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Wang Y, Shen Z, Zhang D, Wang L, Tsurkan V, Prodan L, Loidl A, Dumre BB, Khare SV. Pressure-Induced Changes in the Crystal Structure and Electrical Conductivity of GeV 4S 8. CHEMISTRY OF MATERIALS : A PUBLICATION OF THE AMERICAN CHEMICAL SOCIETY 2024; 36:3128-3137. [PMID: 38617806 PMCID: PMC11008103 DOI: 10.1021/acs.chemmater.3c02488] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/02/2023] [Revised: 03/10/2024] [Accepted: 03/11/2024] [Indexed: 04/16/2024]
Abstract
Lacunar spinels, represented by AM4X8 compounds (A = Ga or Ge; M = V, Mo, Nb, or Ta; X = S or Se), form a unique group of ternary chalcogenide compounds. Among them, GeV4S8 has garnered significant attention due to its distinctive electrical and magnetic properties. While previous research efforts have primarily focused on studying how this material behaves under cooling conditions, pressure is another factor that determines the state and characteristics of solid matter. In this study, we employed a diamond anvil cell in conjunction with high-energy synchrotron X-ray diffraction, Raman spectroscopy, four-point probes, and theoretical computation to thoroughly investigate this material. We found that the structural transformation from cubic to orthorhombic was initiated at 34 GPa and completed at 54 GPa. Through data fitting of volume vs pressure, we determined the bulk moduli to be 105 ± 4 GPa for the cubic phase and 111 ± 12 GPa for the orthorhombic phase. Concurrently, electrical resistance measurements indicated a semiconductor-to-nonmetallic conductor transition at ∼15 GPa. Moreover, we experimentally assessed the band gaps at different pressures to validate the occurrence of the electrical phase transition. We infer that the electrical phase transition correlates with the valence electrons in the V4 cluster rather than the crystal structure transformation. Furthermore, the computational results, electronic density of states, and band structure verified the experimental observation and facilitated the understanding of the mechanism governing the electrical phase transition in GeV4S8.
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Affiliation(s)
- Yuejian Wang
- Physics
Department, Oakland University, Rochester, Michigan 48309, United States
| | - Zhiwei Shen
- Center
for
High-Pressure Science (CHiPS), State Key Laboratory of Metastable
Materials Science and Technology, Yanshan
University, Qinhuangdao, Hebei 066004, China
| | - Dongzhou Zhang
- Partnership
for Extreme Crystallography, University
of Hawaii at Manoa, Honolulu, Hawaii 96822, United States
| | - Lin Wang
- Center
for
High-Pressure Science (CHiPS), State Key Laboratory of Metastable
Materials Science and Technology, Yanshan
University, Qinhuangdao, Hebei 066004, China
| | - Vladimir Tsurkan
- Experimental
Physics V, Center for Electronic Correlations and Magnetism, University of Augsburg, Augsburg 86135, Germany
- Institute
of Applied Physics, Moldova State University, MD-2028 Chisinau, Republic of Moldova
| | - Lilian Prodan
- Experimental
Physics V, Center for Electronic Correlations and Magnetism, University of Augsburg, Augsburg 86135, Germany
- Institute
of Applied Physics, Moldova State University, MD-2028 Chisinau, Republic of Moldova
| | - Alois Loidl
- Experimental
Physics V, Center for Electronic Correlations and Magnetism, University of Augsburg, Augsburg 86135, Germany
| | - Bishal B. Dumre
- Department
of Physics and Astronomy, and Wright Center for Photovoltaics Innovation
and Commercialization (PVIC), University
of Toledo, Toledo, Ohio 43606, United States
| | - Sanjay V. Khare
- Department
of Physics and Astronomy, and Wright Center for Photovoltaics Innovation
and Commercialization (PVIC), University
of Toledo, Toledo, Ohio 43606, United States
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2
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Petersen T, Bhattacharyya P, Rößler UK, Hozoi L. Resonating holes vs molecular spin-orbit coupled states in group-5 lacunar spinels. Nat Commun 2023; 14:5218. [PMID: 37633997 PMCID: PMC10460446 DOI: 10.1038/s41467-023-40811-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2023] [Accepted: 08/10/2023] [Indexed: 08/28/2023] Open
Abstract
The valence electronic structure of magnetic centers is one of the factors that determines the characteristics of a magnet. This may refer to orbital degeneracy, as for jeff = 1/2 Kitaev magnets, or near-degeneracy, e.g., involving the third and fourth shells in cuprate superconductors. Here we explore the inner structure of magnetic moments in group-5 lacunar spinels, fascinating materials featuring multisite magnetic units in the form of tetrahedral tetramers. Our quantum chemical analysis reveals a very colorful landscape, much richer than the single-electron, single-configuration description applied so far to all group-5 GaM4X8 chalcogenides, and clarifies the basic multiorbital correlations on M4 tetrahedral clusters: while for V strong correlations yield a wave-function that can be well described in terms of four V4+V3+V3+V3+ resonant valence structures, for Nb and Ta a picture of dressed molecular-orbital jeff = 3/2 entities is more appropriate. These internal degrees of freedom likely shape vibronic couplings, phase transitions, and the magneto-electric properties in each of these systems.
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Affiliation(s)
- Thorben Petersen
- Institute for Theoretical Solid State Physics, Leibniz IFW Dresden, Helmholtzstraße 20, Dresden, D-01069, Germany.
| | - Pritam Bhattacharyya
- Institute for Theoretical Solid State Physics, Leibniz IFW Dresden, Helmholtzstraße 20, Dresden, D-01069, Germany
| | - Ulrich K Rößler
- Institute for Theoretical Solid State Physics, Leibniz IFW Dresden, Helmholtzstraße 20, Dresden, D-01069, Germany
| | - Liviu Hozoi
- Institute for Theoretical Solid State Physics, Leibniz IFW Dresden, Helmholtzstraße 20, Dresden, D-01069, Germany.
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Yang Y, Yu F, Wen X, Gui Z, Zhang Y, Zhan F, Wang R, Ying J, Chen X. Pressure-induced transition from a Mott insulator to a ferromagnetic Weyl metal in La 2O 3Fe 2Se 2. Nat Commun 2023; 14:2260. [PMID: 37081003 PMCID: PMC10119149 DOI: 10.1038/s41467-023-37971-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2022] [Accepted: 04/04/2023] [Indexed: 04/22/2023] Open
Abstract
The insulator-metal transition in Mott insulators, known as the Mott transition, is usually accompanied with various novel quantum phenomena, such as unconventional superconductivity, non-Fermi liquid behavior and colossal magnetoresistance. Here, based on high-pressure electrical transport and XRD measurements, and first-principles calculations, we find that a unique pressure-induced Mott transition from an antiferromagnetic Mott insulator to a ferromagnetic Weyl metal in the iron oxychalcogenide La2O3Fe2Se2 occurs around 37 GPa without structural phase transition. Our theoretical calculations reveal that such an insulator-metal transition is mainly due to the enlarged bandwidth and diminishing of electron correlation at high pressure, fitting well with the experimental data. Moreover, the high-pressure ferromagnetic Weyl metallic phase possesses attractive electronic band structures with six pairs of Weyl points close to the Fermi level, and its topological property can be easily manipulated by the magnetic field. The emergence of Weyl fermions in La2O3Fe2Se2 at high pressure may bridge the gap between nontrivial band topology and Mott insulating states. Our findings not only realize ferromagnetic Weyl fermions associated with the Mott transition, but also suggest pressure as an effective controlling parameter to tune the emergent phenomena in correlated electron systems.
