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Hwang J, Ruan W, Chen Y, Tang S, Crommie MF, Shen ZX, Mo SK. Charge density waves in two-dimensional transition metal dichalcogenides. REPORTS ON PROGRESS IN PHYSICS. PHYSICAL SOCIETY (GREAT BRITAIN) 2024; 87:044502. [PMID: 38518359 DOI: 10.1088/1361-6633/ad36d3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/09/2023] [Accepted: 03/22/2024] [Indexed: 03/24/2024]
Abstract
Charge density wave (CDW is one of the most ubiquitous electronic orders in quantum materials. While the essential ingredients of CDW order have been extensively studied, a comprehensive microscopic understanding is yet to be reached. Recent research efforts on the CDW phenomena in two-dimensional (2D) materials provide a new pathway toward a deeper understanding of its complexity. This review provides an overview of the CDW orders in 2D with atomically thin transition metal dichalcogenides (TMDCs) as the materials platform. We mainly focus on the electronic structure investigations on the epitaxially grown TMDC samples with angle-resolved photoemission spectroscopy and scanning tunneling microscopy/spectroscopy as complementary experimental tools. We discuss the possible origins of the 2D CDW, novel quantum states coexisting with them, and exotic types of charge orders that can only be realized in the 2D limit.
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Affiliation(s)
- Jinwoong Hwang
- Department of Physics and Institute of Quantum Convergence Technology, Kangwon National University, Chuncheon 24341, Republic of Korea
| | - Wei Ruan
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200438, People's Republic of China
| | - Yi Chen
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, People's Republic of China
- Collaborative Innovation Center of Quantum Matter, Beijing 100871, People's Republic of China
- Interdisciplinary Institute of Light-Element Quantum Materials and Research Center for Light-Element Advanced Materials, Peking University, Beijing 100871, People's Republic of China
| | - Shujie Tang
- State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050, People's Republic of China
| | - Michael F Crommie
- Department of Physics, University of California, Berkeley, CA, United States of America
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, United States of America
- Kavli Energy NanoSciences Institute at the University of California at Berkeley, Berkeley, CA 94720, United States of America
| | - Zhi-Xun Shen
- Geballe Laboratory for Advanced Materials, Departments of Physics and Applied Physics, Stanford University, Stanford, CA, United States of America
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, CA 94025, United States of America
| | - Sung-Kwan Mo
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA 94720 United States of America
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2
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He D, Zheng Y, Ding D, Ma H, Zhang A, Cheng Y, Zhao W, Jin C. Titanium Self-Intercalation Induced Formation of Orthogonal (1 × 1) Edge/Surface Reconstruction in 1T-TiSe 2: Atomic Scale Dynamics and Mechanistic Study. NANO LETTERS 2024; 24:3835-3841. [PMID: 38498307 DOI: 10.1021/acs.nanolett.4c01040] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/20/2024]
Abstract
Edges and surfaces play indispensable roles in affecting the chemical-physical properties of materials, particularly in two-dimensional transition metal dichalcogenides (TMDCs) with reduced dimensionality. Herein, we report a novel edge/surface structure in multilayer 1T-TiSe2, i.e., the orthogonal (1 × 1) reconstruction, induced by the self-intercalation of Ti atoms into interlayer octahedral sites of the host TiSe2 at elevated temperature. Formation dynamics of the reconstructed edge/surface are captured at the atomic level by in situ scanning transmission electron microscopy (STEM) and further validated by density functional theory (DFT), which enables the proposal of the nucleation mechanism and two growth routes (zigzag and armchair). Via STEM-electron energy loss spectroscopy (STEM-EELS), a chemical shift of 0.6 eV in Ti L3,2 is observed in the reconstructed edge/surface, which is attributed to the change of the coordination number and lattice distortion. The present work provides insights to tailor the atomic/electronic structures and properties of 2D TMDC materials.
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Affiliation(s)
- Daliang He
- State Key Laboratory of Silicon and Advanced Semiconductor Materials, School of Materials Science and Engineering, Zhejiang University, Hangzhou, Zhejiang 310027, P. R. China
- Jihua Laboratory, Foshan, Guangdong 528200, China
| | - Yonghui Zheng
- Key Laboratory of Polar Materials and Devices (MOE), Department of Electronics, East China Normal University, Shanghai 200241, China
| | - Degong Ding
- State Key Laboratory of Silicon and Advanced Semiconductor Materials, School of Materials Science and Engineering, Zhejiang University, Hangzhou, Zhejiang 310027, P. R. China
| | - Hao Ma
- School of Materials Science and Engineering, China University of Petroleum (East China), Qingdao, 266580 Shandong, China
| | - Aixinye Zhang
- School of Materials Science and Engineering, China University of Petroleum (East China), Qingdao, 266580 Shandong, China
| | - Yan Cheng
- Key Laboratory of Polar Materials and Devices (MOE), Department of Electronics, East China Normal University, Shanghai 200241, China
| | - Wen Zhao
- School of Materials Science and Engineering, China University of Petroleum (East China), Qingdao, 266580 Shandong, China
| | - Chuanhong Jin
- State Key Laboratory of Silicon and Advanced Semiconductor Materials, School of Materials Science and Engineering, Zhejiang University, Hangzhou, Zhejiang 310027, P. R. China
- Jihua Laboratory, Foshan, Guangdong 528200, China
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3
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Cohen-Stead B, Bradley O, Miles C, Batrouni G, Scalettar R, Barros K. Fast and scalable quantum Monte Carlo simulations of electron-phonon models. Phys Rev E 2022; 105:065302. [PMID: 35854479 DOI: 10.1103/physreve.105.065302] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2022] [Accepted: 05/31/2022] [Indexed: 06/15/2023]
Abstract
We introduce methodologies for highly scalable quantum Monte Carlo simulations of electron-phonon models, and we report benchmark results for the Holstein model on the square lattice. The determinant quantum Monte Carlo (DQMC) method is a widely used tool for simulating simple electron-phonon models at finite temperatures, but it incurs a computational cost that scales cubically with system size. Alternatively, near-linear scaling with system size can be achieved with the hybrid Monte Carlo (HMC) method and an integral representation of the Fermion determinant. Here, we introduce a collection of methodologies that make such simulations even faster. To combat "stiffness" arising from the bosonic action, we review how Fourier acceleration can be combined with time-step splitting. To overcome phonon sampling barriers associated with strongly bound bipolaron formation, we design global Monte Carlo updates that approximately respect particle-hole symmetry. To accelerate the iterative linear solver, we introduce a preconditioner that becomes exact in the adiabatic limit of infinite atomic mass. Finally, we demonstrate how stochastic measurements can be accelerated using fast Fourier transforms. These methods are all complementary and, combined, may produce multiple orders of magnitude speedup, depending on model details.
