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Lee S, Jin KH, Jung H, Fukutani K, Lee J, Kwon CI, Kim JS, Kim J, Yeom HW. Surface Doping and Dual Nature of the Band Gap in Excitonic Insulator Ta 2NiSe 5. ACS NANO 2024; 18:24784-24791. [PMID: 39178330 PMCID: PMC11394347 DOI: 10.1021/acsnano.4c02784] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/25/2024]
Abstract
Excitons in semiconductors and molecules are widely utilized in photovoltaics and optoelectronics, and high-temperature coherent quantum states of excitons can be realized in artificial electron-hole bilayers and an exotic material of an excitonic insulator (EI). Here, we investigate the band gap evolution of a putative high-temperature EI Ta2NiSe5 upon surface doing by alkali adsorbates with angle-resolved photoemission and density functional theory (DFT) calculations. The conduction band of Ta2NiSe5 is filled by the charge transfer from alkali adsorbates, and the band gap decreases drastically upon the increase of metallic electron density. Our DFT calculation, however, reveals that there exist both structural and excitonic contributions to the band gap tuned. While electron doping reduces the band gap substantially, it alone is not enough to close the band gap. In contrast, the structural distortion induced by the alkali adsorbate plays a critical role in the gap closure. This work indicates a combined electronic and structural nature for the EI phase of the present system and the complexity of surface doping beyond charge transfer.
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Affiliation(s)
- Siwon Lee
- Center for Artificial Low Dimensional Electronic Systems, Institute for Basic Science (IBS), Pohang 37673, Republic of Korea
- Department of Physics, Pohang University of Science and Technology (POSTECH), Pohang 37673, Republic of Korea
| | - Kyung-Hwan Jin
- Center for Artificial Low Dimensional Electronic Systems, Institute for Basic Science (IBS), Pohang 37673, Republic of Korea
- Department of Physics and Research Institute of Physics and Chemistry, Jeonbuk National University, Jeonju 54896, Republic of Korea
| | - Hyunjin Jung
- Center for Artificial Low Dimensional Electronic Systems, Institute for Basic Science (IBS), Pohang 37673, Republic of Korea
- Department of Physics, Pohang University of Science and Technology (POSTECH), Pohang 37673, Republic of Korea
| | - Keisuke Fukutani
- Center for Artificial Low Dimensional Electronic Systems, Institute for Basic Science (IBS), Pohang 37673, Republic of Korea
| | - Jinwon Lee
- Center for Artificial Low Dimensional Electronic Systems, Institute for Basic Science (IBS), Pohang 37673, Republic of Korea
- Department of Physics, Pohang University of Science and Technology (POSTECH), Pohang 37673, Republic of Korea
- Department of Quantum Nanoscience, Kavli Institute of Nanoscience, Delft University of Technology, Delft 2628 CJ, The Netherlands
| | - Chang Il Kwon
- Center for Artificial Low Dimensional Electronic Systems, Institute for Basic Science (IBS), Pohang 37673, Republic of Korea
- Department of Physics, Pohang University of Science and Technology (POSTECH), Pohang 37673, Republic of Korea
| | - Jun Sung Kim
- Center for Artificial Low Dimensional Electronic Systems, Institute for Basic Science (IBS), Pohang 37673, Republic of Korea
- Department of Physics, Pohang University of Science and Technology (POSTECH), Pohang 37673, Republic of Korea
| | - Jaeyoung Kim
- Center for Artificial Low Dimensional Electronic Systems, Institute for Basic Science (IBS), Pohang 37673, Republic of Korea
| | - Han Woong Yeom
- Center for Artificial Low Dimensional Electronic Systems, Institute for Basic Science (IBS), Pohang 37673, Republic of Korea
- Department of Physics, Pohang University of Science and Technology (POSTECH), Pohang 37673, Republic of Korea
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2
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Choi D, Yue C, Azoury D, Porter Z, Chen J, Petocchi F, Baldini E, Lv B, Mogi M, Su Y, Wilson SD, Eckstein M, Werner P, Gedik N. Light-induced insulator-metal transition in Sr 2IrO 4 reveals the nature of the insulating ground state. Proc Natl Acad Sci U S A 2024; 121:e2323013121. [PMID: 38976737 PMCID: PMC11260128 DOI: 10.1073/pnas.2323013121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2024] [Accepted: 06/07/2024] [Indexed: 07/10/2024] Open
Abstract
Sr2IrO4 has attracted considerable attention due to its structural and electronic similarities to La2CuO4, the parent compound of high-Tc superconducting cuprates. It was proposed as a strong spin-orbit-coupled Jeff = 1/2 Mott insulator, but the Mott nature of its insulating ground state has not been conclusively established. Here, we use ultrafast laser pulses to realize an insulator-metal transition in Sr2IrO4 and probe the resulting dynamics using time- and angle-resolved photoemission spectroscopy. We observe a gap closure and the formation of weakly renormalized electronic bands in the gap region. Comparing these observations to the expected temperature and doping evolution of Mott gaps and Hubbard bands provides clear evidence that the insulating state does not originate from Mott correlations. We instead propose a correlated band insulator picture, where antiferromagnetic correlations play a key role in the gap opening. More broadly, our results demonstrate that energy-momentum-resolved nonequilibrium dynamics can be used to clarify the nature of equilibrium states in correlated materials.