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Affiliation(s)
- Ye Yang
- Department of Physics, and CAS Key Laboratory of Strongly-coupled Quantum Matter Physics, University of Science and Technology of China, Hefei, Anhui, 230026, China
| | - Fanghang Yu
- Department of Physics, and CAS Key Laboratory of Strongly-coupled Quantum Matter Physics, University of Science and Technology of China, Hefei, Anhui, 230026, China
| | - Xikai Wen
- Department of Physics, and CAS Key Laboratory of Strongly-coupled Quantum Matter Physics, University of Science and Technology of China, Hefei, Anhui, 230026, China
| | - Zhigang Gui
- Department of Physics, and CAS Key Laboratory of Strongly-coupled Quantum Matter Physics, University of Science and Technology of China, Hefei, Anhui, 230026, China
| | - Yuqing Zhang
- Department of Physics, and CAS Key Laboratory of Strongly-coupled Quantum Matter Physics, University of Science and Technology of China, Hefei, Anhui, 230026, China
| | - Fangyang Zhan
- Department of physics & Center of Quantum Materials and Devices & Chongqing Key Laboratory for Strongly Coupled Physics, Chongqing University, Chongqing, 400044, China
| | - Rui Wang
- Department of physics & Center of Quantum Materials and Devices & Chongqing Key Laboratory for Strongly Coupled Physics, Chongqing University, Chongqing, 400044, China.
| | - Jianjun Ying
- Department of Physics, and CAS Key Laboratory of Strongly-coupled Quantum Matter Physics, University of Science and Technology of China, Hefei, Anhui, 230026, China.
| | - Xianhui Chen
- Department of Physics, and CAS Key Laboratory of Strongly-coupled Quantum Matter Physics, University of Science and Technology of China, Hefei, Anhui, 230026, China.
- CAS Center for Excellence in Quantum Information and Quantum Physics, Hefei, Anhui, 230026, China.
- Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing, 210093, China.
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Petersen T, Prodan L, Tsurkan V, Krug von Nidda HA, Kézsmárki I, Rößler UK, Hozoi L. How Correlations and Spin-Orbit Coupling Work within Extended Orbitals of Transition-Metal Tetrahedra of 4d/5d Lacunar Spinels. J Phys Chem Lett 2022; 13:1681-1686. [PMID: 35148106 DOI: 10.1021/acs.jpclett.1c04100] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Spin-orbit quartet ground states are associated with rich phenomenology, ranging from multipolar phases in f1 rare-earth borides to magnetism emerging through covalency and vibronic couplings in d1 transition-metal compounds. The latter effect has been studied since the 1960s on t2g1 octahedral ML6 units in both molecular complexes and extended solid-state lattices. Here we analyze the Jeff = 3/2 quartet ground state of larger cubane-like M4L4 entities in lacunar spinels, composed of transition-metal (M) tetrahedra caged by chalcogenide ligands (L). These represent a unique platform where spin-orbit coupling acts on molecular-like, delocalized t2 orbitals. Using quantum chemical methods, we pin down the interplay of spin-orbit couplings in such a setting and many-body physics related to other molecular-like single-electron levels, both below and above the reference t21. We provide a different interpretation of resonant inelastic X-ray scattering data on GaTa4Se8 and, by comparing magnetic susceptibility data with calculated g factors, valuable insights into the important role of vibronic couplings.
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Affiliation(s)
- Thorben Petersen
- Institute for Theoretical Solid State Physics, Leibniz IFW Dresden, Helmholtzstraße 20, D-01069 Dresden, Germany
| | - Lilian Prodan
- Experimental Physics V, Center for Electronic Correlations and Magnetism, Institute of Physics, University of Augsburg, D-86159 Augsburg, Germany
- Institute of Applied Physics, MD 2028 Chişinǎu, R. Moldova
| | - Vladimir Tsurkan
- Experimental Physics V, Center for Electronic Correlations and Magnetism, Institute of Physics, University of Augsburg, D-86159 Augsburg, Germany
- Institute of Applied Physics, MD 2028 Chişinǎu, R. Moldova
| | - Hans-Albrecht Krug von Nidda
- Experimental Physics V, Center for Electronic Correlations and Magnetism, Institute of Physics, University of Augsburg, D-86159 Augsburg, Germany
| | - István Kézsmárki
- Experimental Physics V, Center for Electronic Correlations and Magnetism, Institute of Physics, University of Augsburg, D-86159 Augsburg, Germany
| | - Ulrich K Rößler
- Institute for Theoretical Solid State Physics, Leibniz IFW Dresden, Helmholtzstraße 20, D-01069 Dresden, Germany
| | - Liviu Hozoi
- Institute for Theoretical Solid State Physics, Leibniz IFW Dresden, Helmholtzstraße 20, D-01069 Dresden, Germany
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5
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Li ZX, Geng XY, Wang J, Zhuge F. Emerging Artificial Neuron Devices for Probabilistic Computing. Front Neurosci 2021; 15:717947. [PMID: 34421528 PMCID: PMC8377243 DOI: 10.3389/fnins.2021.717947] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2021] [Accepted: 07/19/2021] [Indexed: 11/13/2022] Open
Abstract
In recent decades, artificial intelligence has been successively employed in the fields of finance, commerce, and other industries. However, imitating high-level brain functions, such as imagination and inference, pose several challenges as they are relevant to a particular type of noise in a biological neuron network. Probabilistic computing algorithms based on restricted Boltzmann machine and Bayesian inference that use silicon electronics have progressed significantly in terms of mimicking probabilistic inference. However, the quasi-random noise generated from additional circuits or algorithms presents a major challenge for silicon electronics to realize the true stochasticity of biological neuron systems. Artificial neurons based on emerging devices, such as memristors and ferroelectric field-effect transistors with inherent stochasticity can produce uncertain non-linear output spikes, which may be the key to make machine learning closer to the human brain. In this article, we present a comprehensive review of the recent advances in the emerging stochastic artificial neurons (SANs) in terms of probabilistic computing. We briefly introduce the biological neurons, neuron models, and silicon neurons before presenting the detailed working mechanisms of various SANs. Finally, the merits and demerits of silicon-based and emerging neurons are discussed, and the outlook for SANs is presented.
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Affiliation(s)
- Zong-xiao Li
- Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo, China
- Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing, China
| | - Xiao-ying Geng
- Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo, China
- School of Materials Science and Engineering, Southwest University of Science and Technology, Mianyang, China
| | - Jingrui Wang
- Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo, China
- School of Electronic and Information Engineering, Ningbo University of Technology, Ningbo, China
| | - Fei Zhuge
- Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo, China
- Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing, China
- Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai, China
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6
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Bauers SR, Tellekamp MB, Roberts DM, Hammett B, Lany S, Ferguson AJ, Zakutayev A, Nanayakkara SU. Metal chalcogenides for neuromorphic computing: emerging materials and mechanisms. NANOTECHNOLOGY 2021; 32:372001. [PMID: 33882467 DOI: 10.1088/1361-6528/abfa51] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/04/2020] [Accepted: 04/21/2021] [Indexed: 06/12/2023]
Abstract
The approaching end of Moore's law scaling has significantly accelerated multiple fields of research including neuromorphic-, quantum-, and photonic computing, each of which possesses unique benefits unobtained through conventional binary computers. One of the most compelling arguments for neuromorphic computing systems is power consumption, noting that computations made in the human brain are approximately 106times more efficient than conventional CMOS logic. This review article focuses on the materials science and physical mechanisms found in metal chalcogenides that are currently being explored for use in neuromorphic applications. We begin by reviewing the key biological signal generation and transduction mechanisms within neuronal components of mammalian brains and subsequently compare with observed experimental measurements in chalcogenides. With robustness and energy efficiency in mind, we will focus on short-range mechanisms such as structural phase changes and correlated electron systems that can be driven by low-energy stimuli, such as temperature or electric field. We aim to highlight fundamental materials research and existing gaps that need to be overcome to enable further integration or advancement of metal chalcogenides for neuromorphic systems.
