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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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Itou T, Watanabe E, Maegawa S, Tajima A, Tajima N, Kubo K, Kato R, Kanoda K. Slow dynamics of electrons at a metal-Mott insulator boundary in an organic system with disorder. SCIENCE ADVANCES 2017; 3:e1601594. [PMID: 28819640 PMCID: PMC5553821 DOI: 10.1126/sciadv.1601594] [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: 07/12/2016] [Accepted: 07/06/2017] [Indexed: 06/07/2023]
Abstract
The Mott transition-a metal-insulator transition caused by repulsive Coulomb interactions between electrons-is a central issue in condensed matter physics because it is the mother earth of various attractive phenomena. Outstanding examples are high-Tc (critical temperature) cuprates and manganites exhibiting colossal magnetoresistance. Furthermore, spin liquid states, which are quantum-fluctuation-driven disordered ground states in antiferromagnets, have recently been found in magnetic systems very near the Mott transition. To date, intensive studies on the Mott transition have been conducted and appear to have established a nearly complete framework for understanding the Mott transition. We found an unknown type of Mott transition in an organic spin liquid material with a slightly disordered lattice. Around the Mott transition region of this material under pressure, nuclear magnetic resonance experiments capture the emergence of slow electronic fluctuations of the order of kilohertz or lower, which is not expected in the conventional Mott transition that appears as a clear first-order transition at low temperatures. We suggest that they are due to the unconventional metal-insulator fluctuations emerging around the disordered Mott transition in analogy to the slowly fluctuating spin phase, or Griffiths phase, realized in Ising spin systems with disordered lattices.
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Affiliation(s)
- Tetsuaki Itou
- Department of Applied Physics, Tokyo University of Science, Katsushika-ku, Tokyo 125-8585, Japan
- Department of Applied Physics and Quantum-Phase Electronics Center (QPEC), University of Tokyo, Bunkyo-ku, Tokyo 113-8656, Japan
| | - Eri Watanabe
- Graduate School of Human and Environmental Studies, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan
| | - Satoru Maegawa
- Graduate School of Human and Environmental Studies, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan
| | - Akiko Tajima
- Condensed Molecular Materials Laboratory, RIKEN, Wako-shi, Saitama 351-0198, Japan
| | - Naoya Tajima
- Condensed Molecular Materials Laboratory, RIKEN, Wako-shi, Saitama 351-0198, Japan
- Department of Physics, Toho University, Funabashi-shi, Chiba 274-8510, Japan
| | - Kazuya Kubo
- Condensed Molecular Materials Laboratory, RIKEN, Wako-shi, Saitama 351-0198, Japan
- Research Institute for Electronic Science, Hokkaido University, Kita-ku, Sapporo 001-0020, Japan
| | - Reizo Kato
- Condensed Molecular Materials Laboratory, RIKEN, Wako-shi, Saitama 351-0198, Japan
| | - Kazushi Kanoda
- Department of Applied Physics, University of Tokyo, Bunkyo-ku, Tokyo 113-8656, Japan
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Sato Y, Kawasugi Y, Suda M, Yamamoto HM, Kato R. Critical Behavior in Doping-Driven Metal-Insulator Transition on Single-Crystalline Organic Mott-FET. NANO LETTERS 2017; 17:708-714. [PMID: 28038313 DOI: 10.1021/acs.nanolett.6b03817] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
We present the carrier transport properties in the vicinity of a doping-driven Mott transition observed at a field-effect transistor (FET) channel using a single crystal of the typical two-dimensional organic Mott insulator κ-(BEDT-TTF)2CuN(CN)2Cl (κ-Cl). The FET shows a continuous metal-insulator transition (MIT) as electrostatic doping proceeds. The phase transition appears to involve two-step crossovers, one in Hall measurement and the other in conductivity measurement. The crossover in conductivity occurs around the conductance quantum e2/h, and hence is not associated with "bad metal" behavior, which is in stark contrast to the MIT in half-filled organic Mott insulators or that in doped inorganic Mott insulators. Through in-depth scaling analysis of the conductivity, it is found that the above carrier transport properties in the vicinity of the MIT can be described by a high-temperature Mott quantum critical crossover, which is theoretically argued to be a ubiquitous feature of various types of Mott transitions.
