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Li Y, Gegenwart P, Tsirlin AA. Spin liquids in geometrically perfect triangular antiferromagnets. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2020; 32:224004. [PMID: 32015221 DOI: 10.1088/1361-648x/ab724e] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
The cradle of quantum spin liquids, triangular antiferromagnets show strong proclivity to magnetic order and require deliberate tuning to stabilize a spin-liquid state. In this brief review, we juxtapose recent theoretical developments that trace the parameter regime of the spin-liquid phase, with experimental results for Co-based and Yb-based triangular antiferromagnets. Unconventional spin dynamics arising from both ordered and disordered ground states are discussed, and the notion of a geometrically perfect triangular system is scrutinized to demonstrate non-trivial imperfections that may assist magnetic frustration in stabilizing dynamic spin states with peculiar excitations.
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Affiliation(s)
- Yuesheng Li
- Experimental Physics VI, Center for Electronic Correlations and Magnetism, University of Augsburg, 86159 Augsburg, Germany. Wuhan National High Magnetic Field Center and School of Physics, Huazhong University of Science and Technology, 430074 Wuhan, People's Republic of China
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2
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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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Schlawin F, Cavalleri A, Jaksch D. Cavity-Mediated Electron-Photon Superconductivity. PHYSICAL REVIEW LETTERS 2019; 122:133602. [PMID: 31012600 DOI: 10.1103/physrevlett.122.133602] [Citation(s) in RCA: 53] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/21/2018] [Revised: 02/06/2019] [Indexed: 05/03/2023]
Abstract
We investigate electron paring in a two-dimensional electron system mediated by vacuum fluctuations inside a nanoplasmonic terahertz cavity. We show that the structured cavity vacuum can induce long-range attractive interactions between current fluctuations which lead to pairing in generic materials with critical temperatures in the low-kelvin regime for realistic parameters. The induced state is a pair-density wave superconductor which can show a transition from a fully gapped to a partially gapped phase-akin to the pseudogap phase in high-T_{c} superconductors. Our findings provide a promising tool for engineering intrinsic electron interactions in two-dimensional materials.
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Affiliation(s)
- Frank Schlawin
- Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX1 3PU, United Kingdom
| | - Andrea Cavalleri
- Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX1 3PU, United Kingdom
- Max Planck Institute for the Structure and Dynamics of Matter, Luruper Chaussee 149, 22761 Hamburg, Germany
| | - Dieter Jaksch
- Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX1 3PU, United Kingdom
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4
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Hickey C, Trebst S. Emergence of a field-driven U(1) spin liquid in the Kitaev honeycomb model. Nat Commun 2019; 10:530. [PMID: 30705263 PMCID: PMC6355955 DOI: 10.1038/s41467-019-08459-9] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2018] [Accepted: 01/08/2019] [Indexed: 11/30/2022] Open
Abstract
In the field of quantum magnetism, the exactly solvable Kitaev honeycomb model serves as a paradigm for the fractionalization of spin degrees of freedom and the formation of \documentclass[12pt]{minimal}
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\begin{document}$${\Bbb Z}_2$$\end{document}Z2 quantum spin liquids. An intense experimental search has led to the discovery of a number of spin-orbit entangled Mott insulators that realize its characteristic bond-directional interactions and, in the presence of magnetic fields, exhibit no indications of long-range order. Here, we map out the complete phase diagram of the Kitaev model in tilted magnetic fields and report the emergence of a distinct gapless quantum spin liquid at intermediate field strengths. Analyzing a number of static, dynamical, and finite temperature quantities using numerical exact diagonalization techniques, we find strong evidence that this phase exhibits gapless fermions coupled to a massless U(1) gauge field. We discuss its stability in the presence of perturbations that naturally arise in spin-orbit entangled candidate materials. The Kitaev model is intensively studied as an exactly-solvable starting point for theoretical studies of quantum spin liquid states. Hickey and Trebst show that magnetic fields can destabilize the well-known gapped Kitaev spin liquid and induce a new gapless spin liquid, with a distinct gauge structure and neutral Fermi surface.
