1
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Ramos SLLM, Carvalho BR, Monteiro Lobato RL, Ribeiro-Soares J, Fantini C, Ribeiro HB, Molino L, Plumadore R, Heinz T, Luican-Mayer A, Pimenta MA. Selective Electron-Phonon Coupling in Dimerized 1T-TaS 2 Revealed by Resonance Raman Spectroscopy. ACS NANO 2023; 17:15883-15892. [PMID: 37556765 DOI: 10.1021/acsnano.3c03902] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/11/2023]
Abstract
The layered transition-metal dichalcogenide material 1T-TaS2 possesses successive phase transitions upon cooling, resulting in strong electron-electron correlation effects and the formation of charge density waves (CDWs). Recently, a dimerized double-layer stacking configuration was shown to form a Peierls-like instability in the electronic structure. To date, no direct evidence for this double-layer stacking configuration using optical techniques has been reported, in particular through Raman spectroscopy. Here, we employ a multiple excitation and polarized Raman spectroscopy to resolve the behavior of phonons and electron-phonon interactions in the commensurate CDW lattice phase of dimerized 1T-TaS2. We observe a distinct behavior from what is predicted for a single layer and probe a richer number of phonon modes that are compatible with the formation of double-layer units (layer dimerization). The multiple-excitation results show a selective coupling of each Raman-active phonon with specific electronic transitions hidden in the optical spectra of 1T-TaS2, suggesting that selectivity in the electron-phonon coupling must also play a role in the CDW order of 1T-TaS2.
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Affiliation(s)
- Sergio L L M Ramos
- Centro de Tecnologia em Nanomateriais e Grafeno (CTNano), Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais 30123-970, Brazil
| | - Bruno R Carvalho
- Departamento de Física, Universidade Federal do Rio Grande do Norte, Natal, Rio Grande do Norte 59078-970, Brazil
| | | | - Jenaina Ribeiro-Soares
- Departamento de Física, Universidade Federal de Lavras, Campus Universitário, PO Box 3037, Lavras, Minas Gerais 37200-000, Brazil
| | - Cristiano Fantini
- Departamento de Física, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais 30123-970, Brazil
| | - Henrique B Ribeiro
- Department of Applied Physics, Stanford University, Stanford, California 94305, United States
| | - Laurent Molino
- Department of Physics, University of Ottawa, Ottawa, Ontario K1N6N5, Canada
| | - Ryan Plumadore
- Department of Physics, University of Ottawa, Ottawa, Ontario K1N6N5, Canada
| | - Tony Heinz
- Department of Applied Physics, Stanford University, Stanford, California 94305, United States
| | - Adina Luican-Mayer
- Department of Physics, University of Ottawa, Ottawa, Ontario K1N6N5, Canada
| | - Marcos A Pimenta
- Centro de Tecnologia em Nanomateriais e Grafeno (CTNano), Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais 30123-970, Brazil
- Departamento de Física, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais 30123-970, Brazil
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2
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Zhao M, Zhao Y, Xi Y, Xu H, Feng H, Xu X, Hao W, Zhou S, Zhao J, Dou SX, Du Y. Electric-Field-Driven Negative Differential Conductance in 2D van der Waals Ferromagnet Fe 3GeTe 2. NANO LETTERS 2021; 21:9233-9239. [PMID: 34709835 DOI: 10.1021/acs.nanolett.1c03123] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Understanding quantum tunneling principles over two-dimensional (2D) van der Waals (vdW) ferromagnets at the atomic level is essential and complementary to the fundamental study of low-dimensional strong correlated systems and is critical for the development of magnetic tunneling devices. Here, we demonstrate a local electric-field controlled negative differential conductance (NDC) in 2D vdW ferromagnet Fe3GeTe2 (FGT) by using scanning tunneling microscopy (STM). The STM reveals that NDC shows an atomic position dependence and can be precisely modulated by altering the tunneling junction. The band shift together with electric-field-driven 3d-orbital occupancy modulates the sensitive magnetic anisotropic energy (MAE) in 2D FGT and consequently leads to electric-field-tunable NDC, which is also verified by theoretical simulation. This work realizes the electric-field-driven NDC in 2D ferromagnet FGT, which paves a way to design and develop applications based on 2D vdW magnets.