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Affiliation(s)
| | - Owen Bradley
- Department of Physics, University of California, Davis, California 95616, USA
| | - Cole Miles
- Department of Physics, Cornell University, Ithaca, New York 14853, USA
| | - George Batrouni
- Université Côte d'Azur, CNRS, Institut de Physique de Nice, (INPHYNI), 06103 Nice, France
- Centre for Quantum Technologies, National University of Singapore, 2 Science Drive 3, 117542 Singapore
- Department of Physics, National University of Singapore, 2 Science Drive 3, 117542 Singapore
| | - Richard Scalettar
- Department of Physics, University of California, Davis, California 95616, USA
| | - Kipton Barros
- Theoretical Division and CNLS, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
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Tayran C, Çakmak M. Charge density wave in a SnSe 2 layer on and the effect of surface hydrogenation. Phys Chem Chem Phys 2022; 24:6820-6827. [PMID: 35244640 DOI: 10.1039/d1cp05569k] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We have carried out an investigation using density functional theory (DFT) of the atomic and electronic structures of SnSe2 layers on the surface and hydrogenation of this surface. We have considered a (2 × 2) SnSe2 superstructure oriented along the diagonal direction of the surface periodicity, for which scanning tunneling microscopy (STM) measurements have recently been reported. In the band structure calculations, while the s-p character surface state originating from each SnSe2 layer is determined, there is an additional half-filled surface state in the fundamental band gap region due to the Sn adatom. At the M̄ point in the Brillouin zone, a charge density wave (CDW) partial gap opening of ∼0.1 eV occurs between these surface states close to the Fermi level. Here, the CDW gap is caused by two reasons; (i) Fermi surface nesting, due to the inequivalent electron pockets at the M̄ point, and (ii) the out of plane weak electron-phonon coupling regime due to the mean-field (MF) theory (2Δ/kBTMF = 3.52). Upon hydrogen adsorption on the surface, we have obtained a β-phase SnSe layer and SeH2 molecule with a bond angle of ∼90°. The hydrogenated surface pushes the surface state associated with the SnSe2 layer into the Si projected bulk band continuum. After SeH2 desorption, the work function drops from 5.20 eV to 4.39 eV.
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Affiliation(s)
- C Tayran
- Department of Physics, Gazi University, Ankara, Turkey.
| | - M Çakmak
- Department of Photonics, Faculty of Applied Sciences, Gazi University, Ankara, Turkey. .,Photonics Application and Research Center, Gazi University, Ankara, Turkey
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Ren MQ, Han S, Fan JQ, Wang L, Wang P, Ren W, Peng K, Li S, Wang SZ, Zheng FW, Zhang P, Li F, Ma X, Xue QK, Song CL. Semiconductor-Metal Phase Transition and Emergent Charge Density Waves in 1 T-ZrX 2 (X = Se, Te) at the Two-Dimensional Limit. NANO LETTERS 2022; 22:476-484. [PMID: 34978815 DOI: 10.1021/acs.nanolett.1c04372] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
A charge density wave (CDW) is a collective quantum phenomenon in metals and features a wavelike modulation of the conduction electron density. A microscopic understanding and experimental control of this many-body electronic state in atomically thin materials remain hot topics in materials physics. By means of material engineering, we realized a dimensionality and Zr intercalation induced semiconductor-metal phase transition in 1T-ZrX2 (X = Se, Te) ultrathin films, accompanied by a commensurate 2 × 2 CDW order. Furthermore, we observed a CDW energy gap of up to 22 meV around the Fermi level. Fourier-transformed scanning tunneling microscopy and angle-resolved photoemission spectroscopy reveal that 1T-ZrX2 films exhibit the simplest Fermi surface among the known CDW materials in TMDCs, consisting only of a Zr 4d derived elliptical electron conduction band at the corners of the Brillouin zone.
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Affiliation(s)
- Ming-Qiang Ren
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, People's Republic of China
| | - Sha Han
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, People's Republic of China
| | - Jia-Qi Fan
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, People's Republic of China
| | - Li Wang
- Vacuum Interconnected Nanotech Workstation, Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences, Suzhou 215123, People's Republic of China
| | - Pengdong Wang
- Vacuum Interconnected Nanotech Workstation, Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences, Suzhou 215123, People's Republic of China
| | - Wei Ren
- Vacuum Interconnected Nanotech Workstation, Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences, Suzhou 215123, People's Republic of China
| | - Kun Peng
- Vacuum Interconnected Nanotech Workstation, Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences, Suzhou 215123, People's Republic of China
| | - Shujing Li
- College of Mathematics and Physics, Beijing University of Chemical Technology, Beijing 100029, People's Republic of China
| | - Shu-Ze Wang
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, People's Republic of China
| | - Fa-Wei Zheng
- Institute of Applied Physics and Computational Mathematics, Beijing 100088, People's Republic of China
| | - Ping Zhang
- College of Mathematics and Physics, Beijing University of Chemical Technology, Beijing 100029, People's Republic of China
| | - Fangsen Li
- Vacuum Interconnected Nanotech Workstation, Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences, Suzhou 215123, People's Republic of China
| | - Xucun Ma
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, People's Republic of China
- Frontier Science Center for Quantum Information, Beijing 100084, People's Republic of China
| | - Qi-Kun Xue
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, People's Republic of China
- Frontier Science Center for Quantum Information, Beijing 100084, People's Republic of China
- Beijing Academy of Quantum Information Sciences, Beijing 100193, People's Republic of China
| | - Can-Li Song
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, People's Republic of China
- Frontier Science Center for Quantum Information, Beijing 100084, People's Republic of China
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Li S, Zhang Z, Xu C, Liu Z, Chen X, Bian Q, Gedeon H, Shao Z, Liu L, Liu Z, Kang N, Cheng HM, Ren W, Pan M. Magnetic Doping Induced Superconductivity-to-Incommensurate Density Waves Transition in a 2D Ultrathin Cr-Doped Mo 2C Crystal. ACS NANO 2021; 15:14938-14946. [PMID: 34469117 DOI: 10.1021/acsnano.1c05133] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
In the vicinity of a competing electronic order, superconductivity emerges within a superconducting dome in the phase diagram, which has been demonstrated in unconventional superconductors and transition-metal dichalcogenides (TMDs), suggesting a scenario where fluctuations or a partial melting of a parent order are essential for inducing superconductivity. Here, we present a contrary example, the two-dimensional (2D) superconductivity in transition-metal carbide can be readily turned into charge density wave (CDW) phases via dilute magnetic doping. Low temperature scanning tunneling microscopy/spectroscopy (STM/STS), transport measurements, and density functional theory (DFT) calculations were employed to investigate Cr-doped superconducting Mo2C crystals in the 2D limit. With ultralow Cr doping (2.7 atom %), the superconductivity of Mo2C is heavily suppressed. Strikingly, an incommensurate density wave (IDW) and a related partially opened gap are observed at a temperature above the superconducting regime. The wave vector of IDW agrees well with the calculated Fermi surface nesting vectors. By further increasing the Cr doping level to 9.4 atom %, a stronger IDW with a smaller periodicity and a larger partial gap appear concurrently. The resistance anomaly implies the onset of the CDW phase. Spatial-resolved and temperature-dependent spectroscopy reveals that such CDW phases exist only in a nonsuperconducting regime and could form long-range orders uniformly. The results provide the understanding for the interplay between charge ordered states and superconductivity in 2D transition-metal carbide.