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Affiliation(s)
- Sage R Bauers
- Materials Science Center, National Renewable Energy Laboratory, 15013 Denver West Parkway, Golden, CO 80401, United States of America
| | - M Brooks Tellekamp
- Materials Science Center, National Renewable Energy Laboratory, 15013 Denver West Parkway, Golden, CO 80401, United States of America
| | - Dennice M Roberts
- Materials Science Center, National Renewable Energy Laboratory, 15013 Denver West Parkway, Golden, CO 80401, United States of America
| | - Breanne Hammett
- Materials Science Center, National Renewable Energy Laboratory, 15013 Denver West Parkway, Golden, CO 80401, United States of America
- Department of Chemistry, Colorado School of Mines, 1500 Illinois Avenue, Golden, CO 80401, United States of America
| | - Stephan Lany
- Materials Science Center, National Renewable Energy Laboratory, 15013 Denver West Parkway, Golden, CO 80401, United States of America
| | - Andrew J Ferguson
- Chemistry and Nanoscience Center, National Renewable Energy Laboratory, 15013 Denver West Parkway, Golden, CO 80401, United States of America
| | - Andriy Zakutayev
- Materials Science Center, National Renewable Energy Laboratory, 15013 Denver West Parkway, Golden, CO 80401, United States of America
| | - Sanjini U Nanayakkara
- Materials Science Center, National Renewable Energy Laboratory, 15013 Denver West Parkway, Golden, CO 80401, United States of America
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7
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Deng H, Zhang J, Jeong MY, Wang D, Hu Q, Zhang S, Sereika R, Nakagawa T, Chen B, Yin X, Xiao H, Hong X, Ren J, Han MJ, Chang J, Weng H, Ding Y, Lin HQ, Mao HK. Metallization of Quantum Material GaTa 4Se 8 at High Pressure. J Phys Chem Lett 2021; 12:5601-5607. [PMID: 34110170 DOI: 10.1021/acs.jpclett.1c01069] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Pressure is a unique thermodynamic variable to explore the phase competitions and novel phases inaccessible at ambient conditions. The resistive switching material GaTa4Se8 displays several quantum phases under pressure, such as a Jeff = 3/2 Mott insulator, a correlated quantum magnetic metal, and d-wave topological superconductivity, which has recently drawn considerable interest. Using high-pressure Raman spectroscopy, X-ray diffraction, extended X-ray absorption, transport measurements, and theoretical calculations, we reveal a complex phase diagram for GaTa4Se8 at pressures exceeding 50 GPa. In this previously unattained pressure regime, GaTa4Se8 ranges from a Mott insulator to a metallic phase and exhibits superconducting phases. In contrast to previous studies, we unveil a hidden correlation between the structural distortion and band gap prior to the insulator-to-metal transition, and the metallic phase shows superconductivity with structural and magnetic properties that are distinctive from the lower-pressure phase. These discoveries highlight that GaTa4Se8 is a unique material to probe novel quantum phases from a structural, metallicity, magnetism, and superconductivity perspective.
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Affiliation(s)
- Hongshan Deng
- Center for High Pressure Science and Technology Advanced Research, Beijing 100094, People's Republic of China
| | - Jianbo Zhang
- Center for High Pressure Science and Technology Advanced Research, Beijing 100094, People's Republic of China
| | - Min Yong Jeong
- Department of Physics, Korea Advanced Institute of Science and Technology, Daejeon 34141, Korea
| | - Dong Wang
- Center for High Pressure Science and Technology Advanced Research, Beijing 100094, People's Republic of China
| | - Qingyang Hu
- Center for High Pressure Science and Technology Advanced Research, Beijing 100094, People's Republic of China
| | - Shuai Zhang
- Beijing National Laboratory for Condensed Matter Physics, and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, People's Republic of China
| | - Raimundas Sereika
- Center for High Pressure Science and Technology Advanced Research, Beijing 100094, People's Republic of China
| | - Takeshi Nakagawa
- Center for High Pressure Science and Technology Advanced Research, Beijing 100094, People's Republic of China
| | - Bijuan Chen
- Center for High Pressure Science and Technology Advanced Research, Beijing 100094, People's Republic of China
| | - Xia Yin
- Center for High Pressure Science and Technology Advanced Research, Beijing 100094, People's Republic of China
| | - Hong Xiao
- Center for High Pressure Science and Technology Advanced Research, Beijing 100094, People's Republic of China
| | - Xinguo Hong
- Center for High Pressure Science and Technology Advanced Research, Beijing 100094, People's Republic of China
| | - Jichang Ren
- Nano and Heterogeneous Materials Center, School of Materials Science and Engineering, Nanjing University of Science and Technology, Nanjing 210094, People's Republic of China
| | - Myung Joon Han
- Department of Physics, Korea Advanced Institute of Science and Technology, Daejeon 34141, Korea
| | - Jun Chang
- College of Physics and Information Technology, Shaanxi Normal University, Xi'an 710119, People's Republic of China
| | - Hongming Weng
- Beijing National Laboratory for Condensed Matter Physics, and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, People's Republic of China
| | - Yang Ding
- Center for High Pressure Science and Technology Advanced Research, Beijing 100094, People's Republic of China
| | - Hai-Qing Lin
- Beijing Computational Science Research Center, Beijing 100084, People's Republic of China
| | - Ho-Kwang Mao
- Center for High Pressure Science and Technology Advanced Research, Beijing 100094, People's Republic of China
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8
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Choi S, Yang J, Wang G. Emerging Memristive Artificial Synapses and Neurons for Energy-Efficient Neuromorphic Computing. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2020; 32:e2004659. [PMID: 33006204 DOI: 10.1002/adma.202004659] [Citation(s) in RCA: 69] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/08/2020] [Revised: 08/12/2020] [Indexed: 06/11/2023]
Abstract
Memristors have recently attracted significant interest due to their applicability as promising building blocks of neuromorphic computing and electronic systems. The dynamic reconfiguration of memristors, which is based on the history of applied electrical stimuli, can mimic both essential analog synaptic and neuronal functionalities. These can be utilized as the node and terminal devices in an artificial neural network. Consequently, the ability to understand, control, and utilize fundamental switching principles and various types of device architectures of the memristor is necessary for achieving memristor-based neuromorphic hardware systems. Herein, a wide range of memristors and memristive-related devices for artificial synapses and neurons is highlighted. The device structures, switching principles, and the applications of essential synaptic and neuronal functionalities are sequentially presented. Moreover, recent advances in memristive artificial neural networks and their hardware implementations are introduced along with an overview of the various learning algorithms. Finally, the main challenges of the memristive synapses and neurons toward high-performance and energy-efficient neuromorphic computing are briefly discussed. This progress report aims to be an insightful guide for the research on memristors and neuromorphic-based computing.
