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Tafra E, Basletić M, Ivek T, Kuveždić M, Novosel N, Tomić S, Korin-Hamzić B, Čulo M. Charge Transport in the Presence of Correlations and Disorder: Organic Conductors and Manganites. Materials (Basel) 2024; 17:1524. [PMID: 38612039 PMCID: PMC11013020 DOI: 10.3390/ma17071524] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/20/2024] [Revised: 03/20/2024] [Accepted: 03/21/2024] [Indexed: 04/14/2024]
Abstract
One of the most fascinating aspects of condensed matter is its ability to conduct electricity, which is particularly pronounced in conventional metals such as copper or silver. Such behavior stems from a strong tendency of valence electrons to delocalize in a periodic potential created by ions in the crystal lattice of a given material. In many advanced materials, however, this basic delocalization process of the valence electrons competes with various processes that tend to localize these very same valence electrons, thus driving the insulating behavior. The two such most important processes are the Mott localization, driven by strong correlation effects among the valence electrons, and the Anderson localization, driven by the interaction of the valence electrons with a strong disorder potential. These two localization processes are almost exclusively considered separately from both an experimental and a theoretical standpoint. Here, we offer an overview of our long-standing research on selected organic conductors and manganites, that clearly show the presence of both these localization processes. We discuss these results within existing theories of Mott-Anderson localization and argue that such behavior could be a common feature of many advanced materials.
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Affiliation(s)
- Emil Tafra
- Department of Physics, Faculty of Science, University of Zagreb, Bijenička Cesta 32, HR-10000 Zagreb, Croatia; (E.T.); (M.B.)
| | - Mario Basletić
- Department of Physics, Faculty of Science, University of Zagreb, Bijenička Cesta 32, HR-10000 Zagreb, Croatia; (E.T.); (M.B.)
| | - Tomislav Ivek
- Institut za Fiziku, Bijenička Cesta 46, HR-10000 Zagreb, Croatia; (T.I.); (N.N.); (S.T.); (B.K.-H.)
| | - Marko Kuveždić
- Department of Physics, Faculty of Science, University of Zagreb, Bijenička Cesta 32, HR-10000 Zagreb, Croatia; (E.T.); (M.B.)
| | - Nikolina Novosel
- Institut za Fiziku, Bijenička Cesta 46, HR-10000 Zagreb, Croatia; (T.I.); (N.N.); (S.T.); (B.K.-H.)
| | - Silvia Tomić
- Institut za Fiziku, Bijenička Cesta 46, HR-10000 Zagreb, Croatia; (T.I.); (N.N.); (S.T.); (B.K.-H.)
| | - Bojana Korin-Hamzić
- Institut za Fiziku, Bijenička Cesta 46, HR-10000 Zagreb, Croatia; (T.I.); (N.N.); (S.T.); (B.K.-H.)
| | - Matija Čulo
- Institut za Fiziku, Bijenička Cesta 46, HR-10000 Zagreb, Croatia; (T.I.); (N.N.); (S.T.); (B.K.-H.)
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Murase H, Arai S, Hasegawa T, Miyagawa K, Kanoda K. Spatiotemporal observation of quantum crystallization of electrons. Nat Commun 2023; 14:6011. [PMID: 37752186 PMCID: PMC10522630 DOI: 10.1038/s41467-023-41731-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2021] [Accepted: 09/12/2023] [Indexed: 09/28/2023] Open
Abstract
Liquids crystallize as they cool; however, when crystallization is avoided in some way, they supercool, maintaining their liquidity, and freezing into glass at low temperatures, as ubiquitously observed. These metastable states crystallize over time through the classical dynamics of nucleation and growth. However, it was recently found that Coulomb interacting electrons on charge-frustrated triangular lattices exhibit supercooled liquid and glass with quantum nature and they crystallize, raising fundamental issues: what features are universal to crystallization at large and specific to that of quantum systems? Here, we report our experimental challenges that address this issue through the spatiotemporal observation of electronic crystallization in an organic material. With Raman microspectroscopy, we have successfully performed real-space and real-time imaging of electronic crystallization. The results directly capture strongly temperature-dependent crystallization profiles indicating that nucleation and growth proceed at distinctive temperature-dependent rates, which is common to conventional crystallization. However, the growth rate is many orders of magnitude larger than that in the conventional case. The temperature characteristics of nucleation and growth are universal, whereas unusually fast growth kinetics features quantum crystallization where a quantum-to-classical catastrophe occurs in interacting electrons.
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Affiliation(s)
- Hideaki Murase
- Department of Applied Physics, University of Tokyo, Bunkyo-ku, Tokyo, 113-8656, Japan
| | - Shunto Arai
- Department of Applied Physics, University of Tokyo, Bunkyo-ku, Tokyo, 113-8656, Japan
- Research Center for Macromolecules and Biomaterials, National Institute for Materials Science (NIMS), Tsukuba, Ibaraki, 305-0044, Japan
| | - Tatsuo Hasegawa
- Department of Applied Physics, University of Tokyo, Bunkyo-ku, Tokyo, 113-8656, 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.