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Affiliation(s)
- Dongsung Choi
- Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, MA02139
| | - Changming Yue
- Department of Physics, University of Fribourg, Fribourg1700, Switzerland
- Department of Physics, Southern University of Science and Technology, Shenzhen518055, People’s Republic of China
| | - Doron Azoury
- Department of Physics, Massachusetts Institute of Technology, Cambridge, MA02139
| | - Zachary Porter
- Materials Department, University of California Santa Barbara, Santa Barbara, CA93106
- Stanford Linear Accelerator Center (SLAC) National Accelerator Laboratory, Stanford University, Stanford, CA94025
| | - Jiyu Chen
- Department of Physics, University of Fribourg, Fribourg1700, Switzerland
| | - Francesco Petocchi
- Department of Physics, University of Fribourg, Fribourg1700, Switzerland
| | - Edoardo Baldini
- Department of Physics, Massachusetts Institute of Technology, Cambridge, MA02139
- Department of Physics, The University of Texas at Austin, Austin, TX78705
| | - Baiqing Lv
- Department of Physics, Massachusetts Institute of Technology, Cambridge, MA02139
- School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai200240, People’s Republic of China
| | - Masataka Mogi
- Department of Physics, Massachusetts Institute of Technology, Cambridge, MA02139
- Department of Applied Physics, University of Tokyo, Bunkyo-ku, Tokyo113-8656, Japan
| | - Yifan Su
- Department of Physics, Massachusetts Institute of Technology, Cambridge, MA02139
| | - Stephen D. Wilson
- Materials Department, University of California Santa Barbara, Santa Barbara, CA93106
| | - Martin Eckstein
- Department of Physics, University of Erlangen-Nürnberg, Erlangen91058, Germany
- Institute of Theoretical Physics, University of Hamburg, Hamburg20355, Germany
| | - Philipp Werner
- Department of Physics, University of Fribourg, Fribourg1700, Switzerland
| | - Nuh Gedik
- Department of Physics, Massachusetts Institute of Technology, Cambridge, MA02139
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3
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Li Q, Chen Y, Wei L, Chen H, Huang Y, Zhu Y, Zhu W, An D, Song J, Gan Q, Zhang Q, Watanabe K, Taniguchi T, Shi X, Novoselov KS, Wang R, Yu G, Wang L. Strongly coupled magneto-exciton condensates in large-angle twisted double bilayer graphene. Nat Commun 2024; 15:5065. [PMID: 38871728 DOI: 10.1038/s41467-024-49406-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2023] [Accepted: 05/31/2024] [Indexed: 06/15/2024] Open
Abstract
Excitons, pairs of electrons and holes, undergo a Bose-Einstein condensation at low temperatures. An important platform to study excitons is double-layer two-dimensional electron gases, with two parallel planes of electrons and holes separated by a thin insulating layer. Lowering this separation (d) strengthens the exciton binding energy, however, leads to the undesired interlayer tunneling, resulting in annihilation of excitons. Here, we report the observation of a sequences of robust exciton condensates (ECs) in double bilayer graphene twisted to ~ 10° with no insulating mid-layer. The large momentum mismatch between two graphene layers suppresses interlayer tunneling, reaching a d ~ 0.334 nm. Measuring the bulk and edge transport, we find incompressible states corresponding to ECs when both layers are in half-filled N = 0, 1 Landau levels (LLs). Theoretical calculations suggest that the low-energy charged excitation of ECs can be meron-antimeron or particle-hole pair, which relies on both LL index and carrier type. Our results establish a novel platform with extreme coupling strength for studying quantum bosonic phase.