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Affiliation(s)
- Ciarán Hickey
- Institute for Theoretical Physics, University of Cologne, 50937, Cologne, Germany.
| | - Simon Trebst
- Institute for Theoretical Physics, University of Cologne, 50937, Cologne, Germany
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Isono T, Sugiura S, Terashima T, Miyagawa K, Kanoda K, Uji S. Spin-lattice decoupling in a triangular-lattice quantum spin liquid. Nat Commun 2018; 9:1509. [PMID: 29666404 PMCID: PMC5904176 DOI: 10.1038/s41467-018-04005-1] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2017] [Accepted: 03/27/2018] [Indexed: 11/10/2022] Open
Abstract
A quantum spin liquid (QSL) is an exotic state of matter in condensed-matter systems, where the electron spins are strongly correlated, but conventional magnetic orders are suppressed down to zero temperature because of strong quantum fluctuations. One of the most prominent features of a QSL is the presence of fractionalized spin excitations, called spinons. Despite extensive studies, the nature of the spinons is still highly controversial. Here we report magnetocaloric-effect measurements on an organic spin-1/2 triangular-lattice antiferromagnet, showing that electron spins are decoupled from a lattice in a QSL state. The decoupling phenomena support the gapless nature of spin excitations. We further find that as a magnetic field is applied away from a quantum critical point, the number of spin states that interact with lattice vibrations is strongly reduced, leading to weak spin–lattice coupling. The results are compared with a model of a strongly correlated QSL near a quantum critical point. A number of materials have been proposed as realizations of exotic quantum spin liquids but many important properties are difficult to establish. Isono et al. show evidence for spin-lattice decoupling in an organic material, which may help resolve conflicting results about the existence of a spin-excitation gap.
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Affiliation(s)
- Takayuki Isono
- National Institute for Materials Science, Tsukuba, Ibaraki, 305-0003, Japan. .,Condensed Molecular Materials Laboratory, RIKEN, Wako, Saitama, 351-0198, Japan.
| | - Shiori Sugiura
- National Institute for Materials Science, Tsukuba, Ibaraki, 305-0003, Japan
| | - Taichi Terashima
- National Institute for Materials Science, Tsukuba, Ibaraki, 305-0003, Japan
| | - Kazuya Miyagawa
- Department of Applied Physics, University of Tokyo, Bunkyo-ku, Tokyo, 113-8656, Japan
| | - Kazushi Kanoda
- Department of Applied Physics, University of Tokyo, Bunkyo-ku, Tokyo, 113-8656, Japan
| | - Shinya Uji
- National Institute for Materials Science, Tsukuba, Ibaraki, 305-0003, Japan.
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Low-Temperature Lattice Effects in the Spin-Liquid Candidate κ-(BEDT-TTF)2Cu2(CN)3. CRYSTALS 2018. [DOI: 10.3390/cryst8020087] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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7
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Gomilšek M, Klanjšek M, Žitko R, Pregelj M, Bert F, Mendels P, Li Y, Zhang QM, Zorko A. Field-Induced Instability of a Gapless Spin Liquid with a Spinon Fermi Surface. PHYSICAL REVIEW LETTERS 2017; 119:137205. [PMID: 29341713 DOI: 10.1103/physrevlett.119.137205] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/17/2017] [Indexed: 06/07/2023]
Abstract
The ground state of the quantum kagome antiferromagnet Zn-brochantite, ZnCu_{3}(OH)_{6}SO_{4}, which is one of only a few known spin-liquid (SL) realizations in two or three dimensions, has been described as a gapless SL with a spinon Fermi surface. Employing nuclear magnetic resonance in a broad magnetic-field range down to millikelvin temperatures, we show that in applied magnetic fields this enigmatic state is intrinsically unstable against a SL with a full or a partial gap. A similar instability of the gapless Fermi-surface SL was previously encountered in an organic triangular-lattice antiferromagnet, suggesting a common destabilization mechanism that most likely arises from spinon pairing. A salient property of this instability is that an infinitesimal field suffices to induce it, as predicted theoretically for some other types of gapless SLs.