- Max Planck Institute for Solid State Research, Heisenbergstrasse 1, 70569, Stuttgart, Germany.
- Physics Institute, University of Stuttgart, Pfaffenwaldring 57, 70569, Stuttgart, Germany.
- Department of Advanced Materials Science, University of Tokyo, Kashiwanoha 5-1-5, Kashiwa, 277-8561, Japan.
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3
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Tanaka Y, Mochizuki M. Dynamical Phase Transitions in the Photodriven Charge-Ordered Dirac-Electron System. Phys Rev Lett 2022; 129:047402. [PMID: 35939024 DOI: 10.1103/physrevlett.129.047402] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/05/2022] [Revised: 05/15/2022] [Accepted: 06/29/2022] [Indexed: 06/15/2023]
Abstract
We study photoinduced phase transitions and charge dynamics in the interacting Dirac-electron system with a charge-ordered ground state theoretically by taking an organic salt α-(BEDT-TTF)_{2}I_{3}. By analyzing the extended Hubbard model for this compound using a combined method of numerical simulations based on the time-dependent Schrödinger equation and the Floquet theory, we observe successive dynamical phase transitions from the charge-ordered insulator to a gapless Dirac semimetal and, eventually, to a Chern insulator phase under irradiation with circularly polarized light. These phase transitions occur as a consequence of two major effects of circularly polarized light, i.e., closing of the charge gap through melting the charge order and opening of the topological gap by breaking the time-reversal symmetry at the Dirac points. We demonstrate that these photoinduced phenomena are governed by charge dynamics of driven correlated Dirac electrons.
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Affiliation(s)
- Yasuhiro Tanaka
- Department of Applied Physics, Waseda University, Okubo, Shinjuku-ku, Tokyo 169-8555, Japan
| | - Masahito Mochizuki
- Department of Applied Physics, Waseda University, Okubo, Shinjuku-ku, Tokyo 169-8555, Japan
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4
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Abstract
This short review article provides the reader with a summary of the history of organic conductors. To retain a neutral and objective point of view regarding the history, background, novelty, and details of each research subject within this field, a thousand references have been cited with full titles and arranged in chronological order. Among the research conducted over ~70 years, topics from the last two decades are discussed in more detail than the rest. Unlike other papers in this issue, this review will help readers to understand the origin of each topic within the field of organic conductors and how they have evolved. Due to the advancements achieved over these 70 years, the field is nearing new horizons. As history is often a reflection of the future, this review is expected to show the future directions of this research field.
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Gerasimenko YA, Vaskivskyi I, Litskevich M, Ravnik J, Vodeb J, Diego M, Kabanov V, Mihailovic D. Quantum jamming transition to a correlated electron glass in 1T-TaS 2. Nat Mater 2019; 18:1078-1083. [PMID: 31308513 DOI: 10.1038/s41563-019-0423-3] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/13/2018] [Accepted: 06/04/2019] [Indexed: 05/17/2023]
Abstract
Distinct many-body states may be created under non-equilibrium conditions through different ordering paths, even when their constituents are subjected to the same fundamental interactions. The phase-transition mechanism to such states remains poorly understood. Here, we show that controlled optical or electromagnetic perturbations can lead to an amorphous metastable state of strongly correlated electrons in a quasi-two-dimensional dichalcogenide. Scanning tunnelling microscopy reveals a hyperuniform pattern of localized charges, whereas multitip surface nanoscale conductivity measurements and tunnelling spectroscopy show an electronically gapless conducting state that is different from conventional Coulomb glasses and many-body localized systems. The state is stable up to room temperature and shows no signs of either local charge order or phase separation. The mechanism for its formation is attributed to a dynamical localization of electrons through mutual interactions. Theoretical calculations confirm the correlations between localized charges to be crucial for the state's unusual stability.
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Affiliation(s)
| | | | - Maksim Litskevich
- Department of Complex Matter, Jozef Stefan Institute, Ljubljana, Slovenia
- Laboratory for Topological Quantum Matter and Advanced Spectroscopy, Department of Physics, Princeton University, Princeton, NJ, USA
| | - Jan Ravnik
- Department of Complex Matter, Jozef Stefan Institute, Ljubljana, Slovenia
- Department of Physics, Faculty of Mathematics and Physics, University of Ljubljana, Ljubljana, Slovenia
| | - Jaka Vodeb
- Department of Complex Matter, Jozef Stefan Institute, Ljubljana, Slovenia
- Department of Physics, Faculty of Mathematics and Physics, University of Ljubljana, Ljubljana, Slovenia
| | - Michele Diego
- Department of Complex Matter, Jozef Stefan Institute, Ljubljana, Slovenia
| | - Viktor Kabanov
- Department of Complex Matter, Jozef Stefan Institute, Ljubljana, Slovenia
| | - Dragan Mihailovic
- CENN Nanocenter, Ljubljana, Slovenia.
- Department of Complex Matter, Jozef Stefan Institute, Ljubljana, Slovenia.