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Affiliation(s)
- Qingxin Li
- National Laboratory of Solid-State Microstructures, School of Physics, Nanjing University, Nanjing, 210093, China
| | - Yiwei Chen
- National Laboratory of Solid-State Microstructures, School of Physics, Nanjing University, Nanjing, 210093, China
| | - LingNan Wei
- National Laboratory of Solid-State Microstructures, School of Physics, Nanjing University, Nanjing, 210093, China
| | - Hong Chen
- National Laboratory of Solid-State Microstructures, School of Physics, Nanjing University, Nanjing, 210093, China
| | - Yan Huang
- National Laboratory of Solid-State Microstructures, School of Physics, Nanjing University, Nanjing, 210093, China
| | - Yujian Zhu
- National Laboratory of Solid-State Microstructures, School of Physics, Nanjing University, Nanjing, 210093, China
| | - Wang Zhu
- National Laboratory of Solid-State Microstructures, School of Physics, Nanjing University, Nanjing, 210093, China
| | - Dongdong An
- National Laboratory of Solid-State Microstructures, School of Physics, Nanjing University, Nanjing, 210093, China
| | - Junwei Song
- National Laboratory of Solid-State Microstructures, School of Physics, Nanjing University, Nanjing, 210093, China
| | - Qikang Gan
- National Laboratory of Solid-State Microstructures, School of Physics, Nanjing University, Nanjing, 210093, China
| | - Qi Zhang
- National Laboratory of Solid-State Microstructures, School of Physics, Nanjing University, Nanjing, 210093, China
| | - Kenji Watanabe
- Research Center for Electronic and Optical Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba, 305-0044, Japan
| | - Takashi Taniguchi
- Research Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba, 305-0044, Japan
| | - Xiaoyang Shi
- Environmental and Sustainable Engineering, College of Engineering and Applied Science, University at Albany, Albany, NY, 12222, USA.
| | - Kostya S Novoselov
- Institute for Functional Intelligent Materials, National University of Singapore, Building S9, 4 Science Drive 2, Singapore, 117544, Singapore
| | - Rui Wang
- National Laboratory of Solid-State Microstructures, School of Physics, Nanjing University, Nanjing, 210093, China.
| | - Geliang Yu
- National Laboratory of Solid-State Microstructures, School of Physics, Nanjing University, Nanjing, 210093, China.
| | - Lei Wang
- National Laboratory of Solid-State Microstructures, School of Physics, Nanjing University, Nanjing, 210093, China.
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4
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Haque SRU, Michael MH, Zhu J, Zhang Y, Windgätter L, Latini S, Wakefield JP, Zhang GF, Zhang J, Rubio A, Checkelsky JG, Demler E, Averitt RD. Terahertz parametric amplification as a reporter of exciton condensate dynamics. NATURE MATERIALS 2024; 23:796-802. [PMID: 38172546 DOI: 10.1038/s41563-023-01755-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/27/2022] [Accepted: 11/06/2023] [Indexed: 01/05/2024]
Abstract
Condensates are a hallmark of emergence in quantum materials such as superconductors and charge density waves. Excitonic insulators are an intriguing addition to this library, exhibiting spontaneous condensation of electron-hole pairs. However, condensate observables can be obscured through parasitic coupling to the lattice. Here we employ nonlinear terahertz spectroscopy to disentangle such obscurants through measurement of the quantum dynamics. We target Ta2NiSe5, a putative room-temperature excitonic insulator in which electron-lattice coupling dominates the structural transition (Tc = 326 K), hindering identification of excitonic correlations. A pronounced increase in the terahertz reflectivity manifests following photoexcitation and exhibits a Bose-Einstein condensation-like temperature dependence well below the Tc, suggesting an approach to monitor the exciton condensate dynamics. Nonetheless, dynamic condensate-phonon coupling remains as evidenced by peaks in the enhanced reflectivity spectrum at select infrared-active phonon frequencies, indicating that parametric reflectivity enhancement arises from phonon squeezing. Our results highlight that coherent dynamics can drive parametric stimulated emission.
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Affiliation(s)
- Sheikh Rubaiat Ul Haque
- Department of Physics, University of California San Diego, La Jolla, CA, USA
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, CA, USA
| | | | - Junbo Zhu
- Department of Physics, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Yuan Zhang
- Department of Physics, University of California San Diego, La Jolla, CA, USA
| | - Lukas Windgätter
- Max Planck Institute for the Structure and Dynamics of Matter (MPSD), Hamburg, Germany
| | - Simone Latini
- Max Planck Institute for the Structure and Dynamics of Matter (MPSD), Hamburg, Germany
| | - Joshua P Wakefield
- Department of Physics, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Gu-Feng Zhang
- Department of Physics, University of California San Diego, La Jolla, CA, USA
| | - Jingdi Zhang
- Department of Physics, University of California San Diego, La Jolla, CA, USA
- Department of Physics, The Hong Kong University of Science and Technology, Hongkong, China
| | - Angel Rubio
- Max Planck Institute for the Structure and Dynamics of Matter (MPSD), Hamburg, Germany
- Center for Computational Quantum Physics, The Flatiron Institute, New York, NY, USA
| | - Joseph G Checkelsky
- Department of Physics, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Eugene Demler
- Department of Physics, Harvard University, Cambridge, MA, USA
- Institute for Theoretical Physics, ETH Zürich, Zürich, Switzerland
| | - Richard D Averitt
- Department of Physics, University of California San Diego, La Jolla, CA, USA.