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Affiliation(s)
- M Gomilšek
- Jožef Stefan Institute, Jamova c. 39, SI-1000 Ljubljana, Slovenia
| | - M Klanjšek
- Jožef Stefan Institute, Jamova c. 39, SI-1000 Ljubljana, Slovenia
| | - R Žitko
- Jožef Stefan Institute, Jamova c. 39, SI-1000 Ljubljana, Slovenia
| | - M Pregelj
- Jožef Stefan Institute, Jamova c. 39, SI-1000 Ljubljana, Slovenia
| | - F Bert
- Laboratoire de Physique des Solides, CNRS, Univ. Paris-Sud, Université Paris-Saclay, 91405 Orsay, Cedex, France
| | - P Mendels
- Laboratoire de Physique des Solides, CNRS, Univ. Paris-Sud, Université Paris-Saclay, 91405 Orsay, Cedex, France
| | - Y Li
- Department of Physics, Renmin University of China, Beijing 100872, People's Republic of China
| | - Q M Zhang
- Department of Physics, Renmin University of China, Beijing 100872, People's Republic of China
- Department of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240 and Collaborative Innovation Center of Advanced Microstructures, Nanjing 210093, People's Republic of China
| | - A Zorko
- Jožef Stefan Institute, Jamova c. 39, SI-1000 Ljubljana, Slovenia
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8
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Powell BJ, Kenny EP, Merino J. Dynamical Reduction of the Dimensionality of Exchange Interactions and the "Spin-Liquid" Phase of κ-(BEDT-TTF)_{2}X. PHYSICAL REVIEW LETTERS 2017; 119:087204. [PMID: 28952764 DOI: 10.1103/physrevlett.119.087204] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/19/2017] [Indexed: 06/07/2023]
Abstract
We show that the anisotropy of the effective spin model for the dimer Mott insulator phase of κ-(BEDT-TTF)_{2}X salts is dramatically different from that of the underlying tight-binding model. Intradimer quantum interference results in a model of coupled spin chains, where frustrated interchain interactions suppress long-range magnetic order. Thus, we argue, the "spin liquid" phase observed in some of these materials is a remnant of the Tomonaga-Luttinger physics of a single chain. This is consistent with previous experiments and resolves some outstanding puzzles.
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Affiliation(s)
- B J Powell
- School of Mathematics and Physics, The University of Queensland, Brisbane, Queensland 4072, Australia
| | - E P Kenny
- School of Mathematics and Physics, The University of Queensland, Brisbane, Queensland 4072, Australia
| | - J Merino
- Departamento de Física Teórica de la Materia Condensada, Condensed Matter Physics Center (IFIMAC) and Instituto Nicolás Cabrera, Universidad Autónoma de Madrid, Madrid 28049, Spain
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9
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Shimizu Y, Hiramatsu T, Maesato M, Otsuka A, Yamochi H, Ono A, Itoh M, Yoshida M, Takigawa M, Yoshida Y, Saito G. Pressure-Tuned Exchange Coupling of a Quantum Spin Liquid in the Molecular Triangular Lattice κ-(ET)_{2}Ag_{2}(CN)_{3}. PHYSICAL REVIEW LETTERS 2016; 117:107203. [PMID: 27636491 DOI: 10.1103/physrevlett.117.107203] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/05/2016] [Indexed: 06/06/2023]
Abstract
The effects of pressure on a quantum spin liquid are investigated in an organic Mott insulator κ-(ET)_{2}Ag_{2}(CN)_{3} with a spin-1/2 triangular lattice. The application of negative chemical pressure to κ-(ET)_{2}Cu_{2}(CN)_{3}, which is a well-known sister Mott insulator, allows for extensive tuning of antiferromagnetic exchange coupling, with J/k_{B}=175-310 K, under hydrostatic pressure. Based on ^{13}C nuclear magnetic resonance measurements under pressure, we uncover universal scaling in the static and dynamic spin susceptibilities down to low temperatures ∼0.1k_{B}T/J. The persistent fluctuations and residual specific heat coefficient are consistent with the presence of gapless low-lying excitations. Our results thus demonstrate the fundamental finite-temperature properties of a quantum spin liquid in a wide parameter range.