- Department of Physics, Faculty of Mathematics and Physics, University of Ljubljana, Ljubljana, Slovenia.
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Ikeda T, Tsunetsugu H, Yonemitsu K. Photoinduced Dynamics of Commensurate Charge Density Wave in 1T-TaS2 Based on Three-Orbital Hubbard Model. Applied Sciences 2019; 9:70. [DOI: 10.3390/app9010070] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
We study the coupled charge-lattice dynamics in the commensurate charge density wave (CDW) phase of the layered compound 1T-TaS 2 driven by an ultrashort laser pulse. For describing its electronic structure, we employ a tight-binding model of previous studies including the effects of lattice distortion associated with the CDW order. We further add on-site Coulomb interactions and reproduce an energy gap at the Fermi level within a mean-field analysis. On the basis of coupled equations of motion for electrons and the lattice distortion, we numerically study their dynamics driven by an ultrashort laser pulse. We find that the CDW order decreases and even disappears during the laser irradiation while the lattice distortion is almost frozen. We also find that the lattice motion sets in on a longer time scale and causes a further decrease in the CDW order even after the laser irradiation.
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7
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Zhu Y, Hoffman J, Rowland CE, Park H, Walko DA, Freeland JW, Ryan PJ, Schaller RD, Bhattacharya A, Wen H. Unconventional slowing down of electronic recovery in photoexcited charge-ordered La 1/3Sr 2/3FeO 3. Nat Commun 2018; 9:1799. [PMID: 29728580 DOI: 10.1038/s41467-018-04199-4] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2017] [Accepted: 04/11/2018] [Indexed: 12/03/2022] Open
Abstract
The coupling of ordered electronic phases with lattice, spin, and orbital degrees of freedom are of central interest in strongly correlated systems. Their interplay has been intensively studied from femtosecond to picosecond time scales, while their dynamics beyond nanoseconds are usually assumed to follow lattice cooling. Here, we report an unusual slowing down of the recovery of an electronic phase across a first-order phase transition. Following optical excitation, the recovery time of both transient optical reflectivity and X-ray diffraction intensity from the charge-ordered superstructure in a La1/3Sr2/3FeO3 thin film increases by orders of magnitude as the sample temperature approaches the phase transition temperature. In this regime, the recovery time becomes much longer than the lattice cooling time. The combined experimental and theoretical investigation shows that the slowing down of electronic recovery corresponds to the pseudo-critical dynamics that originates from magnetic interactions close to a weakly first-order phase transition. Unusual electronic behavior can emerge in complex oxides due to strong coupling between charge, magnetic and lattice degrees of freedom. Zhu et al. observe separation of electronic and lattice equilibration times in La1/3Sr2/3FeO3 as magnetic interactions make the recovery of charge order much slower than lattice relaxation.
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Kumagai S, Takaishi S, Iguchi H, Breedlove BK, Kaneko T, Ito H, Kuroda SI, Yamashita M. Correlation between Chemical and Physical Pressures on Charge Bistability in [Pd(en) 2Br](Suc-C n) 2·H 2O. Inorg Chem 2018; 57:12-15. [PMID: 29227105 DOI: 10.1021/acs.inorgchem.7b02566] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Hydrostatic (physical) pressure effects on the electrical resistivity of a bromido-bridged palladium compound, [Pd(en)2Br](Suc-C5)2·H2O, were studied. The charge-density-wave to Mott-Hubbard phase transition temperature (TPT) steadily increased with pressure. By a comparison of the effects of the chemical and physical pressures on TPT, it was estimated that the chemical pressure by unit alkyl chain length, i.e., the number of carbon atoms in the alkyl chains within the counterion, corresponded to ca. 1.3 kbar of the physical pressure.