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Affiliation(s)
| | | | - Masayuki Suda
- RIKEN, Hirosawa, Wako, Saitama 351-0198, Japan
- Research Center for Integrative Molecular System (CIMoS), Institute for Molecular Science , 38 Nishigo-naka, Myodaiji, Okazaki 444-8585, Japan
| | - Hiroshi M Yamamoto
- RIKEN, Hirosawa, Wako, Saitama 351-0198, Japan
- Research Center for Integrative Molecular System (CIMoS), Institute for Molecular Science , 38 Nishigo-naka, Myodaiji, Okazaki 444-8585, Japan
| | - Reizo Kato
- RIKEN, Hirosawa, Wako, Saitama 351-0198, Japan
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Gati E, Garst M, Manna RS, Tutsch U, Wolf B, Bartosch L, Schubert H, Sasaki T, Schlueter JA, Lang M. Breakdown of Hooke's law of elasticity at the Mott critical endpoint in an organic conductor. SCIENCE ADVANCES 2016; 2:e1601646. [PMID: 27957540 PMCID: PMC5142797 DOI: 10.1126/sciadv.1601646] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/18/2016] [Accepted: 11/03/2016] [Indexed: 05/27/2023]
Abstract
The Mott metal-insulator transition, a paradigm of strong electron-electron correlations, has been considered as a source of intriguing phenomena. Despite its importance for a wide range of materials, fundamental aspects of the transition, such as its universal properties, are still under debate. We report detailed measurements of relative length changes ΔL/L as a function of continuously controlled helium-gas pressure P for the organic conductor κ-(BEDT-TTF)2Cu[N(CN)2]Cl across the pressure-induced Mott transition. We observe strongly nonlinear variations of ΔL/L with pressure around the Mott critical endpoint, highlighting a breakdown of Hooke's law of elasticity. We assign these nonlinear strain-stress relations to an intimate, nonperturbative coupling of the critical electronic system to the lattice degrees of freedom. Our results are fully consistent with mean-field criticality, predicted for electrons in a compressible lattice with finite shear moduli. We argue that the Mott transition for all systems that are amenable to pressure tuning shows the universal properties of an isostructural solid-solid transition.
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Affiliation(s)
- Elena Gati
- Physikalisches Institut, Goethe-Universität Frankfurt, Max-von-Laue-Straße 1, 60438 Frankfurt am Main, Germany
| | - Markus Garst
- Institut für Theoretische Physik, Universität zu Köln, Zülpicher Straße 77, 50937 Köln, Germany
- Institut für Theoretische Physik, Technische Universität Dresden, Zellescher Weg 17, 01062 Dresden, Germany
| | - Rudra S. Manna
- Physikalisches Institut, Goethe-Universität Frankfurt, Max-von-Laue-Straße 1, 60438 Frankfurt am Main, Germany
| | - Ulrich Tutsch
- Physikalisches Institut, Goethe-Universität Frankfurt, Max-von-Laue-Straße 1, 60438 Frankfurt am Main, Germany
| | - Bernd Wolf
- Physikalisches Institut, Goethe-Universität Frankfurt, Max-von-Laue-Straße 1, 60438 Frankfurt am Main, Germany
| | - Lorenz Bartosch
- Institut für Theoretische Physik, Goethe-Universität Frankfurt, Max-von-Laue-Straße 1, 60438 Frankfurt am Main, Germany
| | - Harald Schubert
- Physikalisches Institut, Goethe-Universität Frankfurt, Max-von-Laue-Straße 1, 60438 Frankfurt am Main, Germany
| | - Takahiko Sasaki
- Institute for Materials Research, Tohoku University, Katahira 2-1-1, Sendai 980-8577, Japan
| | - John A. Schlueter
- Division of Materials Research, National Science Foundation, Arlington, VA 22230, USA
- Materials Science Division, Argonne National Laboratory, Argonne, IL 60439, USA
| | - Michael Lang
- Physikalisches Institut, Goethe-Universität Frankfurt, Max-von-Laue-Straße 1, 60438 Frankfurt am Main, Germany
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Lenz B, Manmana SR, Pruschke T, Assaad FF, Raczkowski M. Mott Quantum Criticality in the Anisotropic 2D Hubbard Model. PHYSICAL REVIEW LETTERS 2016; 116:086403. [PMID: 26967431 DOI: 10.1103/physrevlett.116.086403] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/03/2015] [Indexed: 06/05/2023]
Abstract
We present evidence for Mott quantum criticality in an anisotropic two-dimensional system of coupled Hubbard chains at half-filling. In this scenario emerging from variational cluster approximation and cluster dynamical mean-field theory, the interchain hopping t_{⊥} acts as a control parameter driving the second-order critical end point T_{c} of the metal-insulator transition down to zero at t_{⊥}^{c}/t≃0.2. Below t_{⊥}^{c}, the volume of the hole and electron Fermi pockets of a compensated metal vanishes continuously at the Mott transition. Above t_{⊥}^{c}, the volume reduction of the pockets is cut off by a first-order transition. We discuss the relevance of our findings to a putative quantum critical point in layered organic conductors, whose location remains elusive so far.