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Affiliation(s)
- Shaojian Li
- School of Physics, Huazhong University of Science and Technology, Wuhan 430074, P. R. China
| | - Zongyuan Zhang
- School of Physics, Huazhong University of Science and Technology, Wuhan 430074, P. R. China
- Key Laboratory of Structure and Functional Regulation of Hybrid Materials of Ministry of Education, Institutes of Physical Science and Information Technology, Anhui University, Hefei 230601, P. R. China
| | - Chuan Xu
- Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, P. R. China
| | - Zhen Liu
- Key Laboratory for the Physics and Chemistry of Nanodevices and Department of Electronics, Peking University, Beijing 100871, P. R. China
| | - Xiaorui Chen
- School of Physics and Information Technology, Shaanxi Normal University, Xi'an 710119, China
| | - Qi Bian
- School of Physics, Huazhong University of Science and Technology, Wuhan 430074, P. R. China
| | - Habakubaho Gedeon
- School of Physics, Huazhong University of Science and Technology, Wuhan 430074, P. R. China
| | - Zhibin Shao
- School of Physics and Information Technology, Shaanxi Normal University, Xi'an 710119, China
| | - Lijun Liu
- School of Physics, Huazhong University of Science and Technology, Wuhan 430074, P. R. China
| | - Zhibo Liu
- Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, P. R. China
| | - Ning Kang
- Key Laboratory for the Physics and Chemistry of Nanodevices and Department of Electronics, Peking University, Beijing 100871, P. R. China
| | - Hui-Ming Cheng
- Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, P. R. China
- School of Materials Science and Engineering, University of Science and Technology of China, Shenyang 110016, P. R. China
- Shenzhen Geim Graphene Center, Tsinghua-Berkeley Shenzhen Institute (TBSI), Tsinghua University, Shenzhen 518055, P. R. China
| | - Wencai Ren
- Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, P. R. China
- School of Materials Science and Engineering, University of Science and Technology of China, Shenyang 110016, P. R. China
| | - Minghu Pan
- School of Physics, Huazhong University of Science and Technology, Wuhan 430074, P. R. China
- School of Physics and Information Technology, Shaanxi Normal University, Xi'an 710119, China
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7
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Brune V, Grosch M, Weißing R, Hartl F, Frank M, Mishra S, Mathur S. Influence of the choice of precursors on the synthesis of two-dimensional transition metal dichalcogenides. Dalton Trans 2021; 50:12365-12385. [PMID: 34318836 DOI: 10.1039/d1dt01397a] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
The interest in transition metal dichalcogenides (TMDCs; MEy/2; M = transition metal; E = chalcogenide, y = valence of the metal) has grown exponentially across various science and engineering disciplines due to their unique structural chemistry manifested in a two-dimensional lattice that results in extraordinary electronic and transport properties desired for applications in sensors, energy storage and optoelectronic devices. Since the properties of TMDCs can be tailored by changing the stacking sequence of 2D monolayers with similar or dis-similar materials, a number of synthetic routes essentially based on the disintegration of bulk (e.g., chemical exfoliation) or the integration of atomic constituents (e.g., vapor phase growth) have been explored. Despite a large body of data available on the chemical synthesis of TMDCs, experimental strategies with high repeatability of control over film thickness, phase and compositional purity remain elusive, which calls for innovative synthetic concepts offering, for instance, self-limited growth in the z-direction and homogeneous lateral topography. This review summarizes the recent conceptual advancements in the growth of layered van der Waals TMDCs from both mixtures of metal and chalcogen sources (multi-source precursors; MSPs) and from molecular compounds containing metals and chalcogens in one starting material (single-source precursor; SSPs). The critical evaluation of the strengths, limitations and opportunities of MSP and SSP approaches is provided as a guideline for the fabrication of TMDCs from commercial and customized molecular precursors. For example, alternative synthetic pathways using tailored molecular precursors circumvent the challenges of differential nucleation and crystal growth kinetics that are invariably associated with conventional gas phase chemical vapor transport (CVT) and chemical vapor deposition (CVD) of a mixture of components. The aspects of achieving high compositional purity and alternatives to minimize competing reactions or side products are discussed in the context of efficient chemical synthesis of TMDCs. Moreover, a critical analysis of the potential opportunities and existing bottlenecks in the synthesis of TMDCs and their intrinsic properties is provided.
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Affiliation(s)
- Veronika Brune
- Institute of Inorganic Chemistry, University of Cologne, Greinstraße 6, D-50939 Cologne, Germany.
| | - Matthias Grosch
- Institute of Inorganic Chemistry, University of Cologne, Greinstraße 6, D-50939 Cologne, Germany.
| | - René Weißing
- Institute of Inorganic Chemistry, University of Cologne, Greinstraße 6, D-50939 Cologne, Germany.
| | - Fabian Hartl
- Institute of Inorganic Chemistry, University of Cologne, Greinstraße 6, D-50939 Cologne, Germany.
| | - Michael Frank
- Institute of Inorganic Chemistry, University of Cologne, Greinstraße 6, D-50939 Cologne, Germany.
| | - Shashank Mishra
- Université Claude Bernard Lyon 1, CNRS, UMR 5256, IRCELYON, 2 avenue Albert Einstein, 69626 Villeurbanne, France.
| | - Sanjay Mathur
- Institute of Inorganic Chemistry, University of Cologne, Greinstraße 6, D-50939 Cologne, Germany.
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Walmsley TS, Xu YQ. Enhanced photocurrent response speed in charge-density-wave phase of TiSe 2-metal junctions. NANOSCALE 2021; 13:11836-11843. [PMID: 34160523 DOI: 10.1039/d1nr01810h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Group IVB transition metal dichalcogenides (TMDCs) have attracted significant attention due to their predicted high charge carrier mobility, large sheet current density, and enhanced thermoelectric power. Here, we investigate the electrical and optoelectronic properties of few-layer titanium diselenide (TiSe2)-metal junctions through spatial-, wavelength-, temperature-, power- and temporal-dependent scanning photocurrent measurements. Strong photocurrent responses have been detected at TiSe2-metal junctions, which is likely attributed to both photovoltaic and photothermoelectric effects. A fast response time of 31 μs has been achieved, which is two orders of magnitude better than HfSe2 based devices. More importantly, our experimental results reveal a significant enhancement in the response speed upon cooling to the charge-density-wave (CDW) phase transition temperature (TCDW = 206 K), which may result from dramatic reduction in carrier scattering that occurs as a result of the switching between the normal and CDW phases of TiSe2. Additionally, the photoresponsivity at 145 K is up to an order of magnitude higher than that obtained at room temperature. These fundamental studies not only offer insight for the photocurrent generation mechanisms of group IVB TMDC materials, but also provide a route to engineering future temperature-dependent, two-dimensional, fast electronic and optoelectronic devices.