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Affiliation(s)
- Shohei Kumagai
- Department of Chemistry, Graduate School of Science, Tohoku University , 6-3 Aza-Aoba, Aramaki, Aoba-ku, Sendai 980-8578, Japan
| | - Shinya Takaishi
- Department of Chemistry, Graduate School of Science, Tohoku University , 6-3 Aza-Aoba, Aramaki, Aoba-ku, Sendai 980-8578, Japan
| | - Hiroaki Iguchi
- Department of Chemistry, Graduate School of Science, Tohoku University , 6-3 Aza-Aoba, Aramaki, Aoba-ku, Sendai 980-8578, Japan
| | - Brian K Breedlove
- Department of Chemistry, Graduate School of Science, Tohoku University , 6-3 Aza-Aoba, Aramaki, Aoba-ku, Sendai 980-8578, Japan
| | - Takuya Kaneko
- Department of Applied Physics, Graduate School of Engineering, Nagoya University , Chikusa Ward, Furocho, Nagoya 464-0814, Japan
| | - Hiroshi Ito
- Department of Applied Physics, Graduate School of Engineering, Nagoya University , Chikusa Ward, Furocho, Nagoya 464-0814, Japan
| | - Shin-Ichi Kuroda
- Department of Applied Physics, Graduate School of Engineering, Nagoya University , Chikusa Ward, Furocho, Nagoya 464-0814, Japan
| | - Masahiro Yamashita
- Department of Chemistry, Graduate School of Science, Tohoku University , 6-3 Aza-Aoba, Aramaki, Aoba-ku, Sendai 980-8578, Japan.,Advanced Institute of Materials Research, Tohoku University , 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan.,School of Materials Science and Engineering, Nankai University , Tianjin 300350, China
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9
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Morimoto T, Miyamoto T, Okamoto H. Ultrafast Electron and Molecular Dynamics in Photoinduced and Electric-Field-Induced Neutral–Ionic Transitions. Crystals 2017; 7:132. [DOI: 10.3390/cryst7050132] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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10
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Yamakawa H, Miyamoto T, Morimoto T, Yada H, Kinoshita Y, Sotome M, Kida N, Yamamoto K, Iwano K, Matsumoto Y, Watanabe S, Shimoi Y, Suda M, Yamamoto HM, Mori H, Okamoto H. Novel electronic ferroelectricity in an organic charge-order insulator investigated with terahertz-pump optical-probe spectroscopy. Sci Rep 2016; 6:20571. [PMID: 26864779 PMCID: PMC4750076 DOI: 10.1038/srep20571] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2015] [Accepted: 01/06/2016] [Indexed: 11/18/2022] Open
Abstract
In electronic-type ferroelectrics, where dipole moments produced by the variations of electron configurations are aligned, the polarization is expected to be rapidly controlled by electric fields. Such a feature can be used for high-speed electric-switching and memory devices. Electronic-type ferroelectrics include charge degrees of freedom, so that they are sometimes conductive, complicating dielectric measurements. This makes difficult the exploration of electronic-type ferroelectrics and the understanding of their ferroelectric nature. Here, we show unambiguous evidence for electronic ferroelectricity in the charge-order (CO) phase of a prototypical ET-based molecular compound, α-(ET)2I3 (ET:bis(ethylenedithio)tetrathiafulvalene), using a terahertz pulse as an external electric field. Terahertz-pump second-harmonic-generation(SHG)-probe and optical-reflectivity-probe spectroscopy reveal that the ferroelectric polarization originates from intermolecular charge transfers and is inclined 27° from the horizontal CO stripe. These features are qualitatively reproduced by the density-functional-theory calculation. After sub-picosecond polarization modulation by terahertz fields, prominent oscillations appear in the reflectivity but not in the SHG-probe results, suggesting that the CO is coupled with molecular displacements, while the ferroelectricity is electronic in nature. The results presented here demonstrate that terahertz-pump optical-probe spectroscopy is a powerful tool not only for rapidly controlling polarizations, but also for clarifying the mechanisms of ferroelectricity.
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Affiliation(s)
- H Yamakawa
- Department of Advanced Materials Science, The University of Tokyo, Chiba 277-8561, Japan
| | - T Miyamoto
- Department of Advanced Materials Science, The University of Tokyo, Chiba 277-8561, Japan
| | - T Morimoto
- Department of Advanced Materials Science, The University of Tokyo, Chiba 277-8561, Japan
| | - H Yada
- Department of Advanced Materials Science, The University of Tokyo, Chiba 277-8561, Japan
| | - Y Kinoshita
- Department of Advanced Materials Science, The University of Tokyo, Chiba 277-8561, Japan
| | - M Sotome
- Department of Advanced Materials Science, The University of Tokyo, Chiba 277-8561, Japan
| | - N Kida
- Department of Advanced Materials Science, The University of Tokyo, Chiba 277-8561, Japan
| | - K Yamamoto
- Department of Applied Physics, Okayama University of Science, Okayama 700-0005, Japan
| | - K Iwano
- Institute of Materials Structure Science, Graduate University for Advanced Studies, High Energy Accelerator Research Organization (KEK), Tsukuba 305-0801, Japan
| | - Y Matsumoto
- National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba 305-8568, Japan
| | - S Watanabe
- National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba 305-8568, Japan
| | - Y Shimoi
- National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba 305-8568, Japan
| | - M Suda
- Division of Functional Molecular Systems, Research Centre of Integrative Molecular Systems (CIMoS), Institute for Molecular Science, Okazaki 444-8585, Japan
| | - H M Yamamoto
- Division of Functional Molecular Systems, Research Centre of Integrative Molecular Systems (CIMoS), Institute for Molecular Science, Okazaki 444-8585, Japan.,RIKEN, Wako 351-0198, Japan
| | - H Mori
- The Institute for Solid State Physics, The University of Tokyo, Chiba 277-8581, Japan
| | - H Okamoto
- Department of Advanced Materials Science, The University of Tokyo, Chiba 277-8561, Japan
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Kamioka H, Tsukada H, Yamaguchi R, Tateno T, Suzuki Y, Fukui Y. Time-resolved imaging and spectroscopy for the photo-induced phase transition in Ti4O7. J Photochem Photobiol A Chem 2015; 311:154-9. [DOI: 10.1016/j.jphotochem.2015.06.027] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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12
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Onda K, Yamochi H, Koshihara SY. Diverse photoinduced dynamics in an organic charge-transfer complex having strong electron-phonon interactions. Acc Chem Res 2014; 47:3494-503. [PMID: 25340327 DOI: 10.1021/ar500257b] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