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Affiliation(s)
- Mengting Zhao
- School of Physics and BUAA-UOW Joint Research Centre, Beihang University, Beijing 100191, China
- Institute for Superconducting and Electronic Materials (ISEM), Australian Institute for Innovative Materials (AIIM), University of Wollongong, Wollongong, NSW 2500, Australia
| | - Yanyan Zhao
- Key Lab of Materials Modification by Laser, Ion and Electron Beams, Dalian University of Technology, Ministry of Education, Dalian 116024, China
| | - Yilian Xi
- School of Physics and BUAA-UOW Joint Research Centre, Beihang University, Beijing 100191, China
- Institute for Superconducting and Electronic Materials (ISEM), Australian Institute for Innovative Materials (AIIM), University of Wollongong, Wollongong, NSW 2500, Australia
| | - Hang Xu
- School of Physics and BUAA-UOW Joint Research Centre, Beihang University, Beijing 100191, China
| | - Haifeng Feng
- School of Physics and BUAA-UOW Joint Research Centre, Beihang University, Beijing 100191, China
| | - Xun Xu
- School of Physics and BUAA-UOW Joint Research Centre, Beihang University, Beijing 100191, China
- Institute for Superconducting and Electronic Materials (ISEM), Australian Institute for Innovative Materials (AIIM), University of Wollongong, Wollongong, NSW 2500, Australia
| | - Weichang Hao
- School of Physics and BUAA-UOW Joint Research Centre, Beihang University, Beijing 100191, China
| | - Si Zhou
- Institute for Superconducting and Electronic Materials (ISEM), Australian Institute for Innovative Materials (AIIM), University of Wollongong, Wollongong, NSW 2500, Australia
- Key Lab of Materials Modification by Laser, Ion and Electron Beams, Dalian University of Technology, Ministry of Education, Dalian 116024, China
| | - Jijun Zhao
- Key Lab of Materials Modification by Laser, Ion and Electron Beams, Dalian University of Technology, Ministry of Education, Dalian 116024, China
| | - Shi Xue Dou
- School of Physics and BUAA-UOW Joint Research Centre, Beihang University, Beijing 100191, China
- Institute for Superconducting and Electronic Materials (ISEM), Australian Institute for Innovative Materials (AIIM), University of Wollongong, Wollongong, NSW 2500, Australia
| | - Yi Du
- School of Physics and BUAA-UOW Joint Research Centre, Beihang University, Beijing 100191, China
- Institute for Superconducting and Electronic Materials (ISEM), Australian Institute for Innovative Materials (AIIM), University of Wollongong, Wollongong, NSW 2500, Australia
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3
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Zheng C, Hoffmann R, Perkins TS, Calvagna F, Fotovat R, Ferels C, Mohr A, Kremer RK, Köhler J, Simon A, Bu K, Huang F. Synthesis, structure, and magnetic properties of the quaternary oxysulfides Ln
5V3O7S6 (Ln = La, Ce). ZEITSCHRIFT FUR NATURFORSCHUNG SECTION B-A JOURNAL OF CHEMICAL SCIENCES 2021. [DOI: 10.1515/znb-2021-0107] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Abstract
Two rare earth oxysulfides Ln
5V3O7S6 (Ln = La, Ce) have been synthesized and their structures determined. The two isostructural compounds crystallize in the orthorhombic space group Pmmn (no. 59). The structure features one-dimensional edge-sharing VS4O2 octahedron chains parallel to the b axis. The bonding between V and S/O is covalent, and between Ln
3+ and the rest of the matrix ionic. Magnetic susceptibility measurement revealed that V is in a mixed valence state of V3+ and V4+. Its magnetic behavior follows the Curie-Weiss law.