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Affiliation(s)
- Thayer S Walmsley
- Department of Physics and Astronomy, Vanderbilt University, Nashville, TN 37235, USA.
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Lin MK, He T, Hlevyack JA, Chen P, Mo SK, Chou MY, Chiang TC. Coherent Electronic Band Structure of TiTe 2/TiSe 2 Moiré Bilayer. ACS NANO 2021; 15:3359-3364. [PMID: 33570920 DOI: 10.1021/acsnano.0c10352] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
A van der Waals bonded moiré bilayer formed by sequential growth of TiSe2 and TiTe2 monolayers exhibits emergent electronic structure as evidenced by angle-resolved photoemission band mapping. The two monolayers adopt the same lattice orientation but incommensurate lattice constants. Despite the lack of translational symmetry, sharp dispersive bands are observed. The dispersion relations appear distinct from those for the component monolayers alone. Theoretical calculations illustrate the formation of composite bands by coherent electronic coupling despite the weak interlayer bonding, which leads to band renormalization and energy shifts.
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Affiliation(s)
- Meng-Kai Lin
- Department of Physics, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
- Frederick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Tao He
- Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan
| | - Joseph A Hlevyack
- Department of Physics, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
- Frederick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Peng Chen
- Key Laboratory of Artificial Structures and Quantum Control (Ministry of Education), Shenyang National Laboratory for Materials Science, and Shanghai Center for Complex Physics, School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Sung-Kwan Mo
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
| | - Mei-Yin Chou
- Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan
- Department of Physics, National Taiwan University, Taipei 10617, Taiwan
| | - T-C Chiang
- Department of Physics, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
- Frederick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
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10
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Liu W, Duan Z, Zhang C, Hu XX, Cao JB, Liu LJ., Lin L. Experimental observations and density functional simulations on the structural transition behavior of a two-dimensional transition-metal dichalcogenide. Sci Rep 2020; 10:18255. [PMID: 33106537 PMCID: PMC7588463 DOI: 10.1038/s41598-020-75240-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2020] [Accepted: 09/15/2020] [Indexed: 11/29/2022] Open
Abstract
In this work, we show an obvious evidence of nondestructive Raman spectra for the structural transition, i.e., the existence of a charge density wave (CDW) in monolayer 2H-TaS2, which can exhibit a much higher transition temperature than bulk and results in additional vibrational modes, indicating strong interactions with light. Furthermore, we reveal that the degenerate breath and wiggle modes of 2H-TaS2 originated from the periodic lattice distortion can be probed using the optical methods. Since recently several light-tunable devices have been proposed based on the CDW phase transition of 1 T-TaS2, our study and in particular, the theoretical results will be very helpful for understanding and designing electronic devices based on the CDW of 2H-TaS2.
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11
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Lin MK, Hlevyack JA, Chen P, Liu RY, Mo SK, Chiang TC. Charge Instability in Single-Layer TiTe_{2} Mediated by van der Waals Bonding to Substrates. PHYSICAL REVIEW LETTERS 2020; 125:176405. [PMID: 33156647 DOI: 10.1103/physrevlett.125.176405] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/25/2020] [Accepted: 09/10/2020] [Indexed: 06/11/2023]
Abstract
Single layers of transition metal dichalcogenides are of interest for emergent properties; an often-neglected issue is substrate effects. Our experiments show that the charge density wave in a single-layer TiTe_{2} grown on PtTe_{2} films is strongly suppressed by increasing the PtTe_{2} substrate thickness. Given that the interfacial bonding remains of the weak incommensurate van der Waals type, the observed changes are correlated with a thickness-dependent metallicity transformation in the PtTe_{2} substrate. The results illustrate the crucial role of the substrate in single-layer physics.
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Affiliation(s)
- Meng-Kai Lin
- Department of Physics, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
- Frederick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
| | - Joseph A Hlevyack
- Department of Physics, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
- Frederick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
| | - Peng Chen
- Key Laboratory of Artificial Structures and Quantum Control (Ministry of Education), Shenyang National Laboratory for Materials Science and Shanghai Center for Complex Physics, School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Ro-Ya Liu
- Department of Physics, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
- Frederick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
- Institute of Physics, Academia Sinica, Taipei 10617, Taiwan
| | - Sung-Kwan Mo
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - T-C Chiang
- Department of Physics, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
- Frederick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
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12
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Zhang D, Wu Y, Su YH, Hsu MC, Ó Coileáin C, Cho J, Choi M, Chun BS, Guo Y, Chang CR, Wu HC. Charge density waves and degenerate modes in exfoliated monolayer 2H-TaS 2. IUCRJ 2020; 7:913-919. [PMID: 32939283 PMCID: PMC7467171 DOI: 10.1107/s2052252520011021] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/01/2020] [Accepted: 08/11/2020] [Indexed: 06/11/2023]
Abstract
Charge density waves spontaneously breaking lattice symmetry through periodic lattice distortion, and electron-electron and electron-phonon inter-actions, can lead to a new type of electronic band structure. Bulk 2H-TaS2 is an archetypal transition metal dichalcogenide supporting charge density waves with a phase transition at 75 K. Here, it is shown that charge density waves can exist in exfoliated monolayer 2H-TaS2 and the transition temperature can reach 140 K, which is much higher than that in the bulk. The degenerate breathing and wiggle modes of 2H-TaS2 originating from the periodic lattice distortion are probed by optical methods. The results open an avenue to investigating charge density wave phases in two-dimensional transition metal dichalcogenides and will be helpful for understanding and designing devices based on charge density waves.
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Affiliation(s)
- Duan Zhang
- Elementary Educational College, Beijing Key Laboratory for Nano-Photonics and Nano-Structure, Capital Normal University, Beijing 100048, People’s Republic of China
- School of Physics, Beijing Institute of Technology, Beijing 100081, People’s Republic of China
| | - Yecun Wu
- School of Physics, Beijing Institute of Technology, Beijing 100081, People’s Republic of China
| | - Yu-Hsin Su
- Department of Physics, National Taiwan University, Taipei 106, Taiwan
| | - Ming-Chien Hsu
- Department of Physics, National Sun Yat-sen University, Kaohsiung 80424, Taiwan
| | - Cormac Ó Coileáin
- School of Physics, Beijing Institute of Technology, Beijing 100081, People’s Republic of China
| | - Jiung Cho
- Western Seoul Center, Korean Basic Science Institute, Seoul 03579, Republic of Korea
| | - Miri Choi
- Chuncheon Center, Korean Basic Science Institute, Chuncheon 24341, Republic of Korea
| | - Byong Sun Chun
- Division of Industrial Metrology, Korea Research Institute of Standards and Science, Daejeon 3050340, Republic of Korea
| | - Yao Guo
- School of Physics, Beijing Institute of Technology, Beijing 100081, People’s Republic of China
| | - Ching-Ray Chang
- Department of Physics, National Taiwan University, Taipei 106, Taiwan
| | - Han-Chun Wu
- School of Physics, Beijing Institute of Technology, Beijing 100081, People’s Republic of China
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13
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Zhou JS, Monacelli L, Bianco R, Errea I, Mauri F, Calandra M. Anharmonicity and Doping Melt the Charge Density Wave in Single-Layer TiSe 2. NANO LETTERS 2020; 20:4809-4815. [PMID: 32496779 DOI: 10.1021/acs.nanolett.0c00597] [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
Low-dimensional systems with a vanishing band gap and a large electron-hole interaction have been proposed to be unstable toward exciton formation. As the exciton binding energy increases in low dimension, conventional wisdom suggests that excitonic insulators should be more stable in 2D than in 3D. Here we study the effects of the electron-hole interaction and anharmonicity in single-layer TiSe2. We find that, contrary to the bulk case and to the generally accepted picture, in single-layer TiSe2, the electron-hole exchange interaction is much smaller in 2D than in 3D and it has weak effects on phonon spectra. By calculating anharmonic phonon spectra within the stochastic self-consistent harmonic approximation, we obtain TCDW ≈ 440 K for an isolated and undoped single layer and TCDW ≈ 364 K for an electron-doping n = 4.6 × 1013 cm-2, close to the experimental result of 200-280 K on supported samples. Our work demonstrates that anharmonicity and doping melt the charge density wave in single-layer TiSe2.