CONSPECTUS: Phenomena that occur in nonequilibrium states created by photoexcitation differ qualitatively from those that occur at thermal equilibrium, and various physical theories developed for thermal equilibrium states can hardly be applied to such phenomena. Recently it has been realized that understanding phenomena in nonequilibrium states in solids is important for photoenergy usage and ultrafast computing. Consequently, much effort has been devoted to revealing such phenomena by developing various ultrafast observation techniques and theories applicable to nonequilibrium states. This Account describes our recent studies of diverse photoinduced dynamics in a strongly correlated organic solid using various ultrafast techniques. Solids in which the electronic behavior is affected by Coulomb interactions between electrons are designated as strongly correlated materials and are known to exhibit unique physical properties even at thermal equilibrium. Among them, many organic charge-transfer (CT) complexes have low dimensionality and flexibility in addition to strong correlations; thus, their physical properties change sensitively in response to changes in pressure or electric field. Photoexcitation is also expected to drastically change their physical properties and would be useful for ultrafast photoswitching devices. However, in nonequilibrium states, the complicated dynamics due to these characteristics prevents us from understanding and using these materials for photonic devices. The CT complex (EDO-TTF)2PF6 (EDO-TTF = 4,5-ethylenedioxytetrathiafulvalene) exhibits unique photoinduced dynamics due to strong electron-electron and electron-phonon interactions. We have performed detailed studies of the dynamics of this complex using transient electronic spectroscopy at the 10 and 100 fs time scales. These studies include transient vibrational spectroscopy, which is sensitive to the charges and structures of constituent molecules, and transient electron diffraction, which provides direct information on the crystal structure. Photoexcitation of the charge-ordered low-temperature phase of (EDO-TTF)2PF6 creates a new photoinduced phase over 40 fs via the Franck-Condon state, in which electrons and vibrations are coherently and strongly coupled. This new photoinduced phase is assigned to an insulator-like state in which the charge order differs from that of the initial state. In the photoinduced phase, translations of component molecules proceed before the rearrangements of intramolecular conformations. Subsequently, the charge order and structure gradually approach those of the high-temperature phase over 100 ps. This unusual two-step photoinduced phase transition presumably originates from steric effects due to the bent EDO-TTF as well as strong electron-lattice interactions.
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Affiliation(s)
- Ken Onda
- Interactive
Research Center of Science, Tokyo Institute of Technology, Nagatsuta, Midori-ku, Yokohama, Kanagawa 226-8502, Japan
- PRESTO, Japan Science and Technology Agency (JST), 4-1-8 Honcho, Kawaguchi, Saitama 332-0012, Japan
| | - Hideki Yamochi
- Research
Center for Low Temperature and Materials Sciences, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan
| | - Shin-ya Koshihara
- Department
of Chemistry and Materials Science, Tokyo Institute of Technology, O-okayama, Meguro-ku, Tokyo 152-8551, Japan
- CREST, Japan Science and Technology Agency (JST),
O-okayama, Meguro-ku, Tokyo 152-8551, Japan
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Abstract
Electronic ferroelectricity in molecular organic crystals is reviewed from a theoretical perspective. In particular, we focus on the charge-driven-type electronic ferroelectricity where electronic charge order without inversion symmetry induces a spontaneous electric polarization in quarter-filling systems. Two necessary conditions to realize this type of ferroelectricity are the dimer-type lattice structure and alternate electronic charge alignments. Some prototypical organic compounds are introduced. In particular, κ-type BEDT-TTF organic salts, which are termed the dimer-Mott insulating systems, are focused on. Recent developments in the theoretical researches for dielectric and magnetodielectric properties, a collective dipole excitation and a possibility of superconductivity induced by polar charge fluctuation are reviewed. Some perspectives are presented.
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Affiliation(s)
- Sumio Ishihara
- Department of Physics, Tohoku University, Sendai 980-8578, Japan CREST, Sendai 980-8578, Japan
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14
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Ishikawa T, Sagae Y, Naitoh Y, Kawakami Y, Itoh H, Yamamoto K, Yakushi K, Kishida H, Sasaki T, Ishihara S, Tanaka Y, Yonemitsu K, Iwai S. Optical freezing of charge motion in an organic conductor. Nat Commun 2014; 5. [DOI: 10.1038/ncomms6528] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2014] [Accepted: 10/09/2014] [Indexed: 11/08/2022] Open
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15
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Takubo N, Tajima N, Yamamoto HM, Kato R. Nonlinear photocurrent with a threshold of excitation density induced by the long-range electron-electron interaction in the charge-ordered molecular conductor (BEDT-TTF)3(ClO4)2. J Phys Condens Matter 2014; 26:055603. [PMID: 24444590 DOI: 10.1088/0953-8984/26/2/055603] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
We investigated a photoexcited state in the molecular conductor (BEDT-TTF)3(ClO4)2 (BEDT-TTF = bis(ethylenedithio)tetrathiafulvalene) with charge localization due to the electron-electron Coulomb interaction. Photocurrent induced by intramolecular excitation was observed in a charge-ordered insulating state. As a result, nonlinear photocurrent with a threshold of excitation light density was experimentally obtained. The threshold decreased as the temperature increased. This nonlinear photocurrent indicates a transition from an excitonic state to a free excited electronic state. The excitonic state below the threshold is formed by the long-range electron-electron Coulomb interaction. In the free excited electronic state above the threshold, high-density photoexcitation induces Coulomb screening, which results in exciton dissociation and a free electronic state.