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Affiliation(s)
- Yasuhiro Shimizu
- Department of Physics, Nagoya University, Chikusa, Nagoya 464-8602, Japan
| | - Takaaki Hiramatsu
- Faculty of Agriculture, Meijo University, Tempaku-ku, Nagoya 468-8502, Japan
| | - Mitsuhiko Maesato
- Division of Chemistry, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan
| | - Akihiro Otsuka
- Division 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
| | - Hideki Yamochi
- Division 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
| | - Akihiro Ono
- Department of Physics, Nagoya University, Chikusa, Nagoya 464-8602, Japan
| | - Masayuki Itoh
- Department of Physics, Nagoya University, Chikusa, Nagoya 464-8602, Japan
| | - Makoto Yoshida
- Institute for Solid State Physics, University of Tokyo, Kashiwa, Chiba 277-8581, Japan
| | - Masashi Takigawa
- Institute for Solid State Physics, University of Tokyo, Kashiwa, Chiba 277-8581, Japan
| | - Yukihiro Yoshida
- Faculty of Agriculture, Meijo University, Tempaku-ku, Nagoya 468-8502, Japan
| | - Gunzi Saito
- Faculty of Agriculture, Meijo University, Tempaku-ku, Nagoya 468-8502, Japan
- Toyota Physical and Chemical Research Institute, Nagakute, Aichi 480-1192, Japan
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10
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Kargarian M, Efimkin DK, Galitski V. Amperean Pairing at the Surface of Topological Insulators. PHYSICAL REVIEW LETTERS 2016; 117:076806. [PMID: 27563988 DOI: 10.1103/physrevlett.117.076806] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/24/2016] [Indexed: 06/06/2023]
Abstract
The surface of a 3D topological insulator is described by a helical electron state with the electron's spin and momentum locked together. We show that in the presence of ferromagnetic fluctuations the surface of a topological insulator is unstable towards a superconducting state with unusual pairing, dubbed Amperean pairing. The key idea is that the dynamical fluctuations of a ferromagnetic layer deposited on the surface of a topological insulator couple to the electrons as gauge fields. The transverse components of the magnetic gauge fields are unscreened and can mediate an effective interaction between electrons. There is an attractive interaction between electrons with momenta in the same direction which makes the pairing to be of Amperean type. We show that this attractive interaction leads to a p-wave pairing instability of the Fermi surface in the Cooper channel.
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Affiliation(s)
- Mehdi Kargarian
- Joint Quantum Institute and Condensed Matter Theory Center, Department of Physics, University of Maryland, College Park, Maryland 20742-4111, USA
| | - Dmitry K Efimkin
- Joint Quantum Institute and Condensed Matter Theory Center, Department of Physics, University of Maryland, College Park, Maryland 20742-4111, USA
| | - Victor Galitski
- Joint Quantum Institute and Condensed Matter Theory Center, Department of Physics, University of Maryland, College Park, Maryland 20742-4111, USA
- School of Physics, Monash University, Melbourne, Victoria 3800, Australia
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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: 20] [Impact Index Per Article: 2.2] [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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12
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Isono T, Kamo H, Ueda A, Takahashi K, Kimata M, Tajima H, Tsuchiya S, Terashima T, Uji S, Mori H. Gapless quantum spin liquid in an organic spin-1/2 triangular-lattice κ-H3(Cat-EDT-TTF)2. PHYSICAL REVIEW LETTERS 2014; 112:177201. [PMID: 24836269 DOI: 10.1103/physrevlett.112.177201] [Citation(s) in RCA: 63] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/09/2013] [Indexed: 06/03/2023]
Abstract
We report the results of SQUID and torque magnetometry of an organic spin-1/2 triangular-lattice κ-H(3)(Cat-EDT-TTF)(2). Despite antiferromagnetic exchange coupling at 80-100 K, we observed no sign of antiferromagnetic order down to 50 mK owing to spin frustration on the triangular lattice. In addition, we found nearly temperature-independent susceptibility below 3 K associated with Pauli paramagnetism. These observations suggest the development of gapless quantum spin liquid as the ground state. On the basis of a comparative discussion, we point out that the gapless quantum spin liquid states in organic systems share a possible mechanism, namely the formation of a band with a Fermi surface possibly attributed to spinons.