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Affiliation(s)
- Jianqiang Sky Zhou
- Sorbonne Université, CNRS, Institut des Nanosciences de Paris, UMR7588, F-75252, Paris, France
| | - Lorenzo Monacelli
- Dipartimento di Fisica, Università di Roma Sapienza, Piazzale Aldo Moro 5, I-00185 Roma, Italy
| | - Raffaello Bianco
- Centro de Física de Materiales (CSIC-UPV/EHU), Manuel de Lardizabal pasealekua 5, 20018 Donostia-San Sebastián, Basque Country, Spain
| | - Ion Errea
- Fisika Aplikatua 1 Saila, Gipuzkoako Ingeniaritza Eskola, University of the Basque Country (UPV/EHU), Europa Plaza 1, 20018 Donostia-San Sebastián, Basque Country, Spain
- Centro de Física de Materiales (CSIC-UPV/EHU), Manuel de Lardizabal pasealekua 5, 20018 Donostia-San Sebastián, Basque Country, Spain
- Donostia International Physics Center (DIPC), Manuel de Lardizabal pasealekua 4, 20018 Donostia-San Sebastián, Basque Country, Spain
| | - Francesco Mauri
- Dipartimento di Fisica, Università di Roma La Sapienza, Piazzale Aldo Moro 5, I-00185 Roma, Italy
- Graphene Laboratories, Fondazione Istituto Italiano di Tecnologia, Via Morego, I-16163 Genova, Italy
| | - Matteo Calandra
- Sorbonne Université, CNRS, Institut des Nanosciences de Paris, UMR7588, F-75252, Paris, France
- Department of Physics, University of Trento, Via Sommarive 14, 38123 Povo, Italy
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14
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Lin MK, Villaos RAB, Hlevyack JA, Chen P, Liu RY, Hsu CH, Avila J, Mo SK, Chuang FC, Chiang TC. Dimensionality-Mediated Semimetal-Semiconductor Transition in Ultrathin PtTe_{2} Films. PHYSICAL REVIEW LETTERS 2020; 124:036402. [PMID: 32031832 DOI: 10.1103/physrevlett.124.036402] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/05/2019] [Indexed: 06/10/2023]
Abstract
Platinum ditelluride (PtTe_{2}), a type-II Dirac semimetal, remains semimetallic in ultrathin films down to just two triatomic layers (TLs) with a negative gap of -0.36 eV. Further reduction of the film thickness to a single TL induces a Lifshitz electronic transition to a semiconductor with a large positive gap of +0.79 eV. This transition is evidenced by experimental band structure mapping of films prepared by layer-resolved molecular beam epitaxy, and by comparing the data to first-principles calculations using a hybrid functional. The results demonstrate a novel electronic transition at the two-dimensional limit through film thickness control.
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Affiliation(s)
- Meng-Kai Lin
- Department of Physics, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
- Frederick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
| | | | - Joseph A Hlevyack
- Department of Physics, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
- Frederick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
| | - Peng Chen
- Department of Physics, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
- Frederick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
- Shanghai Center for Complex Physics, School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Ro-Ya Liu
- Department of Physics, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
- Frederick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
- Institute of Physics, Academia Sinica, Taipei 10617, Taiwan
| | - Chia-Hsiu Hsu
- Department of Physics, National Sun Yat-Sen University, Kaohsiung 804, Taiwan
| | - José Avila
- Synchrotron SOLEIL and Universite Paris-Saclay, L'Orme des Merisiers, BP48, 91190 Saint-Aubin, France
| | - Sung-Kwan Mo
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - Feng-Chuan Chuang
- Department of Physics, National Sun Yat-Sen University, Kaohsiung 804, Taiwan
| | - T-C Chiang
- Department of Physics, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
- Frederick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
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15
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Shao Z, Fu ZG, Li S, Cao Y, Bian Q, Sun H, Zhang Z, Gedeon H, Zhang X, Liu L, Cheng Z, Zheng F, Zhang P, Pan M. Strongly Compressed Few-Layered SnSe 2 Films Grown on a SrTiO 3 Substrate: The Coexistence of Charge Ordering and Enhanced Interfacial Superconductivity. NANO LETTERS 2019; 19:5304-5312. [PMID: 31287705 DOI: 10.1021/acs.nanolett.9b01766] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
High pressure has been demonstrated to be a powerful approach of producing novel condensed-matter states, particularly in tuning the superconducting transition temperature (Tc) of the superconductivity in a clean fashion without involving the complexity of chemical doping. However, the challenge of high-pressure experiment hinders further in-depth research for underlying mechanisms. Here, we have successfully synthesized continuous layer-controllable SnSe2 films on SrTiO3 substrate using molecular beam epitaxy. By means of scanning tunneling microscopy/spectroscopy (STM/S) and Raman spectroscopy, we found that the strong compressive strain is intrinsically built in few-layers films, with a largest equivalent pressure up to 23 GPa in the monolayer. Upon this, unusual 2 × 2 charge ordering is induced at the occupied states in the monolayer, accompanied by prominent decrease in the density of states (DOS) near the Fermi energy (EF), resembling the gap states of CDW reported in transition metal dichalcogenide (TMD) materials. Subsequently, the coexistence of charge ordering and the interfacial superconductivity is observed in bilayer films as a result of releasing the compressive strain. In conjunction with spatially resolved spectroscopic study and first-principles calculation, we find that the enhanced interfacial superconductivity with an estimated Tc of 8.3 K is observed only in the 1 × 1 region. Such superconductivity can be ascribed to a combined effect of interfacial charge transfer and compressive strain, which leads to a considerable downshift of the conduction band minimum and an increase in the DOS at EF. Our results provide an attractive platform for further in-depth investigation of compression-induced charge ordering (monolayer) and the interplay between charge ordering and superconductivity (bilayer). Meanwhile, it has opened up a pathway to prepare strongly compressed two-dimensional materials by growing onto a SrTiO3 substrate, which is promising to induce superconductivity with a higher Tc.