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5
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Li B, Li J, Jiang W, Wang Y, Wang D, Song L, Zhu Y, Wu H, Wang G, Zhang Z. Anisotropic Fracture of Two-Dimensional Ta 2NiSe 5. NANO LETTERS 2024; 24:6344-6352. [PMID: 38687224 DOI: 10.1021/acs.nanolett.4c01202] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2024]
Abstract
Anisotropic two-dimensional materials present a diverse range of physical characteristics, making them well-suited for applications in photonics and optoelectronics. While mechanical properties play a crucial role in determining the reliability and efficacy of 2D material-based devices, the fracture behavior of anisotropic 2D crystals remains relatively unexplored. Toward this end, we herein present the first measurement of the anisotropic fracture toughness of 2D Ta2NiSe5 by microelectromechanical system-based tensile tests. Our findings reveal a significant in-plane anisotropic ratio (∼3.0), accounting for crystal orientation-dependent crack paths. As the thickness increases, we observe an intriguing intraplanar-to-interplanar transition of fracture along the a-axis, manifesting as stepwise crack features attributed to interlayer slippage. In contrast, ruptures along the c-axis surprisingly exhibit persistent straightness and smoothness regardless of thickness, owing to the robust interlayer shear resistance. Our work affords a promising avenue for the construction of future electronics based on nanoribbons with atomically sharp edges.
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Affiliation(s)
- Binzhao Li
- CAS Key Laboratory of Mechanical Behavior and Design of Materials, Department of Modern Mechanics, University of Science and Technology of China, Hefei 230027, China
| | - Jiahao Li
- CAS Key Laboratory of Mechanical Behavior and Design of Materials, Department of Modern Mechanics, University of Science and Technology of China, Hefei 230027, China
| | - Wei Jiang
- National Synchrotron Radiation Laboratory, Key Laboratory of Precision and Intelligent Chemistry, School of Nuclear Science and Technology, University of Science and Technology of China, Hefei 230029, China
| | - Yafei Wang
- CAS Key Laboratory of Mechanical Behavior and Design of Materials, Department of Modern Mechanics, University of Science and Technology of China, Hefei 230027, China
| | - Dong Wang
- CAS Key Laboratory of Mechanical Behavior and Design of Materials, Department of Modern Mechanics, University of Science and Technology of China, Hefei 230027, China
| | - Li Song
- National Synchrotron Radiation Laboratory, Key Laboratory of Precision and Intelligent Chemistry, School of Nuclear Science and Technology, University of Science and Technology of China, Hefei 230029, China
| | - Yinbo Zhu
- CAS Key Laboratory of Mechanical Behavior and Design of Materials, Department of Modern Mechanics, University of Science and Technology of China, Hefei 230027, China
| | - HengAn Wu
- CAS Key Laboratory of Mechanical Behavior and Design of Materials, Department of Modern Mechanics, University of Science and Technology of China, Hefei 230027, China
| | - Guorui Wang
- CAS Key Laboratory of Mechanical Behavior and Design of Materials, Department of Modern Mechanics, University of Science and Technology of China, Hefei 230027, China
- State Key Laboratory of Nonlinear Mechanics, Institute of Mechanics, Chinese Academy of Science, 15 Beisihuan West Road, Beijing 100190, China
| | - Zhong Zhang
- CAS Key Laboratory of Mechanical Behavior and Design of Materials, Department of Modern Mechanics, University of Science and Technology of China, Hefei 230027, China
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6
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Jiang Y, Mi Y, Guo J, Wang Z, Zhang N, Liu B, Luo SN. Multiple coherent amplitude modes and exciton-phonon coupling in quasi-one-dimensional excitonic insulator Ta 2NiSe 5. Phys Chem Chem Phys 2024; 26:15417-15425. [PMID: 38747307 DOI: 10.1039/d4cp00261j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/30/2024]
Abstract
An excitonic insulator (EI) is an intriguing correlated electronic phase of condensed excitons. Ta2NiSe5 is a model material for investigating condensed excitonic states. Herein, femtosecond pump-probe spectroscopy is used to study the coherent phonon dynamics and associated exciton-phonon coupling in single-crystal Ta2NiSe5. The reflectivity time series consists of exponential decay due to hot carriers and damped oscillations due to the Ag phonon vibration. Given the in-plane anisotropic thermal conductivity of Ta2NiSe5, coherent phonon oscillations are stronger with perpendicular polarization to its quasi-one-dimensional chains. The 1-, 2-, and 4-THz vibration modes show coherent amplitude responses in the EI phase of Ta2NiSe5 with increasing temperature, totally different from those of normal coherent phonons (the 3- and 3.7-THz modes). The amplitude modes at higher frequencies decouple with the EI order parameter at lower temperatures, as supported by theoretical analysis with a model Hamiltonian of the exciton-phonon coupling system. Our work provides valuable insights into the character of the EI order parameter and its coupling to multiple coherent amplitude modes.
