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Huang Y, Wolowiec C, Zhu T, Hu Y, An L, Li Z, Grossman JC, Schuller IK, Ren S. Emerging Magnetic Interactions in van der Waals Heterostructures. NANO LETTERS 2020; 20:7852-7859. [PMID: 33054240 DOI: 10.1021/acs.nanolett.0c02175] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Vertical van der Waals (vdWs) heterostructures based on layered materials are attracting interest as a new class of quantum materials, where interfacial charge-transfer coupling can give rise to fascinating strongly correlated phenomena. Transition metal chalcogenides are a particularly exciting material family, including ferromagnetic semiconductors, multiferroics, and superconductors. Here, we report the growth of an organic-inorganic heterostructure by intercalating molecular electron donating bis(ethylenedithio)tetrathiafulvalene into (Li,Fe)OHFeSe, a layered material in which the superconducting ground state results from the intercalation of hydroxide layer. Molecular intercalation in this heterostructure induces a transformation from a paramagnetic to spin-glass-like state that is sensitive to the stoichiometry of molecular donor and an applied magnetic field. Besides, electron-donating molecules reduce the electrical resistivity in the heterostructure and modify its response to laser illumination. This hybrid heterostructure provides a promising platform to study emerging magnetic and electronic behaviors in strongly correlated layered materials.
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Affiliation(s)
- Yulong Huang
- Department of Mechanical and Aerospace Engineering, University at Buffalo, The State University of New York, Buffalo, New York 14260, United States
| | - Christian Wolowiec
- Department of Physics and Center for Advanced Nanoscience, University of California San Diego, La Jolla, California 92093, United States
| | - Taishan Zhu
- Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Yong Hu
- Department of Mechanical and Aerospace Engineering, University at Buffalo, The State University of New York, Buffalo, New York 14260, United States
| | - Lu An
- Department of Mechanical and Aerospace Engineering, University at Buffalo, The State University of New York, Buffalo, New York 14260, United States
| | - Zheng Li
- Department of Mechanical and Aerospace Engineering, University at Buffalo, The State University of New York, Buffalo, New York 14260, United States
| | - Jeffrey C Grossman
- Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Ivan K Schuller
- Department of Physics and Center for Advanced Nanoscience, University of California San Diego, La Jolla, California 92093, United States
| | - Shenqiang Ren
- Department of Mechanical and Aerospace Engineering, University at Buffalo, The State University of New York, Buffalo, New York 14260, United States
- Department of Chemistry, University at Buffalo, The State University of New York, Buffalo, New York 14260, United States
- Research and Education in Energy, Environment, and Water (RENEW) Institute, University at Buffalo, The State University of New York, Buffalo, New York 14260, United States
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Dong X, Hu Y, Ren S, Zhang P. Spatially Resolved Investigation of Mixed Valence and Insulator-to-Metal Transition in an Organic Salt. J Phys Chem Lett 2020; 11:8352-8357. [PMID: 32914983 DOI: 10.1021/acs.jpclett.0c02303] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Using scanning tunneling microscopy/spectroscopy (STM/STS), we investigate the evolution of electronic structures across the boundaries of 7,7,8,8-tetracyanoquinodimethane (TCNQ) and K-TCNQ assemblies on a weakly interacting substrate. Despite the semiconducting/insulating nature of TCNQ (TCNQ0) and K-TCNQ (TCNQ-1), a continuum metallic-like density of states extending deep (∼1.5 nm) into the TCNQ assembly is observed near the domain boundary. We attribute the formation of these states to the abrupt change of molecular valence, which perturbs the electrostatics of the junction and creates local electric fields as evidenced by the band bending near the domain boundary. To the best of our knowledge, this study provides the first microscopic understanding of the crucial physics occurring near domain boundaries of mixed valence in K-TCNQ, or broadly speaking charge-transfer complexes, which highlights these boundaries as potential "weak" points to initiate the electric field-induced insulator-to-metal transition.