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Affiliation(s)
- Sanghyeon Choi
- KU-KIST Graduate School of Converging Science and Technology, Korea University, 145, Anam-ro, Seongbuk-gu, Seoul, 02841, Republic of Korea
| | - Jehyeon Yang
- KU-KIST Graduate School of Converging Science and Technology, Korea University, 145, Anam-ro, Seongbuk-gu, Seoul, 02841, Republic of Korea
| | - Gunuk Wang
- KU-KIST Graduate School of Converging Science and Technology, Korea University, 145, Anam-ro, Seongbuk-gu, Seoul, 02841, Republic of Korea
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9
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Mokdad J, Knebel G, Marin C, Brison JP, Matei I, Braithwaite D. Probing insulators under pressure. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2020; 91:093902. [PMID: 33003814 DOI: 10.1063/5.0016465] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/04/2020] [Accepted: 08/16/2020] [Indexed: 06/11/2023]
Abstract
Applying pressure on a material can reveal many physical properties and is a very efficient tool to understand its physics. Resistivity measurements have been the ideal probe to study metals under pressure. However, in the case of insulators, resistivity, or conductivity, it is often not the appropriate quantity characterizing the material. In this work, we present a newly developed in situ pressure tuning system that can be used over a wide temperature range (2 K-300 K) and allows changing the pressure at any temperature. We also present AC calorimetry and capacitance/loss measurements under pressure and demonstrate how this combination can be used to characterize a material that is too insulating for standard resistivity techniques.
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Affiliation(s)
- J Mokdad
- Université Grenoble Alpes, CEA, IRIG-Pheliqs, 38000 Grenoble, France
| | - G Knebel
- Université Grenoble Alpes, CEA, IRIG-Pheliqs, 38000 Grenoble, France
| | - C Marin
- Université Grenoble Alpes, CEA, IRIG-Pheliqs, 38000 Grenoble, France
| | - J-P Brison
- Université Grenoble Alpes, CEA, IRIG-Pheliqs, 38000 Grenoble, France
| | - I Matei
- Université Grenoble Alpes, CEA, IRIG-Pheliqs, 38000 Grenoble, France
| | - D Braithwaite
- Université Grenoble Alpes, CEA, IRIG-Pheliqs, 38000 Grenoble, France
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10
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Štefančič A, Holt SJR, Lees MR, Ritter C, Gutmann MJ, Lancaster T, Balakrishnan G. Establishing magneto-structural relationships in the solid solutions of the skyrmion hosting family of materials: GaV 4S 8-ySe y. Sci Rep 2020; 10:9813. [PMID: 32555354 PMCID: PMC7299962 DOI: 10.1038/s41598-020-65676-9] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2019] [Accepted: 04/30/2020] [Indexed: 11/09/2022] Open
Abstract
The GaV4S8-ySey (y = 0 to 8) family of materials have been synthesized in both polycrystalline and single crystal form, and their structural and magnetic properties thoroughly investigated. Each of these materials crystallizes in the F[Formula: see text][Formula: see text]3m space group at ambient temperature. However, in contrast to the end members GaV4S8 and GaV4Se8, that undergo a structural transition to the R3m space group at 42 and 41 K respectively, the solid solutions (y = 1 to 7) retain cubic symmetry down to 1.5 K. In zero applied field the end members of the family order ferromagnetically at 13 K (GaV4S8) and 18 K (GaV4Se8), while the intermediate compounds exhibit a spin-glass-like ground state. We demonstrate that the magnetic structure of GaV4S8 shows localization of spins on the V cations, indicating that a charge ordering mechanism drives the structural phase transition. We conclude that the observation of both structural and ferromagnetic transitions in the end members of the series in zero field is a prerequisite for the stabilization of a skyrmion phase, and discuss how the absence of these transitions in the y = 1 to 7 materials can be explained by their structural properties.
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Affiliation(s)
- Aleš Štefančič
- University of Warwick, Department of Physics, Coventry, CV4 7AL, United Kingdom.
| | - Samuel J R Holt
- University of Warwick, Department of Physics, Coventry, CV4 7AL, United Kingdom
| | - Martin R Lees
- University of Warwick, Department of Physics, Coventry, CV4 7AL, United Kingdom
| | | | - Matthias J Gutmann
- ISIS Facility, Rutherford Appleton Laboratory, Oxfordshire, OX11 0QX, United Kingdom
| | - Tom Lancaster
- Durham University, Department of Physics, South Road, Durham, DH1 3LE, United Kingdom
| | - Geetha Balakrishnan
- University of Warwick, Department of Physics, Coventry, CV4 7AL, United Kingdom.
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11
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Ishikawa H, Yajima T, Matsuo A, Ihara Y, Kindo K. Nonmagnetic Ground States and a Possible Quadrupolar Phase in 4d and 5d Lacunar Spinel Selenides GaM_{4}Se_{8} (M=Nb, Ta). PHYSICAL REVIEW LETTERS 2020; 124:227202. [PMID: 32567900 DOI: 10.1103/physrevlett.124.227202] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/24/2020] [Accepted: 05/12/2020] [Indexed: 06/11/2023]
Abstract
Structural and magnetic properties of cubic spinel selenides GaM_{4}Se_{8} (M=Nb, Ta), which are candidates for the molecular J_{eff}=3/2 Mott insulators, are investigated. The effective magnetic moments are reduced compared to the spin only value, indicating the presence of sizable spin-orbit coupling. GaNb_{4}Se_{8} and GaTa_{4}Se_{8} exhibit phase transitions into the nonmagnetic ground states with orthorhombic and tetragonal structures, respectively, which are robust against magnetic field up to at least 60 T. A cubic-cubic phase transition is observed in GaNb_{4}Se_{8} preceding the magnetic transition, suggesting the existence of a quadrupolar-ordered phase theoretically predicted in the J_{eff}=3/2 Mott insulator.
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Affiliation(s)
- Hajime Ishikawa
- Institute for Solid State Physics, University of Tokyo, Kashiwa, Chiba 277-8581, Japan
| | - Takeshi Yajima
- Institute for Solid State Physics, University of Tokyo, Kashiwa, Chiba 277-8581, Japan
| | - Akira Matsuo
- Institute for Solid State Physics, University of Tokyo, Kashiwa, Chiba 277-8581, Japan
| | - Yoshihiko Ihara
- Department of Physics, Faculty of Science, Hokkaido University, Sapporo 060-0810, Japan
| | - Koichi Kindo
- Institute for Solid State Physics, University of Tokyo, Kashiwa, Chiba 277-8581, Japan
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12
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Neuber E, Milde P, Butykai A, Bordacs S, Nakamura H, Waki T, Tabata Y, Geirhos K, Lunkenheimer P, Kézsmárki I, Ondrejkovic P, Hlinka J, Eng LM. Architecture of nanoscale ferroelectric domains in GaMo 4S 8. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2018; 30:445402. [PMID: 30255852 DOI: 10.1088/1361-648x/aae448] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Local-probe imaging of the ferroelectric domain structure and auxiliary bulk pyroelectric measurements were conducted at low temperatures with the aim to clarify the essential aspects of the orbitally driven phase transition in GaMo4S8, a lacunar spinel crystal that can be viewed as a spin-hole analogue of its GaV4S8 counterpart. We employed multiple scanning probe techniques combined with symmetry and mechanical compatibility analysis to uncover the hierarchical domain structures, developing on the 10-100 nm scale. The identified domain architecture involves a plethora of ferroelectric domain boundaries and junctions, including primary and secondary domain walls in both electrically neutral and charged configurations, and topological line defects transforming neutral secondary walls into two oppositely charged ones.