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Affiliation(s)
- Naoko Takubo
- RIKEN, Hirosawa 2-1, Wako-shi, Saitama 351-0198, Japan
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16
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Tanaka Y, Yonemitsu K. Charge order and possible bias-induced metastable state in the organic conductor β-(meso-DMBEDT-TTF)2PF6: effects of structural distortion. J Phys Condens Matter 2013; 25:465603. [PMID: 24158705 DOI: 10.1088/0953-8984/25/46/465603] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
We theoretically investigate charge order and nonlinear conduction in the quasi-two-dimensional organic conductor β-(meso-DMBEDT-TTF)2PF6 (DMBEDT-TTF=dimethylbis(ethylenedithio)tetrathiafulvalene). Within the Hartree-Fock approximation, we study the effects of structural distortion on the experimentally observed checkerboard charge order and its bias-induced melting by using an extended Hubbard model with Peierls- and Holstein-types of electron-lattice interactions. The structural distortion is important in realizing the charge order. The current-voltage characteristics obtained by a nonequilibrium Green's function method indicate that a charge-ordered insulating state changes into a conductive state. Although the charge order and lattice distortions are largely suppressed at a threshold voltage, they remain finite even in the conductive state. We discuss the relevance of the results to experimental observations, especially to a possible bias-induced metastable state.
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Affiliation(s)
- Y Tanaka
- Department of Physics, Chuo University, Bunkyo-ku, Tokyo 112-8551, Japan. JST, CREST, Chiyoda-ku, Tokyo 102-0076, Japan
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Ito A, Nakamura Y, Nakamura A, Kishida H. Measurement of the nonlinear conducting states of α-(BEDT-TTF)2I3 using electronic Raman scattering. Phys Rev Lett 2013; 111:197801. [PMID: 24266489 DOI: 10.1103/physrevlett.111.197801] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/29/2011] [Revised: 04/22/2013] [Indexed: 06/02/2023]
Abstract
Nonlinear conducting states in a strongly correlated organic electronic system α-(BEDT-TTF)2I3 [BEDT-TTF=bis(ethylenedithio)-tetrathiafulvalene] are studied by Raman spectroscopy. Wide-range Raman spectra of nonlinear conducing states provide direct information about conducting properties through the electronic Raman process. A comparison between the behaviors of the electronic modes of BEDT-TTF layers and the vibrational mode of I3 molecules reveals the formation of nonequilibrium states in which only the electronic parts show the change of states. We obtained a spatial map of the conducting regions of the nonlinear conducting states by utilizing the electronic Raman intensity as a measure of the highly conducting states. A spatially inhomogeneous formation of nonlinear conducting states was observed.
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Affiliation(s)
- Atsuya Ito
- Department of Applied Physics, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603, Japan
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Takubo N, Tajima N, Yamamoto HM, Cui H, Kato R. Lattice distortion stabilizes the photoinduced metallic phase in the charge-ordered organic salts (BEDT-TTF)3X2 (X=ReO4, ClO4). Phys Rev Lett 2013; 110:227401. [PMID: 23767745 DOI: 10.1103/physrevlett.110.227401] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/17/2012] [Indexed: 06/02/2023]
Abstract
Photoinduced effects caused by intramolecular excitation were investigated by simultaneous optical and transport measurement in two charge-ordered organic salts, (BEDT-TTF)3X2 (X=ReO4, ClO4) [BEDT-TTF=bis(ethylenedithio)tetrathiafulvalene]. Although the two salts have the same molecular (average) charge and arrangement, they showed different photoinduced effects. A photoinduced insulator-to-metal phase transition with a metastable charge order-melting state was observed in the ReO4 salt where the charge ordered state is associated with the lattice distortion. On the other hand, no photoinduced insulator-to-metal phase transition was noted in the ClO4 salt where the charge ordered state is not accompanied by the lattice distortion. This comparative study suggested that the lattice distortion plays a key role in the stabilization of the photoinduced phase.