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Affiliation(s)
- Chong Zheng
- Department of Chemistry and Biochemistry , Northern Illinois University , DeKalb , IL , 60115 , USA
| | - Roald Hoffmann
- Department of Chemistry and Chemical Biology , Cornell University , Ithaca , New York 14853 , USA ,
| | - Timothy S. Perkins
- Department of Chemistry , Coker University , Hartsville , SC , 29550 , USA
| | - Frank Calvagna
- Department of Chemistry , Rock Valley College , Rockford , IL , 61114 , USA
| | - Roxanna Fotovat
- Department of Chemistry and Biochemistry , Northern Illinois University , DeKalb , IL , 60115 , USA
| | - Crystal Ferels
- Department of Chemistry and Biochemistry , Northern Illinois University , DeKalb , IL , 60115 , USA
| | - Alyssa Mohr
- Department of Chemistry and Biochemistry , Northern Illinois University , DeKalb , IL , 60115 , USA
| | - Reinhard K. Kremer
- Max-Planck-Institut für Festkörperforschung , Heisenbergstrasse 1 , D-70569 Stuttgart , Germany
| | - Jürgen Köhler
- Max-Planck-Institut für Festkörperforschung , Heisenbergstrasse 1 , D-70569 Stuttgart , Germany
| | - Arndt Simon
- Max-Planck-Institut für Festkörperforschung , Heisenbergstrasse 1 , D-70569 Stuttgart , Germany
| | - Kejun Bu
- Shanghai Institute of Ceramics , Chinese Academy of Sciences , Shanghai , 200050 , P. R. China
| | - Fuqiang Huang
- Shanghai Institute of Ceramics , Chinese Academy of Sciences , Shanghai , 200050 , P. R. China
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4
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Ravnik J, Diego M, Gerasimenko Y, Vaskivskyi Y, Vaskivskyi I, Mertelj T, Vodeb J, Mihailovic D. A time-domain phase diagram of metastable states in a charge ordered quantum material. Nat Commun 2021; 12:2323. [PMID: 33875669 PMCID: PMC8055663 DOI: 10.1038/s41467-021-22646-7] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2020] [Accepted: 03/17/2021] [Indexed: 11/11/2022] Open
Abstract
Metastable self-organized electronic states in quantum materials are of fundamental importance, displaying emergent dynamical properties that may be used in new generations of sensors and memory devices. Such states are typically formed through phase transitions under non-equilibrium conditions and the final state is reached through processes that span a large range of timescales. Conventionally, phase diagrams of materials are thought of as static, without temporal evolution. However, many functional properties of materials arise as a result of complex temporal changes in the material occurring on different timescales. Hitherto, such properties were not considered within the context of a temporally-evolving phase diagram, even though, under non-equilibrium conditions, different phases typically evolve on different timescales. Here, by using time-resolved optical techniques and femtosecond-pulse-excited scanning tunneling microscopy (STM), we track the evolution of the metastable states in a material that has been of wide recent interest, the quasi-two-dimensional dichalcogenide 1T-TaS2. We map out its temporal phase diagram using the photon density and temperature as control parameters on timescales ranging from 10−12 to 103 s. The introduction of a time-domain axis in the phase diagram enables us to follow the evolution of metastable emergent states created by different phase transition mechanisms on different timescales, thus enabling comparison with theoretical predictions of the phase diagram, and opening the way to understanding of the complex ordering processes in metastable materials. Tracking the evolution of non-equilibrium phases requires measurements over a wide range of timescales. Here, using a combination of femtosecond spectroscopy and scanning tunneling microscopy, the authors map out a temporal phase diagram of metastable states in a charge-ordered material 1T-TaS2.