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Affiliation(s)
- Erik Neuber
- Institute of Applied Physics, Technische Universität Dresden, D-01062 Dresden, Germany
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13
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Direct experimental observation of the molecular J eff = 3/2 ground state in the lacunar spinel GaTa 4Se 8. Nat Commun 2017; 8:782. [PMID: 28978909 PMCID: PMC5627251 DOI: 10.1038/s41467-017-00841-9] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2016] [Accepted: 07/28/2017] [Indexed: 11/08/2022] Open
Abstract
Strong spin–orbit coupling lifts the degeneracy of t2g orbitals in 5d transition-metal systems, leaving a Kramers doublet and quartet with effective angular momentum of Jeff = 1/2 and 3/2, respectively. These spin–orbit entangled states can host exotic quantum phases such as topological Mott state, unconventional superconductivity, and quantum spin liquid. The lacunar spinel GaTa4Se8 was theoretically predicted to form the molecular Jeff = 3/2 ground state. Experimental verification of its existence is an important first step to exploring the consequences of the Jeff = 3/2 state. Here, we report direct experimental evidence of the Jeff = 3/2 state in GaTa4Se8 by means of excitation spectra of resonant inelastic X-ray scattering at the Ta L3 and L2 edges. We find that the excitations involving the Jeff = 1/2 molecular orbital are absent only at the Ta L2 edge, manifesting the realization of the molecular Jeff = 3/2 ground state in GaTa4Se8. The strong interaction between electron spin and orbital degrees of freedom in 5d oxides can lead to exotic electronic ground states. Here the authors use resonant inelastic X-ray scattering to demonstrate that the theoretically proposed Jeff = 3/2 state is realised in GaTa4Se8.
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14
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Haraguchi Y, Michioka C, Ishikawa M, Nakano Y, Yamochi H, Ueda H, Yoshimura K. Magnetic–Nonmagnetic Phase Transition with Interlayer Charge Disproportionation of Nb3 Trimers in the Cluster Compound Nb3Cl8. Inorg Chem 2017; 56:3483-3488. [DOI: 10.1021/acs.inorgchem.6b03028] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Yuya Haraguchi
- Department
of Chemistry, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan
| | - Chishiro Michioka
- Department
of Chemistry, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan
| | - Manabu Ishikawa
- Department
of Chemistry, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan
| | - Yoshiaki Nakano
- Department
of Chemistry, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan
| | - Hideki Yamochi
- Department
of Chemistry, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan
| | - Hiroaki Ueda
- Department
of Chemistry, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan
| | - Kazuyoshi Yoshimura
- Department
of Chemistry, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan
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15
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Ehlers D, Stasinopoulos I, Kézsmárki I, Fehér T, Tsurkan V, von Nidda HAK, Grundler D, Loidl A. Exchange anisotropy in the skyrmion host GaV 4S 8. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2017; 29:065803. [PMID: 28002048 DOI: 10.1088/1361-648x/aa4e7e] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Using ferromagnetic resonance spectroscopy at 34 GHz we explored the magnetic anisotropy of single-crystalline GaV4S8 in the field-polarized magnetic state. We describe the data in terms of an easy-axis type uniaxial anisotropy with an anisotropy constant [Formula: see text] erg cm-3 at 2 K, corresponding to a relative exchange anisotropy [Formula: see text]%, and about [Formula: see text]erg cm-3 near 11 K, i.e. at temperatures where the skyrmion-lattice phase was recently discovered. The relatively large value of K 1 explains the confinement of the skyrmion tubes to the [Formula: see text] easy axes. A distinct set of resonances in the spectra is attributed to the co-existence of different rhombohedral domains. Complementary broadband spectroscopy demonstrates that non-collinear spin states may sensitively be detected by electron spin resonance techniques.
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Affiliation(s)
- D Ehlers
- Experimentalphysik V, Zentrum für elektronische Korrelationen und Magnetismus, Universität Augsburg, 86135 Augsburg, Germany
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16
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Ruff E, Widmann S, Lunkenheimer P, Tsurkan V, Bordács S, Kézsmárki I, Loidl A. Multiferroicity and skyrmions carrying electric polarization in GaV4S8. SCIENCE ADVANCES 2015; 1:e1500916. [PMID: 26702441 PMCID: PMC4681337 DOI: 10.1126/sciadv.1500916] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/10/2015] [Accepted: 09/10/2015] [Indexed: 05/09/2023]
Abstract
Skyrmions are whirl-like topological spin objects with high potential for future magnetic data storage. A fundamental question that is relevant to both basic research and application is whether ferroelectric (FE) polarization can be associated with skyrmions' magnetic texture and whether these objects can be manipulated by electric fields. We study the interplay between magnetism and electric polarization in the lacunar spinel GaV4S8, which undergoes a structural transition associated with orbital ordering at 44 K and reveals a complex magnetic phase diagram below 13 K, including ferromagnetic, cycloidal, and Néel-type skyrmion lattice (SkL) phases. We found that the orbitally ordered phase of GaV4S8 is FE with a sizable polarization of ~1 μC/cm(2). Moreover, we observed spin-driven excess polarizations in all magnetic phases; hence, GaV4S8 hosts three different multiferroic phases with coexisting polar and magnetic order. These include the SkL phase, where we predict a strong spatial modulation of FE polarization close to the skyrmion cores. By taking into account the crystal symmetry and spin patterns of the magnetically ordered phases, we identify exchange striction as the main microscopic mechanism behind the spin-driven FE polarization in each multiferroic phase. Because GaV4S8 is unique among known SkL host materials owing to its polar crystal structure and the observed strong magnetoelectric effect, this study is an important step toward the nondissipative electric field control of skyrmions.