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Affiliation(s)
- Zhibin Shao
- School of Physics , Huazhong University of Science and Technology , Wuhan 430074 , China
| | - Zhen-Guo Fu
- Institute of Applied Physics and Computational Mathematics , Beijing 100088 , China
| | - Shaojian Li
- School of Physics , Huazhong University of Science and Technology , Wuhan 430074 , China
| | - Yan Cao
- School of Physics , Huazhong University of Science and Technology , Wuhan 430074 , China
| | - Qi Bian
- School of Physics , Huazhong University of Science and Technology , Wuhan 430074 , China
| | - Haigen Sun
- School of Physics , Huazhong University of Science and Technology , Wuhan 430074 , China
| | - Zongyuan Zhang
- School of Physics , Huazhong University of Science and Technology , Wuhan 430074 , China
| | - Habakubaho Gedeon
- School of Physics , Huazhong University of Science and Technology , Wuhan 430074 , China
| | - Xin Zhang
- School of Physics , Huazhong University of Science and Technology , Wuhan 430074 , China
| | - Lijun Liu
- School of Physics , Huazhong University of Science and Technology , Wuhan 430074 , China
| | - Zhengwang Cheng
- School of Physics , Huazhong University of Science and Technology , Wuhan 430074 , China
| | - Fawei Zheng
- Institute of Applied Physics and Computational Mathematics , Beijing 100088 , China
| | - Ping Zhang
- Institute of Applied Physics and Computational Mathematics , Beijing 100088 , China
| | - Minghu Pan
- School of Physics , Huazhong University of Science and Technology , Wuhan 430074 , China
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16
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Li P, Chen C, Huang Z, Cai Y, Zhang M. The transformation of anatase TiO2 to TiSe2 to form TiO2–TiSe2 composites for Li+/Na+ storage with improved capacities. CrystEngComm 2019. [DOI: 10.1039/c9ce00133f] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
We discovered and explored the basic conditions for the conversion of TiO2-A to TiSe2 and tested its electrochemical performance.
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Affiliation(s)
- Pengchao Li
- Key Laboratory for Micro/Nano Optoelectronic Devices of Ministry of Education & Hunan Provincial Key Laboratory of Low-Dimensional Structural Physics and Devices
- School of Physics and Electronics
- Hunan University
- Changsha 410082
- China
| | - Changmiao Chen
- Key Laboratory for Micro/Nano Optoelectronic Devices of Ministry of Education & Hunan Provincial Key Laboratory of Low-Dimensional Structural Physics and Devices
- School of Physics and Electronics
- Hunan University
- Changsha 410082
- China
| | - Zhao Huang
- Key Laboratory for Micro/Nano Optoelectronic Devices of Ministry of Education & Hunan Provincial Key Laboratory of Low-Dimensional Structural Physics and Devices
- School of Physics and Electronics
- Hunan University
- Changsha 410082
- China
| | - Yong Cai
- Key Laboratory for Micro/Nano Optoelectronic Devices of Ministry of Education & Hunan Provincial Key Laboratory of Low-Dimensional Structural Physics and Devices
- School of Physics and Electronics
- Hunan University
- Changsha 410082
- China
| | - Ming Zhang
- Key Laboratory for Micro/Nano Optoelectronic Devices of Ministry of Education & Hunan Provincial Key Laboratory of Low-Dimensional Structural Physics and Devices
- School of Physics and Electronics
- Hunan University
- Changsha 410082
- China
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17
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Chen C, Singh B, Lin H, Pereira VM. Reproduction of the Charge Density Wave Phase Diagram in 1T-TiSe_{2} Exposes its Excitonic Character. PHYSICAL REVIEW LETTERS 2018; 121:226602. [PMID: 30547625 DOI: 10.1103/physrevlett.121.226602] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/09/2018] [Indexed: 06/09/2023]
Abstract
Recent experiments suggest that excitonic degrees of freedom play an important role in precipitating the charge density wave (CDW) transition in 1T-TiSe_{2}. Through systematic calculations of the electronic and phonon spectrum based on density functional perturbation theory, we show that the predicted critical doping of the CDW phase overshoots the experimental value by 1 order of magnitude. In contrast, an independent self-consistent many-body calculation of the excitonic order parameter and renormalized band structure is able to capture the experimental phase diagram in extremely good qualitative and quantitative agreement. This demonstrates that electron-electron interactions and the excitonic instability arising from direct electron-hole coupling are pivotal to accurately describe the nature of the CDW in this system. This has important implications to understand the emergence of superconductivity within the CDW phase of this and related systems.
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Affiliation(s)
- Chuan Chen
- Centre for Advanced 2D Materials and Graphene Research Centre, National University of Singapore, Singapore 117546
- Department of Physics, National University of Singapore, Singapore 117542
| | - Bahadur Singh
- Centre for Advanced 2D Materials and Graphene Research Centre, National University of Singapore, Singapore 117546
- Department of Physics, National University of Singapore, Singapore 117542
| | - Hsin Lin
- Institute of Physics, Academia Sinica, Taipei 11529, Taiwan
| | - Vitor M Pereira
- Centre for Advanced 2D Materials and Graphene Research Centre, National University of Singapore, Singapore 117546
- Department of Physics, National University of Singapore, Singapore 117542
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18
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Chen P, Pai WW, Chan YH, Madhavan V, Chou MY, Mo SK, Fedorov AV, Chiang TC. Unique Gap Structure and Symmetry of the Charge Density Wave in Single-Layer VSe_{2}. PHYSICAL REVIEW LETTERS 2018; 121:196402. [PMID: 30468619 DOI: 10.1103/physrevlett.121.196402] [Citation(s) in RCA: 45] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/03/2018] [Indexed: 06/09/2023]
Abstract
Single layers of transition metal dichalcogenides (TMDCs) are excellent candidates for electronic applications beyond the graphene platform; many of them exhibit novel properties including charge density waves (CDWs) and magnetic ordering. CDWs in these single layers are generally a planar projection of the corresponding bulk CDWs because of the quasi-two-dimensional nature of TMDCs; a different CDW symmetry is unexpected. We report herein the successful creation of pristine single-layer VSe_{2}, which shows a (sqrt[7]×sqrt[3]) CDW in contrast to the (4×4) CDW for the layers in bulk VSe_{2}. Angle-resolved photoemission spectroscopy from the single layer shows a sizable (sqrt[7]×sqrt[3]) CDW gap of ∼100 meV at the zone boundary, a 220 K CDW transition temperature twice the bulk value, and no ferromagnetic exchange splitting as predicted by theory. This robust CDW with an exotic broken symmetry as the ground state is explained via a first-principles analysis. The results illustrate a unique CDW phenomenon in the two-dimensional limit.