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Affiliation(s)
- Naoko Takubo
- RIKEN, Hirosawa 2-1, Wako-shi, Saitama 351-0198, Japan
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Itoh K, Itoh H, Naka M, Saito S, Hosako I, Yoneyama N, Ishihara S, Sasaki T, Iwai S. Collective excitation of an electric dipole on a molecular dimer in an organic dimer-Mott insulator. Phys Rev Lett 2013; 110:106401. [PMID: 23521274 DOI: 10.1103/physrevlett.110.106401] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/06/2012] [Revised: 12/21/2012] [Indexed: 06/01/2023]
Abstract
The terahertz response in 10-100 cm(-1) was investigated in an organic dimer-Mott (DM) insulator κ-(ET)(2)Cu(2)(CN)(3) that exhibits a relaxorlike dielectric anomaly. An ~30 cm(-1) band in the optical conductivity was attributable to collective excitation of the fluctuating intradimer electric dipoles that are formed by an electron correlation. We succeeded in observing photoinduced enhancement of this ~30 cm(-1) band, reflecting the growth of the electric dipole cluster in the DM phase. Such optical responses in κ-(ET)(2)Cu(2)(CN)(3) reflect an instability near the boundary between the DM-ferroelectric charge ordered phases.
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Affiliation(s)
- K Itoh
- Department of Physics, Tohoku University, Sendai 980-8578, Japan
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Iwai S, Kawakami Y, Ishikawa T, Sakurai Y, Itoh H, Yamamoto K, Sasaki T. Coherent Electron Dynamics in 10 fs Time Scale in Organic Charge Ordered and Dimer-Mott Insulators. EPJ Web of Conferences 2013. [DOI: 10.1051/epjconf/20134103019] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Yakushi K. Infrared and Raman Studies of Charge Ordering in Organic Conductors, BEDT-TTF Salts with Quarter-Filled Bands. Crystals 2012; 2:1291-346. [DOI: 10.3390/cryst2031291] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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22
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Ishikawa T, Onda K, Koshihara S. Photoinduced Phase Transition in Strongly Electron-Lattice and Electron–Electron Correlated Molecular Crystals. Crystals 2012; 2:1067-83. [DOI: 10.3390/cryst2031067] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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Iwai S. Photoinduced Phase Transitions in α-, θ-, and κ-type ET Salts: Ultrafast Melting of the Electronic Ordering. Crystals 2012; 2:590-617. [DOI: 10.3390/cryst2020590] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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Yonemitsu K. Theory of Photoinduced Phase Transitions in Molecular Conductors: Interplay Between Correlated Electrons, Lattice Phonons and Molecular Vibrations. Crystals 2012; 2:56-77. [DOI: 10.3390/cryst2010056] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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Kawakami Y, Fukatsu T, Sakurai Y, Unno H, Itoh H, Iwai S, Sasaki T, Yamamoto K, Yakushi K, Yonemitsu K. Early-stage dynamics of light-matter interaction leading to the insulator-to-metal transition in a charge ordered organic crystal. Phys Rev Lett 2010; 105:246402. [PMID: 21231538 DOI: 10.1103/physrevlett.105.246402] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/23/2010] [Indexed: 05/30/2023]
Abstract
Ultrafast dynamics of the light-matter interaction in a charge-ordered molecular insulator α-(BEDT-TTF)2I3 were studied by pump-probe spectroscopy using few-optical-cycle infrared pulses (pulse width 12 fs). Coherent oscillation of the correlated electrons and subsequent Fano destructive interference with intramolecular vibration were observed in time domain; the results indicated a crucial role for electron-electron interplay in the light-matter interaction leading to the photoinduced insulator-to-metal transition. The qualitative features of this correlated electron motion were reproduced by calculations based on exact many-electron-phonon wave functions.
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Affiliation(s)
- Y Kawakami
- Department of Physics, Tohoku University, Sendai 980-8578, Japan
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26
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Kawakami Y, Iwai S, Fukatsu T, Miura M, Yoneyama N, Sasaki T, Kobayashi N. Optical modulation of effective on-site coulomb energy for the Mott transition in an organic dimer insulator. Phys Rev Lett 2009; 103:066403. [PMID: 19792588 DOI: 10.1103/physrevlett.103.066403] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/26/2009] [Indexed: 05/28/2023]
Abstract
We report an optical modulation of the effective on-site Coulomb energy U on a dimer (U_{dimer}) for achieving the Mott insulator-to-metal transition in kappa-(BEDT-TTF)_{2}Cu[N(CN)_{2}]Br, as investigated by pump-probe spectroscopy. A reduction of U_{dimer} is optically induced by molecule displacement in the dimer under intradimer excitation. The mechanism of this metallization differs greatly from the photodoping-type mechanism reported previously. In contrast, a faster transition via the photodoping mechanism is detected for interdimer excitation. A metallic-domain-wall oscillation originating from the modulation of U_{dimer} was also observed near the critical end point of the Mott transition line.