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Affiliation(s)
- Takayuki Isono
- The Institute for Solid State Physics (ISSP), The University of Tokyo, Kashiwa, Chiba 277-8581, Japan
| | - Hiromichi Kamo
- The Institute for Solid State Physics (ISSP), The University of Tokyo, Kashiwa, Chiba 277-8581, Japan
| | - Akira Ueda
- The Institute for Solid State Physics (ISSP), The University of Tokyo, Kashiwa, Chiba 277-8581, Japan
| | | | - Motoi Kimata
- The Institute for Solid State Physics (ISSP), The University of Tokyo, Kashiwa, Chiba 277-8581, Japan
| | - Hiroyuki Tajima
- The Institute for Solid State Physics (ISSP), The University of Tokyo, Kashiwa, Chiba 277-8581, Japan
| | - Satoshi Tsuchiya
- National Institute for Materials Science, Tsukuba, Ibaraki 305-0003, Japan
| | - Taichi Terashima
- National Institute for Materials Science, Tsukuba, Ibaraki 305-0003, Japan
| | - Shinya Uji
- National Institute for Materials Science, Tsukuba, Ibaraki 305-0003, Japan
| | - Hatsumi Mori
- The Institute for Solid State Physics (ISSP), The University of Tokyo, Kashiwa, Chiba 277-8581, Japan
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Watanabe D, Yamashita M, Tonegawa S, Oshima Y, Yamamoto HM, Kato R, Sheikin I, Behnia K, Terashima T, Uji S, Shibauchi T, Matsuda Y. Novel Pauli-paramagnetic quantum phase in a Mott insulator. Nat Commun 2013; 3:1090. [PMID: 23011144 DOI: 10.1038/ncomms2082] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2012] [Accepted: 08/22/2012] [Indexed: 11/09/2022] Open
Abstract
In Mott insulators, the strong electron-electron Coulomb repulsion localizes electrons. In dimensions greater than one, their spins are usually ordered antiferromagnetically at low temperatures. Geometrical frustrations can destroy this long-range order, leading to exotic quantum spin liquid states. However, their magnetic ground states have been a long-standing mystery. Here we show that a quantum spin liquid state in the organic Mott insulator EtMe(3)Sb[Pd(dmit)(2)](2) (where Et is C(2)H(5)-, Me is CH(3)-, and dmit is 1,3-dithiole-2-thione-4,5-dithiolate) with two-dimensional triangular lattice has Pauli-paramagnetic-like low-energy excitations, which are a hallmark of itinerant fermions. Our torque magnetometry down to low temperatures (30 mK) up to high fields (32 T) reveals distinct residual paramagnetic susceptibility comparable to that in a half-filled two-dimensional metal, demonstrating the magnetically gapless nature of the ground state. Moreover, our results are robust against deuteration, pointing toward the emergence of an extended 'quantum critical phase', in which low-energy spin excitations behave as in paramagnetic metals with Fermi surface, despite the frozen charge degree of freedom.
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Affiliation(s)
- D Watanabe
- Department of Physics, Kyoto University, Kyoto 606-8502, Japan
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14
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Magnetic and non-magnetic phases of a quantum spin liquid. Nature 2011; 471:612-6. [DOI: 10.1038/nature09910] [Citation(s) in RCA: 143] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2010] [Accepted: 02/07/2011] [Indexed: 11/08/2022]
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Itou T, Oyamada A, Maegawa S, Tamura M, Kato R. 13C NMR study of the spin-liquid state in the triangular quantum antiferromagnet EtMe3Sb[Pd(dmit)2]2. ACTA ACUST UNITED AC 2009. [DOI: 10.1088/1742-6596/145/1/012039] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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