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Affiliation(s)
- Yaohua Jiang
- Key Laboratory of Advanced Technologies of Materials, Ministry of Education, School of Materials Science and Engineering, Southwest Jiaotong University, Chengdu, Sichuan 610031, People's Republic of China.
| | - Yang Mi
- Key Laboratory of Advanced Technologies of Materials, Ministry of Education, School of Materials Science and Engineering, Southwest Jiaotong University, Chengdu, Sichuan 610031, People's Republic of China.
| | - Jia Guo
- Research Center for Life Sciences Computing, Zhejiang Lab, Hangzhou, Zhejiang 311100, People's Republic of China.
| | - Zixuan Wang
- Research Center for Life Sciences Computing, Zhejiang Lab, Hangzhou, Zhejiang 311100, People's Republic of China.
| | - Ning Zhang
- Research Center for Life Sciences Computing, Zhejiang Lab, Hangzhou, Zhejiang 311100, People's Republic of China.
| | - Bo Liu
- Research Center for Novel Computing Sensing and Intelligent Processing, Zhejiang Lab, Hangzhou, Zhejiang 311100, People's Republic of China
| | - Sheng-Nian Luo
- Key Laboratory of Advanced Technologies of Materials, Ministry of Education, School of Materials Science and Engineering, Southwest Jiaotong University, Chengdu, Sichuan 610031, People's Republic of China.
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7
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Lv BQ, Zong A, Wu D, Nie Z, Su Y, Choi D, Ilyas B, Fichera BT, Li J, Baldini E, Mogi M, Huang YB, Po HC, Meng S, Wang Y, Wang NL, Gedik N. Coexistence of Interacting Charge Density Waves in a Layered Semiconductor. PHYSICAL REVIEW LETTERS 2024; 132:206401. [PMID: 38829092 DOI: 10.1103/physrevlett.132.206401] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/23/2024] [Accepted: 03/22/2024] [Indexed: 06/05/2024]
Abstract
Coexisting orders are key features of strongly correlated materials and underlie many intriguing phenomena from unconventional superconductivity to topological orders. Here, we report the coexistence of two interacting charge-density-wave (CDW) orders in EuTe_{4}, a layered crystal that has drawn considerable attention owing to its anomalous thermal hysteresis and a semiconducting CDW state despite the absence of perfect Fermi surface nesting. By accessing unoccupied conduction bands with time- and angle-resolved photoemission measurements, we find that monolayers and bilayers of Te in the unit cell host different CDWs that are associated with distinct energy gaps. The two gaps display dichotomous evolutions following photoexcitation, where the larger bilayer CDW gap exhibits less renormalization and faster recovery. Surprisingly, the CDW in the Te monolayer displays an additional momentum-dependent gap renormalization that cannot be captured by density-functional theory calculations. This phenomenon is attributed to interlayer interactions between the two CDW orders, which account for the semiconducting nature of the equilibrium state. Our findings not only offer microscopic insights into the correlated ground state of EuTe_{4} but also provide a general nonequilibrium approach to understand coexisting, layer-dependent orders in a complex system.