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Affiliation(s)
- Eugen Ruff
- Experimental Physics V, Center for Electronic Correlations and Magnetism, University of Augsburg, Augsburg 86135, Germany
- Corresponding author. E-mail:
| | - Sebastian Widmann
- Experimental Physics V, Center for Electronic Correlations and Magnetism, University of Augsburg, Augsburg 86135, Germany
| | - Peter Lunkenheimer
- Experimental Physics V, Center for Electronic Correlations and Magnetism, University of Augsburg, Augsburg 86135, Germany
| | - Vladimir Tsurkan
- Experimental Physics V, Center for Electronic Correlations and Magnetism, University of Augsburg, Augsburg 86135, Germany
- Institute of Applied Physics, Academy of Sciences of Moldova, Chisinau MD-2028, Republic of Moldova
| | - Sandor Bordács
- Department of Physics, Budapest University of Technology and Economics and MTA-BME Lendület Magneto-Optical Spectroscopy Research Group, Budapest 1111, Hungary
| | - Istvan Kézsmárki
- Experimental Physics V, Center for Electronic Correlations and Magnetism, University of Augsburg, Augsburg 86135, Germany
- Department of Physics, Budapest University of Technology and Economics and MTA-BME Lendület Magneto-Optical Spectroscopy Research Group, Budapest 1111, Hungary
| | - Alois Loidl
- Experimental Physics V, Center for Electronic Correlations and Magnetism, University of Augsburg, Augsburg 86135, Germany
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17
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Kézsmárki I, Bordács S, Milde P, Neuber E, Eng LM, White JS, Rønnow HM, Dewhurst CD, Mochizuki M, Yanai K, Nakamura H, Ehlers D, Tsurkan V, Loidl A. Néel-type skyrmion lattice with confined orientation in the polar magnetic semiconductor GaV4S8. NATURE MATERIALS 2015; 14:1116-1122. [PMID: 26343913 DOI: 10.1038/nmat4402] [Citation(s) in RCA: 142] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/07/2015] [Accepted: 07/21/2015] [Indexed: 06/05/2023]
Abstract
Following the early prediction of the skyrmion lattice (SkL)--a periodic array of spin vortices--it has been observed recently in various magnetic crystals mostly with chiral structure. Although non-chiral but polar crystals with Cnv symmetry were identified as ideal SkL hosts in pioneering theoretical studies, this archetype of SkL has remained experimentally unexplored. Here, we report the discovery of a SkL in the polar magnetic semiconductor GaV4S8 with rhombohedral (C3v) symmetry and easy axis anisotropy. The SkL exists over an unusually broad temperature range compared with other bulk crystals and the orientation of the vortices is not controlled by the external magnetic field, but instead confined to the magnetic easy axis. Supporting theory attributes these unique features to a new Néel-type of SkL describable as a superposition of spin cycloids in contrast to the Bloch-type SkL in chiral magnets described in terms of spin helices.
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Affiliation(s)
- I Kézsmárki
- Department of Physics, Budapest University of Technology and Economics and MTA-BME Lendület Magneto-optical Spectroscopy Research Group, 1111 Budapest, Hungary
- Experimental Physics V, Center for Electronic Correlations and Magnetism, University of Augsburg, 86135 Augsburg, Germany
| | - S Bordács
- Department of Physics, Budapest University of Technology and Economics and MTA-BME Lendület Magneto-optical Spectroscopy Research Group, 1111 Budapest, Hungary
| | - P Milde
- Institut für Angewandte Photophysik, TU Dresden, D-01069 Dresden, Germany
| | - E Neuber
- Institut für Angewandte Photophysik, TU Dresden, D-01069 Dresden, Germany
| | - L M Eng
- Institut für Angewandte Photophysik, TU Dresden, D-01069 Dresden, Germany
| | - J S White
- Laboratory for Neutron Scattering and Imaging, Paul Scherrer Institut, CH-5232 Villigen, Switzerland
| | - H M Rønnow
- Laboratory for Quantum Magnetism, École Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland
| | - C D Dewhurst
- Institut Laue-Langevin, 6 rue Jules Horowitz 38042 Grenoble, France
| | - M Mochizuki
- Department of Physics and Mathematics, Aoyama Gakuin University, Sagamihara, Kanagawa 229-8558, Japan
- PRESTO, Japan Science and Technology Agency, Kawaguchi, Saitama 332-0012, Japan
| | - K Yanai
- Department of Physics and Mathematics, Aoyama Gakuin University, Sagamihara, Kanagawa 229-8558, Japan
| | - H Nakamura
- Department of Materials Science and Engineering, Kyoto University, Kyoto 606-8501, Japan
| | - D Ehlers
- Experimental Physics V, Center for Electronic Correlations and Magnetism, University of Augsburg, 86135 Augsburg, Germany
| | - V Tsurkan
- Experimental Physics V, Center for Electronic Correlations and Magnetism, University of Augsburg, 86135 Augsburg, Germany
- Institute of Applied Physics, Academy of Sciences of Moldova, MD 2028, Chisinau, Republica Moldova
| | - A Loidl
- Experimental Physics V, Center for Electronic Correlations and Magnetism, University of Augsburg, 86135 Augsburg, Germany
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18
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Lv JP, Chen G, Deng Y, Meng ZY. Coulomb Liquid Phases of Bosonic Cluster Mott Insulators on a Pyrochlore Lattice. PHYSICAL REVIEW LETTERS 2015; 115:037202. [PMID: 26230823 DOI: 10.1103/physrevlett.115.037202] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/14/2015] [Indexed: 06/04/2023]
Abstract
Employing large-scale quantum Monte Carlo simulations, we reveal the full phase diagram of the extended Hubbard model of hard-core bosons on the pyrochlore lattice with partial fillings. When the intersite repulsion is dominant, the system is in a cluster Mott insulator phase with an integer number of bosons localized inside the tetrahedral units of the pyrochlore lattice. We show that the full phase diagram contains three cluster Mott insulator phases with 1/4, 1/2, and 3/4 boson fillings, respectively. We further demonstrate that all three cluster Mott insulators are Coulomb liquid phases and its low-energy property is described by the emergent compact U(1) quantum electrodynamics. In addition to measuring the specific heat and entropy of the cluster Mott insulators, we investigate the correlation function of the emergent electric field and verify it is consistent with the compact U(1) quantum electrodynamics description. Our result sheds light on the magnetic properties of various pyrochlore systems, as well as the charge physics of the cluster magnets.
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Affiliation(s)
- Jian-Ping Lv
- Department of Physics, Anhui Normal University, Wuhu 241000, China
| | - Gang Chen
- Collaborative Innovation Center of Advanced Microstructures and Department of Physics and Center for Field Theory and Particle Physics, Fudan University, Shanghai 200433, China
- Department of Physics, University of Toronto, Toronto, Ontario M5S1A7, Canada
| | - Youjin Deng
- Hefei National Laboratory for Physical Sciences at Microscale and Department of Modern Physics, University of Science and Technology of China, Hefei 230027, China
| | - Zi Yang Meng
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
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19
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Chen G, Kee HY, Kim YB. Fractionalized charge excitations in a spin liquid on partially filled pyrochlore lattices. PHYSICAL REVIEW LETTERS 2014; 113:197202. [PMID: 25415920 DOI: 10.1103/physrevlett.113.197202] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/26/2014] [Indexed: 06/04/2023]
Abstract
We study the Mott transition from a metal to cluster Mott insulators in the 1/4- and 1/8-filled pyrochlore lattice systems [corrected]. It is shown that such Mott transitions can arise due to charge localization in clusters or in tetrahedron units, driven by the nearest-neighbor repulsive interaction. The resulting cluster Mott insulator is a quantum spin liquid with a spinon Fermi surface, but at the same time a novel fractionalized charge liquid with charge excitations carrying half the electron charge. There exist two emergent U(1) gauge fields or "photons" that mediate interactions between spinons and charge excitations, and between fractionalized charge excitations themselves, respectively. In particular, it is suggested that the emergent photons associated with the fractionalized charge excitations can be measured in x-ray scattering experiments. Various other experimental signatures of the exotic cluster Mott insulator are discussed in light of candidate materials with partially filled bands on the pyrochlore lattice.
