] [Indexed: 05/23/2023]
Abstract
Heat capacity measurements of a charge-ordered organic conductor (DI-DCNQI)2Ag have been performed in a temperature range between 0.3 and 14 K. We found no thermal anomaly at the Néel temperature ( T(N) = 5.5 K) but instead a T-linear term suggestive of the spin excitations of one-dimensional character in the charge-ordered insulating state. The analysis of the T-linear term and the excess entropy indicates that the charge fluctuations in the charge-ordered state influence the growth of spin excitations at elevated temperatures, which seems to be a peculiar aspect of a 1D charge-ordered system.
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Affiliation(s)
- Yasuhiro Nakazawa
- Research Center for Molecular Thermodynamics, Osaka University, Machikaneyama 1-1, Toyonaka, Osaka 560-0043, Japan
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Elsinger H, Wosnitza J, Wanka S, Hagel J, Schweitzer D, Strunz W. kappa-(BEDT-TTF)2Cu[N(CN)(2)]Br: a fully gapped strong-coupling superconductor. PHYSICAL REVIEW LETTERS 2000; 84:6098-6101. [PMID: 10991133 DOI: 10.1103/physrevlett.84.6098] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/03/1999] [Indexed: 05/23/2023]
Abstract
High-resolution specific-heat measurements of the organic superconductor kappa-(BEDT-TTF)(2)-Cu[N(CN)(2)]Br in the superconducting ( B = 0) and normal ( B = 14 T) states show a clearly resolvable anomaly at T(c) = 11.5 K and an electronic contribution, C(es), which can be reasonably well described by strong-coupling BCS theory. Most importantly, C(es) vanishes exponentially in the superconducting state which gives evidence for a fully gapped order parameter.
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Affiliation(s)
- H Elsinger
- Physikalisches Institut, Universität Karlsruhe, 76128 Karlsruhe, Germany
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