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Affiliation(s)
- B Q Lv
- Tsung-Dao Lee Institute, Shanghai Jiao Tong University, Shanghai 200240, China
- Massachusetts Institute of Technology, Department of Physics, Cambridge, Massachusetts 02139, USA
- School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240, China
- Zhangjiang Institute for Advanced Study, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Alfred Zong
- Massachusetts Institute of Technology, Department of Physics, Cambridge, Massachusetts 02139, USA
- University of California at Berkeley, Department of Chemistry, Berkeley, California 94720, USA
| | - Dong Wu
- Beijing Academy of Quantum Information Sciences, Beijing 100913, China
| | - Zhengwei Nie
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Yifan Su
- Massachusetts Institute of Technology, Department of Physics, Cambridge, Massachusetts 02139, USA
| | - Dongsung Choi
- Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, Cambridge, Massachusetts 02139, USA
| | - Batyr Ilyas
- Massachusetts Institute of Technology, Department of Physics, Cambridge, Massachusetts 02139, USA
| | - Bryan T Fichera
- Massachusetts Institute of Technology, Department of Physics, Cambridge, Massachusetts 02139, USA
| | - Jiarui Li
- SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA
- Department of Applied Physics, Stanford University, Stanford, California 94305, USA
| | - Edoardo Baldini
- Massachusetts Institute of Technology, Department of Physics, Cambridge, Massachusetts 02139, USA
| | - Masataka Mogi
- Massachusetts Institute of Technology, Department of Physics, Cambridge, Massachusetts 02139, USA
| | - Y-B Huang
- Shanghai Synchrotron Radiation Facility, Shanghai Advanced Research Institute, Chinese Academy of Sciences, Shanghai 201204, China
| | - Hoi Chun Po
- Department of Physics, Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong, China
| | - Sheng Meng
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Yao Wang
- Department of Chemistry, Emory University, Atlanta, Georgia 30322, USA
| | - N L Wang
- Beijing Academy of Quantum Information Sciences, Beijing 100913, China
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China
| | - Nuh Gedik
- Massachusetts Institute of Technology, Department of Physics, Cambridge, Massachusetts 02139, USA
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8
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Zhu T, Liu K, Zhang Y, Meng S, He M, Zhang Y, Yan M, Dong X, Li X, Jiang M, Xu H. Gate Voltage- and Bias Voltage-Tunable Staggered-Gap to Broken-Gap Transition Based on WSe 2/Ta 2NiSe 5 Heterostructure for Multimode Optoelectronic Logic Gate. ACS NANO 2024; 18:11462-11473. [PMID: 38632853 DOI: 10.1021/acsnano.4c02923] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/19/2024]
Abstract
Two-dimensional (2D) materials with superior properties exhibit tremendous potential in developing next-generation electronic and optoelectronic devices. Integrating various functions into one device is highly expected as that endows 2D materials great promise for more Moore and more-than-Moore device applications. Here, we construct a WSe2/Ta2NiSe5 heterostructure by stacking the p-type WSe2 and the n-type narrow gap Ta2NiSe5 with the aim to achieve a multifunction optoelectronic device. Owing to the large interface potential barrier, the heterostructure device reveals a prominent diode feature with a large rectify ratio (7.6 × 104) and a low dark current (10-12 A). Especially, gate voltage- and bias voltage-tunable staggered-gap to broken-gap transition is achieved on the heterostructure device, which enables gate voltage-tunable forward and reverse rectifying features. As results, the heterostructure device exhibits superior self-powered photodetection properties, including a high detectivity of 1.08 × 1010 Jones and a fast response time of 91 μs. Additionally, the intrinsic structural anisotropy of Ta2NiSe5 endows the heterostructure device with strong polarization-sensitive photodetection and high-resolution polarization imaging. Based on these characteristics, a multimode optoelectronic logic gate is realized on the heterostructure via synergistically modulating the light on/off, polarization angle, gate voltage, and bias voltage. This work shed light on the future development of constructing high-performance multifunctional optoelectronic devices.
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Affiliation(s)
- Tao Zhu
- State Key Laboratory of Photon-Technology in Western China Energy, International Collaborative Center on Photoelectric Technology and Nano Functional Materials, Institute of Photonics & Photon Technology, School of Physics, Northwest University, Xi'an 710069, P. R. China
- Key Laboratory of Applied Surface and Colloid Chemistry of Ministry of Education, Shaanxi Key Laboratory for Advanced Energy Devices, School of Materials Science and Engineering, Shaanxi Normal University, Xi'an 710119, P. R. China
| | - Kai Liu