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Affiliation(s)
- Gang Chen
- Department of Physics, University of Toronto, Toronto, Ontario M5S1A7, Canada
| | - Hae-Young Kee
- Department of Physics, University of Toronto, Toronto, Ontario M5S1A7, Canada and Canadian Institute for Advanced Research/Quantum Materials Program, Toronto, Ontario MSG 1Z8, Canada
| | - Yong Baek Kim
- Department of Physics, University of Toronto, Toronto, Ontario M5S1A7, Canada and School of Physics, Korea Institute for Advanced Study, Seoul 130-722, Korea and Canadian Institute for Advanced Research/Quantum Materials Program, Toronto, Ontario MSG 1Z8, Canada
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20
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Singh K, Simon C, Cannuccia E, Lepetit MB, Corraze B, Janod E, Cario L. Orbital-ordering-driven multiferroicity and magnetoelectric coupling in GeV₄S₈. PHYSICAL REVIEW LETTERS 2014; 113:137602. [PMID: 25302917 DOI: 10.1103/physrevlett.113.137602] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/23/2014] [Indexed: 06/04/2023]
Abstract
We report here the discovery of multiferroicity and large magnetoelectric coupling in the type I orbital order system GeV₄S₈. Our study demonstrates that this clustered compound displays a para-ferroelectric transition at 32 K. This transition originates from an orbital ordering which reorganizes the charge within the transition metal clusters. Below the antiferromagnetic transition at 17 K, the application of a magnetic field significantly affects the ferroelectric polarization, revealing thus a large magnetoelectric coupling. Our study suggests that the application of a magnetic field induces a metamagnetic transition which significantly affects the ferroelectric polarization thanks to an exchange striction phenomenon.
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Affiliation(s)
- Kiran Singh
- Laboratoire CRISMAT, CNRS UMR 6508, ENSICAEN, 6 Bd. du Maréchal Juin, 14050 Caen Cedex 4, France
| | - Charles Simon
- Laboratoire CRISMAT, CNRS UMR 6508, ENSICAEN, 6 Bd. du Maréchal Juin, 14050 Caen Cedex 4, France and Institut Laue Langevin, 71 avenue des Martyrs, 38000 Grenoble, France
| | - Elena Cannuccia
- Institut Laue Langevin, 71 avenue des Martyrs, 38000 Grenoble, France
| | - Marie-Bernadette Lepetit
- Institut Laue Langevin, 71 avenue des Martyrs, 38000 Grenoble, France and Institut Néel, CNRS UPR 2940 Département MCBT, 25 avenue des Martyrs, BP 166, 38042 Grenoble Cedex 9, France
| | - Benoit Corraze
- Institut des Matériaux Jean Rouxel, Université de Nantes, CNRS, 2 rue de la houssinière, BP32229, 44322 Nantes Cedex 3, France
| | - Etienne Janod
- Institut des Matériaux Jean Rouxel, Université de Nantes, CNRS, 2 rue de la houssinière, BP32229, 44322 Nantes Cedex 3, France
| | - Laurent Cario
- Institut des Matériaux Jean Rouxel, Université de Nantes, CNRS, 2 rue de la houssinière, BP32229, 44322 Nantes Cedex 3, France
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21
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Camjayi A, Acha C, Weht R, Rodríguez MG, Corraze B, Janod E, Cario L, Rozenberg MJ. First-order insulator-to-metal Mott transition in the paramagnetic 3D system GaTa4Se8. PHYSICAL REVIEW LETTERS 2014; 113:086404. [PMID: 25192113 DOI: 10.1103/physrevlett.113.086404] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/08/2013] [Indexed: 06/03/2023]
Abstract
The nature of the Mott transition in the absence of any symmetry breaking remains a matter of debate. We study the correlation-driven insulator-to-metal transition in the prototypical 3D Mott system GaTa(4)Se(8), as a function of temperature and applied pressure. We report novel experiments on single crystals, which demonstrate that the transition is of first order and follows from the coexistence of two states, one insulating and one metallic, that we toggle with a small bias current. We provide support for our findings by contrasting the experimental data with calculations that combine local density approximation with dynamical mean-field theory, which are in very good agreement.
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Affiliation(s)
- A Camjayi
- Departamento de Física, FCEN, UBA, and IFIBA, CONICET, Pabellón 1, Ciudad Universitaria, 1428 Buenos Aires, Argentina
| | - C Acha
- Departamento de Física, FCEN, UBA, and IFIBA, CONICET, Pabellón 1, Ciudad Universitaria, 1428 Buenos Aires, Argentina
| | - R Weht
- Gerencia de Investigación y Aplicaciones, Comisión Nacional de Energía Atómica (CNEA), Avenida General Paz y Constituyentes, 1650 San Martín, Argentina and Instituto Sábato, Universidad Nacional de San Martín-CNEA, 1650 San Martín, Argentina
| | - M G Rodríguez
- Departamento de Física, FCEN, UBA, and IFIBA, CONICET, Pabellón 1, Ciudad Universitaria, 1428 Buenos Aires, Argentina
| | - B Corraze
- Institut des Matériaux Jean Rouxel (IMN), Université de Nantes, CNRS, 2 rue de la Houssinière, BP32229, 44322 Nantes, France
| | - E Janod
- Institut des Matériaux Jean Rouxel (IMN), Université de Nantes, CNRS, 2 rue de la Houssinière, BP32229, 44322 Nantes, France
| | - L Cario
- Institut des Matériaux Jean Rouxel (IMN), Université de Nantes, CNRS, 2 rue de la Houssinière, BP32229, 44322 Nantes, France
| | - M J Rozenberg
- Laboratoire de Physique des Solides, CNRS-UMR8502, Université de Paris-Sud, Orsay 91405, France
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Spin-orbital entangled molecular jeff states in lacunar spinel compounds. Nat Commun 2014; 5:3988. [PMID: 24889209 DOI: 10.1038/ncomms4988] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2013] [Accepted: 04/29/2014] [Indexed: 11/08/2022] Open
Abstract
The entanglement of the spin and orbital degrees of freedom through the spin-orbit coupling has been actively studied in condensed matter physics. In several iridium oxide systems, the spin-orbital entangled state, identified by the effective angular momentum jeff, can host novel quantum phases. Here we show that a series of lacunar spinel compounds, GaM4X8 (M=Nb, Mo, Ta and W and X=S, Se and Te), gives rise to a molecular jeff state as a new spin-orbital composite on which the low-energy effective Hamiltonian is based. A wide range of electron correlations is accessible by tuning the bandwidth under external and/or chemical pressure, enabling us to investigate the cooperation between spin-orbit coupling and electron correlations. As illustrative examples, a two-dimensional topological insulating phase and an anisotropic spin Hamiltonian are investigated in the weak and strong coupling regimes, respectively. Our finding can provide an ideal platform for exploring jeff physics and the resulting emergent phenomena.
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Dubost V, Cren T, Vaju C, Cario L, Corraze B, Janod E, Debontridder F, Roditchev D. Resistive switching at the nanoscale in the Mott insulator compound GaTa4Se8. NANO LETTERS 2013; 13:3648-3653. [PMID: 23826620 DOI: 10.1021/nl401510p] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
We study the Mott insulator compound GaTa4Se8 in which we previously discovered an electric-field-induced resistive transition. We show that the resistive switching is associated to the appearance of metallic and super-insulating nanodomains by means of scanning tunneling microscopy/spectroscopy (STM/STS). Moreover, we show that local electronic transitions can be controlled at the nanoscale at room temperature using the electric field of the STM tip. This opens the way for possible applications in resistive random access memories (RRAM) devices.