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Affiliation(s)
- P Chen
- Department of Physics, University of Illinois at Urbana-Champaign, 1110 West Green Street, Urbana, Illinois 61801-3080, USA
- Frederick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign, 104 South Goodwin Avenue, Urbana, Illinois 61801-2902, USA
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - Woei Wu Pai
- Center for Condensed Matter Sciences, National Taiwan University, Taipei 10617, Taiwan
- Department of Physics, National Taiwan University, Taipei 10617, Taiwan
| | - Y-H Chan
- Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan
| | - V Madhavan
- Department of Physics, University of Illinois at Urbana-Champaign, 1110 West Green Street, Urbana, Illinois 61801-3080, USA
- Frederick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign, 104 South Goodwin Avenue, Urbana, Illinois 61801-2902, USA
| | - M Y Chou
- Department of Physics, National Taiwan University, Taipei 10617, Taiwan
- Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan
- School of Physics, Georgia Institute of Technology, Atlanta, Georgia 30332, USA
| | - S-K Mo
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - A-V Fedorov
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - T-C Chiang
- Department of Physics, University of Illinois at Urbana-Champaign, 1110 West Green Street, Urbana, Illinois 61801-3080, USA
- Frederick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign, 104 South Goodwin Avenue, Urbana, Illinois 61801-2902, USA
- Department of Physics, National Taiwan University, Taipei 10617, Taiwan
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19
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Han GH, Duong DL, Keum DH, Yun SJ, Lee YH. van der Waals Metallic Transition Metal Dichalcogenides. Chem Rev 2018; 118:6297-6336. [PMID: 29957928 DOI: 10.1021/acs.chemrev.7b00618] [Citation(s) in RCA: 109] [Impact Index Per Article: 18.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Transition metal dichalcogenides are layered materials which are composed of transition metals and chalcogens of the group VIA in a 1:2 ratio. These layered materials have been extensively investigated over synthesis and optical and electrical properties for several decades. It can be insulators, semiconductors, or metals revealing all types of condensed matter properties from a magnetic lattice distorted to superconducting characteristics. Some of these also feature the topological manner. Instead of covering the semiconducting properties of transition metal dichalcogenides, which have been extensively revisited and reviewed elsewhere, here we present the structures of metallic transition metal dichalcogenides and their synthetic approaches for not only high-quality wafer-scale samples using conventional methods (e.g., chemical vapor transport, chemical vapor deposition) but also local small areas by a modification of the materials using Li intercalation, electron beam irradiation, light illumination, pressures, and strains. Some representative band structures of metallic transition metal dichalcogenides and their strong layer-dependence are reviewed and updated, both in theoretical calculations and experiments. In addition, we discuss the physical properties of metallic transition metal dichalcogenides such as periodic lattice distortion, magnetoresistance, superconductivity, topological insulator, and Weyl semimetal. Approaches to overcome current challenges related to these materials are also proposed.
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Affiliation(s)
- Gang Hee Han
- Center for Integrated Nanostructure Physics (CINAP) , Institute for Basic Science (IBS) , Suwon 16419 , Republic of Korea.,Department of Energy Science , Sungkyunkwan University , Suwon 16419 , Republic of Korea
| | - Dinh Loc Duong
- Center for Integrated Nanostructure Physics (CINAP) , Institute for Basic Science (IBS) , Suwon 16419 , Republic of Korea.,Department of Energy Science , Sungkyunkwan University , Suwon 16419 , Republic of Korea
| | - Dong Hoon Keum
- Center for Integrated Nanostructure Physics (CINAP) , Institute for Basic Science (IBS) , Suwon 16419 , Republic of Korea.,Department of Energy Science , Sungkyunkwan University , Suwon 16419 , Republic of Korea
| | - Seok Joon Yun
- Center for Integrated Nanostructure Physics (CINAP) , Institute for Basic Science (IBS) , Suwon 16419 , Republic of Korea.,Department of Energy Science , Sungkyunkwan University , Suwon 16419 , Republic of Korea
| | - Young Hee Lee
- Center for Integrated Nanostructure Physics (CINAP) , Institute for Basic Science (IBS) , Suwon 16419 , Republic of Korea.,Department of Energy Science , Sungkyunkwan University , Suwon 16419 , Republic of Korea.,Department of Physics , Sungkyunkwan University , Suwon 16419 , Republic of Korea
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20
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Wang H, Chen Y, Duchamp M, Zeng Q, Wang X, Tsang SH, Li H, Jing L, Yu T, Teo EHT, Liu Z. Large-Area Atomic Layers of the Charge-Density-Wave Conductor TiSe 2. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2018; 30:1704382. [PMID: 29318716 DOI: 10.1002/adma.201704382] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/03/2017] [Revised: 11/20/2017] [Indexed: 06/07/2023]
Abstract
Layered transition metal (Ti, Ta, Nb, etc.) dichalcogenides are important prototypes for the study of the collective charge density wave (CDW). Reducing the system dimensionality is expected to lead to novel properties, as exemplified by the discovery of enhanced CDW order in ultrathin TiSe2 . However, the syntheses of monolayer and large-area 2D CDW conductors can currently only be achieved by molecular beam epitaxy under ultrahigh vacuum. This study reports the growth of monolayer crystals and up to 5 × 105 µm2 large films of the typical 2D CDW conductor-TiSe2 -by ambient-pressure chemical vapor deposition. Atomic resolution scanning transmission electron microscopy indicates the as-grown samples are highly crystalline 1T-phase TiSe2 . Variable-temperature Raman spectroscopy shows a CDW phase transition temperature of 212.5 K in few layer TiSe2 , indicative of high crystal quality. This work not only allows the exploration of many-body state of TiSe2 in 2D limit but also offers the possibility of utilizing large-area TiSe2 in ultrathin electronic devices.