- State Key Laboratory of Photon-Technology in Western China Energy, International Collaborative Center on Photoelectric Technology and Nano Functional Materials, Institute of Photonics & Photon Technology, School of Physics, Northwest University, Xi'an 710069, P. R. China
- Key Laboratory of Applied Surface and Colloid Chemistry of Ministry of Education, Shaanxi Key Laboratory for Advanced Energy Devices, School of Materials Science and Engineering, Shaanxi Normal University, Xi'an 710119, P. R. China
| | - Yao Zhang
- State Key Laboratory of Photon-Technology in Western China Energy, International Collaborative Center on Photoelectric Technology and Nano Functional Materials, Institute of Photonics & Photon Technology, School of Physics, Northwest University, Xi'an 710069, P. R. China
- Key Laboratory of Applied Surface and Colloid Chemistry of Ministry of Education, Shaanxi Key Laboratory for Advanced Energy Devices, School of Materials Science and Engineering, Shaanxi Normal University, Xi'an 710119, P. R. China
| | - Si Meng
- Key Laboratory of Applied Surface and Colloid Chemistry of Ministry of Education, Shaanxi Key Laboratory for Advanced Energy Devices, School of Materials Science and Engineering, Shaanxi Normal University, Xi'an 710119, P. R. China
| | - Mengfei He
- Key Laboratory of Applied Surface and Colloid Chemistry of Ministry of Education, Shaanxi Key Laboratory for Advanced Energy Devices, School of Materials Science and Engineering, Shaanxi Normal University, Xi'an 710119, P. R. China
| | - Yingli Zhang
- State Key Laboratory of Photon-Technology in Western China Energy, International Collaborative Center on Photoelectric Technology and Nano Functional Materials, Institute of Photonics & Photon Technology, School of Physics, Northwest University, Xi'an 710069, P. R. China
| | - Minglu Yan
- State Key Laboratory of Photon-Technology in Western China Energy, International Collaborative Center on Photoelectric Technology and Nano Functional Materials, Institute of Photonics & Photon Technology, School of Physics, Northwest University, Xi'an 710069, P. R. China
| | - Xiaoxiang Dong
- Department of Physics, Xiamen University, Xiamen 361005, P. R. China
| | - Xiaobo Li
- Shaanxi Joint Key Laboratory of Graphene, School of Advanced Materials and Nanotechnology, Xidian University, Xi'an 710126, P. R. China
| | - Man Jiang
- State Key Laboratory of Photon-Technology in Western China Energy, International Collaborative Center on Photoelectric Technology and Nano Functional Materials, Institute of Photonics & Photon Technology, School of Physics, Northwest University, Xi'an 710069, P. R. China
| | - Hua Xu
- Key Laboratory of Applied Surface and Colloid Chemistry of Ministry of Education, Shaanxi Key Laboratory for Advanced Energy Devices, School of Materials Science and Engineering, Shaanxi Normal University, Xi'an 710119, P. R. China
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Michael MH, Haque SRU, Windgaetter L, Latini S, Zhang Y, Rubio A, Averitt RD, Demler E. Photonic time-crystalline behaviour mediated by phonon squeezing in Ta 2NiSe 5. Nat Commun 2024; 15:3638. [PMID: 38684735 PMCID: PMC11059354 DOI: 10.1038/s41467-024-47855-8] [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: 09/23/2023] [Accepted: 04/11/2024] [Indexed: 05/02/2024] Open
Abstract
Photonic time crystals refer to materials whose dielectric properties are periodic in time, analogous to a photonic crystal whose dielectric properties is periodic in space. Here, we theoretically investigate photonic time-crystalline behaviour initiated by optical excitation above the electronic gap of the excitonic insulator candidate Ta2NiSe5. We show that after electron photoexcitation, electron-phonon coupling leads to an unconventional squeezed phonon state, characterised by periodic oscillations of phonon fluctuations. Squeezing oscillations lead to photonic time crystalline behaviour. The key signature of the photonic time crystalline behaviour is terahertz (THz) amplification of reflectivity in a narrow frequency band. The theory is supported by experimental results on Ta2NiSe5 where photoexcitation with short pulses leads to enhanced THz reflectivity with the predicted features. We explain the key mechanism leading to THz amplification in terms of a simplified electron-phonon Hamiltonian motivated by ab-initio DFT calculations. Our theory suggests that the pumped Ta2NiSe5 is a gain medium, demonstrating that squeezed phonon noise may be used to create THz amplifiers in THz communication applications.
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Affiliation(s)
- Marios H Michael
- Department of Physics, Harvard University, Cambridge, MA, 02138, USA.
- Max Planck Institute for the Structure and Dynamics of Matter, Luruper Chausse 149, 22761, Hamburg, Germany.
| | - Sheikh Rubaiat Ul Haque
- Department of Physics, University of California San Diego, La Jolla, CA, 92093, USA.
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, CA, 94025, USA.