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Affiliation(s)
- Vincent Dubost
- Institut des Nanosciences de Paris, Université Pierre et Marie Curie, CNRS UMR 7588, Paris, France
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24
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Avalanche breakdown in GaTa4Se8−xTex narrow-gap Mott insulators. Nat Commun 2013; 4:1722. [DOI: 10.1038/ncomms2735] [Citation(s) in RCA: 89] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2012] [Accepted: 03/14/2013] [Indexed: 11/08/2022] Open
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Ta Phuoc V, Vaju C, Corraze B, Sopracase R, Perucchi A, Marini C, Postorino P, Chligui M, Lupi S, Janod E, Cario L. Optical conductivity measurements of GaTa4Se8 under high pressure: evidence of a bandwidth-controlled insulator-to-metal Mott transition. PHYSICAL REVIEW LETTERS 2013; 110:037401. [PMID: 23373949 DOI: 10.1103/physrevlett.110.037401] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/27/2012] [Indexed: 06/01/2023]
Abstract
The optical properties of a GaTa(4)Se(8) single crystal are investigated under high pressure. At ambient pressure, the optical conductivity exhibits a charge gap of ≈0.12 eV and a broad midinfrared band at ≈0.55 eV. As pressure is increased, the low energy spectral weight is strongly enhanced and the optical gap is rapidly filled, pointing to an insulator to metal transition around 6 GPa. The overall evolution of the optical conductivity demonstrates that GaTa(4)Se(8) is a Mott insulator which undergoes a bandwidth-controlled Mott metal-insulator transition under pressure, in remarkably good agreement with theory. With the use of our optical data and ab initio band structure calculations, our results were successfully compared to the (U/D, T/D) phase diagram predicted by dynamical mean field theory for strongly correlated systems.
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Affiliation(s)
- V Ta Phuoc
- GREMAN, CNRS UMR 7347-CEA, Université F. Rabelais, UFR Sciences, Tours, France
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Shestopalov MA, Ledneva AY, Cordier S, Hernandez O, Potel M, Roisnel T, Naumov NG, Perrin C. Tetrahedral Mo4 Clusters as Building Blocks for the Design of Clathrate-Related Giant Frameworks. Angew Chem Int Ed Engl 2011. [DOI: 10.1002/ange.201101986] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Shestopalov MA, Ledneva AY, Cordier S, Hernandez O, Potel M, Roisnel T, Naumov NG, Perrin C. Tetrahedral Mo4 Clusters as Building Blocks for the Design of Clathrate-Related Giant Frameworks. Angew Chem Int Ed Engl 2011; 50:7300-3. [DOI: 10.1002/anie.201101986] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2011] [Indexed: 11/11/2022]
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Cario L, Vaju C, Corraze B, Guiot V, Janod E. Electric-field-induced resistive switching in a family of mott insulators: Towards a new class of RRAM memories. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2010; 22:5193-5197. [PMID: 20957700 DOI: 10.1002/adma.201002521] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Affiliation(s)
- Laurent Cario
- Institut des Matériaux Jean Rouxel, Université de Nantes, CNRS, France
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Dorolti E, Cario L, Corraze B, Janod E, Vaju C, Koo HJ, Kan E, Whangbo MH. Half-metallic ferromagnetism and large negative magnetoresistance in the new lacunar spinel GaTi3VS8. J Am Chem Soc 2010; 132:5704-10. [PMID: 20356073 DOI: 10.1021/ja908128b] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The lacunar spinel compounds GaTi(4-x)V(x)S(8) (0 < x < 4), consisting of Ti(4-x)V(x) tetrahedral clusters, were prepared and their structures were determined by powder X-ray diffraction. The electronic structures of GaTi(4-x)V(x)S(8) (x = 0, 1, 2, 3) were examined by density functional calculations, and the electrical resistivity and magnetic susceptibility of these compounds were measured. Our calculations predict that GaTi(3)VS(8) is a ferromagnetic half-metal, and this prediction was confirmed by magnetotransport experiments performed on polycrystalline samples of GaTi(3)VS(8). The latter reveal a large negative magnetoresistance (up to 22% at 2 K), which is consistent with the intergrain tunnelling magnetoresistance expected for powder samples of a ferromagnetic half-metal and indicates the presence of high spin polarization greater than 53% in GaTi(3)VS(8).
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Affiliation(s)
- Eugen Dorolti
- Institut des Materiaux Jean Rouxel (IMN), Université de Nantes, CNRS, 2, rue de la Houssinière, BP 32229, 44322 Nantes Cedex 3, France
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Baskaran G. Impurity band Mott insulators: a new route to high Tc superconductivity. SCIENCE AND TECHNOLOGY OF ADVANCED MATERIALS 2008; 9:044104. [PMID: 27878017 PMCID: PMC5099631 DOI: 10.1088/1468-6996/9/4/044104] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/21/2008] [Revised: 05/13/2009] [Accepted: 02/06/2009] [Indexed: 06/06/2023]
Abstract
Last century witnessed the birth of semiconductor electronics and nanotechnology. The physics behind these revolutionary developments is certain quantum mechanical behaviour of 'impurity state electrons' in crystalline 'band insulators', such as Si, Ge, GaAs and GaN, arising from intentionally added (doped) impurities. The present article proposes that certain collective quantum behaviour of these impurity state electrons, arising from Coulomb repulsions, could lead to superconductivity in a parent band insulator, in a way not suspected before. Impurity band resonating valence bond theory of superconductivity in boron doped diamond, recently proposed by us, suggests possibility of superconductivity emerging from impurity band Mott insulators. We use certain key ideas and insights from the field of high-temperature superconductivity in cuprates and organics. Our suggestion also offers new possibilities in the field of semiconductor electronics and nanotechnology. The current level of sophistication in solid state technology and combinatorial materials science is very well capable of realizing our proposal and discover new superconductors.
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Vaju C, Cario L, Corraze B, Janod E, Dubost V, Cren T, Roditchev D, Braithwaite D, Chauvet O. Electric-Pulse-driven Electronic Phase Separation, Insulator-Metal Transition, and Possible Superconductivity in a Mott Insulator. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2008; 20:2760-2765. [PMID: 25213903 DOI: 10.1002/adma.200702967] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/28/2007] [Revised: 03/11/2008] [Indexed: 06/03/2023]
Abstract
Experimental evidence of a nonvolatile electric-pulse-induced insulator-to-metal transition and possible superconductivity in the Mott insulator GaTa4 Se8 is reported. Scanning tunneling microscopy experiments show that this unconventional response of the system to short electric pulses arises from a nanometer-scale electronic phase separation generated in the bulk material.
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Affiliation(s)
- Cristian Vaju
- Institut des Matériaux Jean Rouxel (IMN) Université de Nantes, CNRS 2 rue de la Houssinière, BP 32229, 44322 Nantes Cedex 3 (France)
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Jakob S, Müller H, Johrendt D, Altmannshofer S, Scherer W, Rayaprol S, Pöttgen R. Structural and magnetic transitions in the Mott insulator GaNb4S8. ACTA ACUST UNITED AC 2007. [DOI: 10.1039/b704943a] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Bichler D, Johrendt D. LDA +U study of the ferromagnetic Mott-Insulator GaMo4S8. Z Anorg Allg Chem 2006. [DOI: 10.1002/zaac.200670113] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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