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Affiliation(s)
- Benjamin Lenz
- Institute for Theoretical Physics, University of Göttingen, Friedrich-Hund-Platz 1, D-37077 Göttingen, Germany
| | - Salvatore R Manmana
- Institute for Theoretical Physics, University of Göttingen, Friedrich-Hund-Platz 1, D-37077 Göttingen, Germany
| | - Thomas Pruschke
- Institute for Theoretical Physics, University of Göttingen, Friedrich-Hund-Platz 1, D-37077 Göttingen, Germany
| | - Fakher F Assaad
- Institute for Theoretical Physics and Astrophysics, University of Würzburg, Am Hubland, D-97074 Würzburg, Germany
| | - Marcin Raczkowski
- Institute for Theoretical Physics and Astrophysics, University of Würzburg, Am Hubland, D-97074 Würzburg, Germany
- Department of Physics and Arnold Sommerfeld Center for Theoretical Physics, Ludwig-Maximilians-Universität München, D-80333 München, Germany
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Diehl S, Methfessel T, Tutsch U, Müller J, Lang M, Huth M, Jourdan M, Elmers HJ. Disorder-induced gap in the normal density of states of the organic superconductor κ-(BEDT-TTF)2Cu[N(CN)2]Br. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2015; 27:265601. [PMID: 26076168 DOI: 10.1088/0953-8984/27/26/265601] [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
The local density of states (DOS) of the organic superconductor κ-(BEDT-TTF)2Cu[N(CN)2]Br, measured by scanning tunneling spectroscopy on in situ cleaved surfaces, reveals a logarithmic suppression near the Fermi edge persisting above the critical temperature T(c). The experimentally observed suppression of the DOS is in excellent agreement with a soft Hubbard gap as predicted by the Anderson-Hubbard model for systems with disorder. The electronic disorder also explains the diminished coherence peaks of the quasi-particle DOS below T(c).
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Affiliation(s)
- Sandra Diehl
- Graduate School Materials Science In Mainz, Staudingerweg 9, 55128 Mainz, Germany. Institut für Physik, Johannes Gutenberg-Universität Mainz, Staudingerweg 7, 55128 Mainz, Germany
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Hartmann B, Zielke D, Polzin J, Sasaki T, Müller J. Critical slowing down of the charge carrier dynamics at the Mott metal-insulator transition. PHYSICAL REVIEW LETTERS 2015; 114:216403. [PMID: 26066449 DOI: 10.1103/physrevlett.114.216403] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/12/2015] [Indexed: 06/04/2023]
Abstract
We report on the dramatic slowing down of the charge carrier dynamics in a quasi-two-dimensional organic conductor, which can be reversibly tuned through the Mott metal-insulator transition (MIT). At the finite-temperature critical end point, we observe a divergent increase of the resistance fluctuations accompanied by a drastic shift of spectral weight to low frequencies, demonstrating the critical slowing down of the order parameter (doublon density) fluctuations. The slow dynamics is accompanied by non-Gaussian fluctuations, indicative of correlated charge carrier dynamics. A possible explanation is a glassy freezing of the electronic system as a precursor of the Mott MIT.
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Affiliation(s)
- Benedikt Hartmann
- Institute of Physics and SFB/TR 49, Goethe-University Frankfurt, 60438 Frankfurt (M), Germany
| | - David Zielke
- Institute of Physics and SFB/TR 49, Goethe-University Frankfurt, 60438 Frankfurt (M), Germany
| | - Jana Polzin
- Institute of Physics and SFB/TR 49, Goethe-University Frankfurt, 60438 Frankfurt (M), Germany
| | - Takahiko Sasaki
- Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
| | - Jens Müller
- Institute of Physics and SFB/TR 49, Goethe-University Frankfurt, 60438 Frankfurt (M), Germany
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