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Affiliation(s)
- Xi Dong
- Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan 48824, United States
| | - Yong Hu
- Department of Mechanical and Aerospace Engineering, Research and Education in Energy Environment & Water Institute, University at Buffalo, The State University of New York, Buffalo, New York 14260, United States
| | - Shenqiang Ren
- Department of Mechanical and Aerospace Engineering, Research and Education in Energy Environment & Water Institute, University at Buffalo, The State University of New York, Buffalo, New York 14260, United States
- Department of Chemistry, University of Buffalo, The State University of New York, Buffalo, New York 14260, United States
| | - Pengpeng Zhang
- Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan 48824, United States
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Kawasugi Y, Seki K, Tajima S, Pu J, Takenobu T, Yunoki S, Yamamoto HM, Kato R. Two-dimensional ground-state mapping of a Mott-Hubbard system in a flexible field-effect device. SCIENCE ADVANCES 2019; 5:eaav7282. [PMID: 31093527 PMCID: PMC6510553 DOI: 10.1126/sciadv.aav7282] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/14/2018] [Accepted: 03/27/2019] [Indexed: 06/09/2023]
Abstract
A Mott insulator sometimes induces unconventional superconductivity in its neighbors when doped and/or pressurized. Because the phase diagram should be strongly related to the microscopic mechanism of the superconductivity, it is important to obtain the global phase diagram surrounding the Mott insulating state. However, the parameter available for controlling the ground state of most Mott insulating materials is one-dimensional owing to technical limitations. Here, we present a two-dimensional ground-state mapping for a Mott insulator using an organic field-effect device by simultaneously tuning the bandwidth and bandfilling. The observed phase diagram showed many unexpected features such as an abrupt first-order superconducting transition under electron doping, a recurrent insulating phase in the heavily electron-doped region, and a nearly constant superconducting transition temperature in a wide parameter range. These results are expected to contribute toward elucidating one of the standard solutions for the Mott-Hubbard model.
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Affiliation(s)
| | - Kazuhiro Seki
- RIKEN, Wako, Saitama 351-0198, Japan
- SISSA–International School for Advanced Studies, Via Bonomea 265, 34136 Trieste, Italy
- RIKEN Center for Computational Science (R-CCS), Kobe, Hyogo 650-0047, Japan
| | - Satoshi Tajima
- Department of Physics, Toho University, Funabashi, Chiba 274-8510, Japan
| | - Jiang Pu
- Department of Applied Physics, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603, Japan
| | - Taishi Takenobu
- Department of Applied Physics, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603, Japan
| | - Seiji Yunoki
- RIKEN, Wako, Saitama 351-0198, Japan
- RIKEN Center for Computational Science (R-CCS), Kobe, Hyogo 650-0047, Japan
- RIKEN Center for Emergent Matter Science (CEMS), Wako, Saitama 351-0198, Japan
| | - Hiroshi M. Yamamoto
- RIKEN, Wako, Saitama 351-0198, Japan
- Research Center of Integrative Molecular Systems (CIMoS), Institute for Molecular Science, National Institutes of Natural Sciences, Okazaki, Aichi 444-8585, Japan
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Low-Frequency Dynamics of Strongly Correlated Electrons in (BEDT-TTF)2X Studied by Fluctuation Spectroscopy. CRYSTALS 2018. [DOI: 10.3390/cryst8040166] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Fluctuation spectroscopy measurements of quasi-two-dimensional organic charge-transfer salts (BEDT-TTF) 2 X are reviewed. In the past decade, the method has served as a new approach for studying the low-frequency dynamics of strongly correlated charge carriers in these materials. We review some basic aspects of electronic fluctuations in solids, and give an overview of selected problems where the analysis of 1 / f -type fluctuations and the corresponding slow dynamics provide a better understanding of the underlying physics. These examples are related to (1) an inhomogeneous current distribution due to phase separation and/or a percolative transition; (2) slow dynamics due to a glassy freezing either of structural degrees of freedom coupling to the electronic properties or (3) of the electrons themselves, e.g., when residing on a highly-frustrated crystal lattice, where slow and heterogeneous dynamics are key experimental properties for the vitrification process of a supercooled charge-liquid. Another example is (4), the near divergence and critical slowing down of charge carrier fluctuations at the finite-temperature critical endpoint of the Mott metal-insulator transition. Here also indications for a glassy freezing and temporal and spatial correlated dynamics are found. Mapping out the region of ergodicity breaking and understanding the influence of disorder on the temporal and spatial correlated fluctuations will be an important realm of future studies, as well as the fluctuation properties deep in the Mott or charge-ordered insulating states providing a connection to relaxor or ordered ferroelectric states studied by dielectric spectroscopy.
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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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Müller J. Fluctuation Spectroscopy: A New Approach for Studying Low‐Dimensional Molecular Metals. Chemphyschem 2011; 12:1222-45. [DOI: 10.1002/cphc.201000814] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2010] [Indexed: 11/12/2022]
Affiliation(s)
- Jens Müller
- Institute of Physics, Goethe University Frankfurt, Max‐von‐Laue‐Str. 1, 60438 Frankfurt (M) (Germany), Fax: (+49) 69‐798‐47227
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