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Affiliation(s)
- Jan Ravnik
- Complex Matter Department, Jozef Stefan Institute, Ljubljana, Slovenia.,Laboratory for Micro and Nanotechnology, Paul Scherrer Institut, Villigen PSI, Switzerland
| | - Michele Diego
- Complex Matter Department, Jozef Stefan Institute, Ljubljana, Slovenia
| | - Yaroslav Gerasimenko
- Complex Matter Department, Jozef Stefan Institute, Ljubljana, Slovenia.,Center of Excellence on Nanoscience and Nanotechnology-Nanocenter (CENN Nanocenter), Ljubljana, Slovenia
| | | | - Igor Vaskivskyi
- Complex Matter Department, Jozef Stefan Institute, Ljubljana, Slovenia.,Center of Excellence on Nanoscience and Nanotechnology-Nanocenter (CENN Nanocenter), Ljubljana, Slovenia
| | - Tomaz Mertelj
- Complex Matter Department, Jozef Stefan Institute, Ljubljana, Slovenia.,Center of Excellence on Nanoscience and Nanotechnology-Nanocenter (CENN Nanocenter), Ljubljana, Slovenia
| | - Jaka Vodeb
- Complex Matter Department, Jozef Stefan Institute, Ljubljana, Slovenia
| | - Dragan Mihailovic
- Complex Matter Department, Jozef Stefan Institute, Ljubljana, Slovenia. .,Center of Excellence on Nanoscience and Nanotechnology-Nanocenter (CENN Nanocenter), Ljubljana, Slovenia. .,Department of Physics, Faculty of Mathematics and Physics, University of Ljubljana, Ljubljana, Slovenia.
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5
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Latt KZ, Schlueter JA, Darancet P, Hla SW. Two-Dimensional Molecular Charge Density Waves in Single-Layer-Thick Islands of a Dirac Fermion System. ACS NANO 2020; 14:8887-8893. [PMID: 32574034 DOI: 10.1021/acsnano.0c03694] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Charge density waves have been intensely studied in inorganic materials such as transition metal dichalcogenides; however their counterpart in organic materials has yet to be explored in detail. Here we report the finding of robust two-dimensional charge density waves in molecular layers formed by α-(BEDT-TTF)2-I3 on a Ag(111) surface. Low-temperature scanning tunneling microscopy images of a multilayer thick α-(BEDT-TTF)2-I3 on a Ag(111) substrate reveal the coexistence of 5a0 × 5a0 and 31a0×31a0 R9° charge density wave patterns commensurate with the underlying molecular lattice at 80 K. Both charge density wave patterns remain in nanosize molecular islands with just a single constituent molecular-layer thickness at 80 and 5 K. Local tunneling spectroscopy measurements reveal the variation of the gap from 244 to 288 meV between the maximum and minimum charge density wave locations. Density functional theory calculations further confirm a vertical positioning of BEDT-TTF molecules in the molecular layer. While the observed charge density wave patterns are stable for the defect sites, they can be reversibly switched for one molecular lattice site by means of inelastic tunneling electron energy transfer with the electron energies exceeding 400 meV using a scanning tunneling microscope manipulation scheme.
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Affiliation(s)
- Kyaw Zin Latt
- Nanoscale and Quantum Phenomena Institute, Physics & Astronomy Department, Ohio University, Athens, Ohio 45701, United States
| | - John A Schlueter
- Division of Materials Research, National Science Foundation, Alexandria, Virginia 22314, United States
| | - Pierre Darancet
- Center for Nanoscale Materials, Argonne National Laboratory, 9700 South Cass Avenue, Lemont, Illinois 60439, United States
| | - Saw-Wai Hla
- Nanoscale and Quantum Phenomena Institute, Physics & Astronomy Department, Ohio University, Athens, Ohio 45701, United States
- Center for Nanoscale Materials, Argonne National Laboratory, 9700 South Cass Avenue, Lemont, Illinois 60439, United States
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