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Affiliation(s)
- Hong Wang
- School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore, 639798, Singapore
- NOVITAS, Nanoelectronics Centre of Excellence, School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore, 639798, Singapore
- CNRS International NTU Thales Research Alliance (CINTRA), 50 Nanyang Drive, Singapore, 637553, Singapore
| | - Yu Chen
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore, 637371, Singapore
| | - Martial Duchamp
- School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore, 639798, Singapore
| | - Qingsheng Zeng
- School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore, 639798, Singapore
| | - Xuewen Wang
- School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore, 639798, Singapore
| | - Siu Hon Tsang
- Temasek Laboratories@NTU, Nanyang Technological University, Singapore, 637553, Singapore
| | - Hongling Li
- NOVITAS, Nanoelectronics Centre of Excellence, School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore, 639798, Singapore
| | - Lin Jing
- School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore, 639798, Singapore
| | - Ting Yu
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore, 637371, Singapore
| | - Edwin Hang Tong Teo
- School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore, 639798, Singapore
- NOVITAS, Nanoelectronics Centre of Excellence, School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore, 639798, Singapore
- CNRS International NTU Thales Research Alliance (CINTRA), 50 Nanyang Drive, Singapore, 637553, Singapore
| | - Zheng Liu
- School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore, 639798, Singapore
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21
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Yang J, Zhang Y, Zhang Y, Shao J, Geng H, Zhang Y, Zheng Y, Ulaganathan M, Dai Z, Li B, Zong Y, Dong X, Yan Q, Huang W. S-Doped TiSe 2 Nanoplates/Fe 3 O 4 Nanoparticles Heterostructure. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2017; 13:1702181. [PMID: 28922572 DOI: 10.1002/smll.201702181] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/26/2017] [Revised: 08/02/2017] [Indexed: 06/07/2023]
Abstract
2D Sulfur-doped TiSe2 /Fe3 O4 (named as S-TiSe2 /Fe3 O4 ) heterostructures are synthesized successfully based on a facile oil phase process. The Fe3 O4 nanoparticles, with an average size of 8 nm, grow uniformly on the surface of S-doped TiSe2 (named as S-TiSe2 ) nanoplates (300 nm in diameter and 15 nm in thickness). These heterostructures combine the advantages of both S-TiSe2 with good electrical conductivity and Fe3 O4 with high theoretical Li storage capacity. As demonstrated potential applications for energy storage, the S-TiSe2 /Fe3 O4 heterostructures possess high reversible capacities (707.4 mAh g-1 at 0.1 A g-1 during the 100th cycle), excellent cycling stability (432.3 mAh g-1 after 200 cycles at 5 A g-1 ), and good rate capability (e.g., 301.7 mAh g-1 at 20 A g-1 ) in lithium-ion batteries. As for sodium-ion batteries, the S-TiSe2 /Fe3 O4 heterostructures also maintain reversible capacities of 402.3 mAh g-1 at 0.1 A g-1 after 100 cycles, and a high rate capacity of 203.3 mAh g-1 at 4 A g-1 .
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Affiliation(s)
- Jun Yang
- Key Laboratory of Flexible Electronics (KLOFE) and Institute of Advanced Materials (IAM), Jiangsu National Synergetic Innovation Center for Advanced Materials (SICAM), Nanjing Tech University (NanjingTech), 30 South Puzhu Road, Nanjing, 211816, China
| | - Yufei Zhang
- Key Laboratory of Flexible Electronics (KLOFE) and Institute of Advanced Materials (IAM), Jiangsu National Synergetic Innovation Center for Advanced Materials (SICAM), Nanjing Tech University (NanjingTech), 30 South Puzhu Road, Nanjing, 211816, China
| | - Yizhou Zhang
- Key Laboratory of Flexible Electronics (KLOFE) and Institute of Advanced Materials (IAM), Jiangsu National Synergetic Innovation Center for Advanced Materials (SICAM), Nanjing Tech University (NanjingTech), 30 South Puzhu Road, Nanjing, 211816, China
| | - Jinjun Shao
- Key Laboratory of Flexible Electronics (KLOFE) and Institute of Advanced Materials (IAM), Jiangsu National Synergetic Innovation Center for Advanced Materials (SICAM), Nanjing Tech University (NanjingTech), 30 South Puzhu Road, Nanjing, 211816, China
| | - Hongbo Geng
- School of Materials Science and Engineering, Nanyang Technological University, Singapore, 639798, Singapore
| | - Yu Zhang
- School of Materials Science and Engineering, Nanyang Technological University, Singapore, 639798, Singapore
| | - Yun Zheng
- School of Materials Science and Engineering, Nanyang Technological University, Singapore, 639798, Singapore
| | - Mani Ulaganathan
- School of Materials Science and Engineering, Nanyang Technological University, Singapore, 639798, Singapore
| | - Zhengfei Dai
- School of Materials Science and Engineering, Nanyang Technological University, Singapore, 639798, Singapore
| | - Bing Li
- Institute of Materials Research and Engineering A*STAR (Agency for Science, Technology and Research), 2 Fusionopolis Way Innovis #08-03, Singapore, 138634, Singapore
| | - Yun Zong
- Institute of Materials Research and Engineering A*STAR (Agency for Science, Technology and Research), 2 Fusionopolis Way Innovis #08-03, Singapore, 138634, Singapore
| | - Xiaochen Dong
- Key Laboratory of Flexible Electronics (KLOFE) and Institute of Advanced Materials (IAM), Jiangsu National Synergetic Innovation Center for Advanced Materials (SICAM), Nanjing Tech University (NanjingTech), 30 South Puzhu Road, Nanjing, 211816, China
| | - Qingyu Yan
- School of Materials Science and Engineering, Nanyang Technological University, Singapore, 639798, Singapore
| | - Wei Huang
- Key Laboratory of Flexible Electronics (KLOFE) and Institute of Advanced Materials (IAM), Jiangsu National Synergetic Innovation Center for Advanced Materials (SICAM), Nanjing Tech University (NanjingTech), 30 South Puzhu Road, Nanjing, 211816, China
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Emergence of charge density waves and a pseudogap in single-layer TiTe 2. Nat Commun 2017; 8:516. [PMID: 28894137 PMCID: PMC5593837 DOI: 10.1038/s41467-017-00641-1] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2017] [Accepted: 07/17/2017] [Indexed: 11/08/2022] Open
Abstract
Two-dimensional materials constitute a promising platform for developing nanoscale devices and systems. Their physical properties can be very different from those of the corresponding three-dimensional materials because of extreme quantum confinement and dimensional reduction. Here we report a study of TiTe2 from the single-layer to the bulk limit. Using angle-resolved photoemission spectroscopy and scanning tunneling microscopy and spectroscopy, we observed the emergence of a (2 × 2) charge density wave order in single-layer TiTe2 with a transition temperature of 92 ± 3 K. Also observed was a pseudogap of about 28 meV at the Fermi level at 4.2 K. Surprisingly, no charge density wave transitions were observed in two-layer and multi-layer TiTe2, despite the quasi-two-dimensional nature of the material in the bulk. The unique charge density wave phenomenon in the single layer raises intriguing questions that challenge the prevailing thinking about the mechanisms of charge density wave formation. Due to reduced dimensionality, the properties of 2D materials are often different from their 3D counterparts. Here, the authors identify the emergence of a unique charge density wave (CDW) order in monolayer TiTe2 that challenges the current understanding of CDW formation.
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23
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Mo SK. Angle-resolved photoemission spectroscopy for the study of two-dimensional materials. NANO CONVERGENCE 2017; 4:6. [PMCID: PMC6141890 DOI: 10.1186/s40580-017-0100-7] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/23/2017] [Accepted: 03/15/2017] [Indexed: 05/26/2023]
Abstract
Quantum systems in confined geometries allow novel physical properties that cannot easily be attained in their bulk form. These properties are governed by the changes in the band structure and the lattice symmetry, and most pronounced in their single layer limit. Angle-resolved photoemission spectroscopy (ARPES) is a direct tool to investigate the underlying changes of band structure to provide essential information for understanding and controlling such properties. In this review, recent progresses in ARPES as a tool to study two-dimensional atomic crystals have been presented. ARPES results from few-layer and bulk crystals of material class often referred as “beyond graphene” are discussed along with the relevant developments in the instrumentation.
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Affiliation(s)
- Sung-Kwan Mo
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA 94720 USA
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