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Affiliation(s)
- Y Kawakami
- Department of Physics, Tohoku University, Sendai 980-8578, Japan
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Yamochi H, Koshihara SY. Organic metal (EDO-TTF) 2PF 6 with multi-instability. Sci Technol Adv Mater 2009; 10:024305. [PMID: 27877278 PMCID: PMC5090435 DOI: 10.1088/1468-6996/10/2/024305] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/01/2008] [Revised: 07/06/2009] [Accepted: 01/14/2009] [Indexed: 06/06/2023]
Abstract
The multi-instability of the electronic structure of (EDO-TTF)2PF6, where EDO-TTF means ethylene-dioxytetrathiafulvalene, is reviewed. This complex showed the metal-insulator transition at 280 K associated with distinct molecular deformations. The mechanism is interpreted as the cooperation of Peierls transition, charge ordering, and the order-disorder transition of the countercomponent. The charge ordering pattern in the low-temperature phase is of the novel [0, 0, 1, 1] type. The sensitivity of the electronic state to external perturbations is demonstrated applying not only static but also instantaneous stimuli. In the latter case, the photo-induced phase transition is ultrafast and highly efficient. One photon causes the transition of several hundreds of donor molecules in the low-temperature phase to relax into a highly conducting metastable state within about 1.5 ps. In the early stage of the transient state, the charge ordering of the [1, 0, 1, 0] type occurs. As for the chemical modifications of this material, the partial deuteration of this complex increases the metal-insulator transition temperature. The introduction of a methyl group greatly modulates the electronic structure of the complex, i.e. (methyl-EDO-TTF)2X (X=BF4, ClO4) shows a two-dimensional electronic structure. The working hypotheses for developing the systems with multi-instability are described.
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Affiliation(s)
- Hideki Yamochi
- Research Center for Low Temperature and Materials Sciences, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan
- Nonequilibrium Dynamics Project, ERATO/JST, Tsukuba, Ibaraki 305-0801, Japan
| | - Shin-ya Koshihara
- Nonequilibrium Dynamics Project, ERATO/JST, Tsukuba, Ibaraki 305-0801, Japan
- Department of Materials Science, Tokyo Institute of Technology, Meguro-ku, Tokyo 152-8551, Japan
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Onda K, Ogihara S, Yonemitsu K, Maeshima N, Ishikawa T, Okimoto Y, Shao X, Nakano Y, Yamochi H, Saito G, Koshihara SY. Photoinduced change in the charge order pattern in the quarter-filled organic conductor (EDO-TTF)2PF6 with a strong electron-phonon interaction. Phys Rev Lett 2008; 101:067403. [PMID: 18764502 DOI: 10.1103/physrevlett.101.067403] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/24/2008] [Indexed: 05/26/2023]
Abstract
The quasistable state in the photoinduced phase transition for the quasi-one-dimensional quarter-filled organic conductor (EDO-TTF)2PF6 has been examined by ultrafast reflective measurements and time-dependent model calculations incorporating both electron-electron and electron-phonon interactions. The transient optical conductivity spectrum over a wide probe photon-energy range revealed that photoexcitation induced a new type of charge-disproportionate state. Additionally, coherent and incoherent oscillations dependent on probe photon energies were found, as predicted by the calculation.
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Affiliation(s)
- Ken Onda
- Nonequilibrium Dynamics Project, ERATO/JST, Tsukuba, Ibaraki 305-0801, Japan
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Hotta C, Pollmann F. Dimensional tuning of electronic states under strong and frustrated interactions. Phys Rev Lett 2008; 100:186404. [PMID: 18518399 DOI: 10.1103/physrevlett.100.186404] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/18/2007] [Indexed: 05/26/2023]
Abstract
We study a model of strongly interacting spinless fermions on an anisotropic triangular lattice. At half-filling and the limit of strong repulsive nearest-neighbor interactions, the fermions align in stripes and form an insulating state. When a particle is doped, it either follows a one-dimensional free motion along the stripes or fractionalizes perpendicular to the stripes. The two propagations yield a dimensional tuning of the electronic state. We study the stability of this phase and derive an effective model to describe the low-energy excitations. Spectral functions are presented which can be used to experimentally detect signatures of the charge excitations.
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Affiliation(s)
- Chisa Hotta
- Department of Physics, Faculty of Science, Kyoto Sangyo University, Kyoto 603-8555, Japan
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Tokumoto T, Brooks JS, Oshima Y, Choi ES, Brunel LC, Akutsu H, Kaihatsu T, Yamada J, van Tol J. Antiferromagnetic d-electron exchange via a spin-singlet pi-electron ground state in an organic conductor. Phys Rev Lett 2008; 100:147602. [PMID: 18518072 DOI: 10.1103/physrevlett.100.147602] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/28/2007] [Indexed: 05/26/2023]
Abstract
Electron spin resonance reveals the spin behavior of conduction (pi) and localized (d) electrons in beta-(BDA-TTP)2MCl4 (M=Fe, Ga). Both the Ga3+(S=0) and Fe3+(S=5/2) compounds exhibit a metal-insulator transition at 113 K with the simultaneous formation of a spin-singlet ground state in the pi electron system of the donor molecules. The behavior is consistent with charge ordering in beta-(BDA-TTP)2MCl4 at the metal-insulator transition. At 5 K, the Fe3+ compound orders antiferromagnetically, even though the pi electrons, which normally would facilitate magnetic exchange, are localized nonmagnetic singlets.
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Affiliation(s)
- T Tokumoto
- National High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida 32310, USA
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