| | - Lukas Windgaetter
- Max Planck Institute for the Structure and Dynamics of Matter, Luruper Chausse 149, 22761, Hamburg, Germany
| | - Simone Latini
- Max Planck Institute for the Structure and Dynamics of Matter, Luruper Chausse 149, 22761, Hamburg, Germany
| | - Yuan Zhang
- Department of Physics, University of California San Diego, La Jolla, CA, 92093, USA
| | - Angel Rubio
- Max Planck Institute for the Structure and Dynamics of Matter, Luruper Chausse 149, 22761, Hamburg, Germany
- Center for Computational Quantum Physics, The Flatiron Institute, 162 Fifth Avenue, New York, 10010, NY, USA
| | - Richard D Averitt
- Department of Physics, University of California San Diego, La Jolla, CA, 92093, USA
| | - Eugene Demler
- Department of Physics, Harvard University, Cambridge, MA, 02138, USA
- Institute for Theoretical Physics, ETH Zürich, 8093, Zürich, Switzerland
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10
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Ma Y, Du Y, Wu W, Shi Z, Meng X, Yuan X. Synthesis and Characterization of 2D Ternary Compound TMD Materials Ta 3VSe 8. MICROMACHINES 2024; 15:591. [PMID: 38793164 PMCID: PMC11123142 DOI: 10.3390/mi15050591] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/06/2024] [Revised: 04/24/2024] [Accepted: 04/25/2024] [Indexed: 05/26/2024]
Abstract
Two-dimensional (2D) transition metal dichalcogenides (TMDs) are garnering considerable scientific interest, prompting discussion regarding their prospective applications in the fields of nanoelectronics and spintronics while also fueling groundbreaking discoveries in phenomena such as the fractional quantum anomalous Hall effect (FQAHE) and exciton dynamics. The abundance of binary compound TMDs, such as MX2 (M = Mo, W; X = S, Se, Te), has unlocked myriad avenues of exploration. However, the exploration of ternary compound TMDs remains relatively limited, with notable examples being Ta2NiS5 and Ta2NiSe5. In this study, we report the synthesis of a new 2D ternary compound TMD materials, Ta3VSe8, employing the chemical vapor transport (CVT) method. The as-grown bulk crystal is shiny and can be easily exfoliated. The crystal quality and structure are verified by X-ray diffraction (XRD), while the surface morphology, stoichiometric ratio, and uniformity are determined by scanning electron microscopy (SEM). Although the phonon property is found stable at different temperatures, magneto-resistivity evolves. These findings provide a possible approach for the realization and exploration of ternary compound TMDs.
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Affiliation(s)
- Yuanji Ma
- State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200241, China
| | - Yuhan Du
- State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200241, China
| | - Wenbin Wu
- State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200241, China
| | - Zeping Shi
- State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200241, China
| | - Xianghao Meng
- State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200241, China
| | - Xiang Yuan
- State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200241, China
- Shanghai Center of Brain-Inspired Intelligent Materials and Devices, Department of Electronics, East China Normal University, Shanghai 200241, China
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11
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Guan M, Chen D, Chen Q, Yao Y, Meng S. Coherent Phonon Assisted Ultrafast Order-Parameter Reversal and Hidden Metallic State in Ta_{2}NiSe_{5}. PHYSICAL REVIEW LETTERS 2023; 131:256503. [PMID: 38181365 DOI: 10.1103/physrevlett.131.256503] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/22/2023] [Revised: 11/20/2023] [Accepted: 12/01/2023] [Indexed: 01/07/2024]
Abstract
The nonequilibrium dynamics during photoinduced insulator-to-metal transition (IMT) in the excitonic insulator (EI) candidate Ta_{2}NiSe_{5} have been investigated, which reproduce the timescale and spectral features of the ultrafast switch and reveal intricate many-body interactions involving multidegrees of freedom. The key role of lattice order parameter (OP) reversal, occurring on a timescale comparable to that of purely electronic processes (<100 fs), is identified. This reversal is enabled by the anharmonic interactions between EI-OP-coupled phonons and the conventional coherent phonons, leading to a modified potential energy landscape and a high-frequency mode up-conversion. The phonon excitation depends on the dynamics of photocarriers distributed around the Fermi level, and thus intertwines with the excitonic quenching and the complete gap collapse. These findings provide a comprehensive understanding of exciton-phonon dynamics in correlated quantum materials.
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Affiliation(s)
- Mengxue Guan
- Centre for Quantum Physics, Key Laboratory of Advanced Optoelectronic Quantum Architecture and Measurement (Ministry of Education), School of Physics, Beijing Institute of Technology, Beijing 100081, China
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Daqiang Chen
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100190, China
| | - Qing Chen
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100190, China
| | - Yugui Yao
- Centre for Quantum Physics, Key Laboratory of Advanced Optoelectronic Quantum Architecture and Measurement (Ministry of Education), School of Physics, Beijing Institute of Technology, Beijing 100081, China
| | - Sheng Meng
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100190, China
- Songshan Lake Materials Laboratory, Dongguan, Guangdong 523808, China
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12
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Chen C, Tang W, Chen X, Kang Z, Ding S, Scott K, Wang S, Li Z, Ruff JPC, Hashimoto M, Lu DH, Jozwiak C, Bostwick A, Rotenberg E, da Silva Neto EH, Birgeneau RJ, Chen Y, Louie SG, Wang Y, He Y. Anomalous excitonic phase diagram in band-gap-tuned Ta 2Ni(Se,S) 5. Nat Commun 2023; 14:7512. [PMID: 37980419 PMCID: PMC10657405 DOI: 10.1038/s41467-023-43365-1] [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: 06/01/2023] [Accepted: 11/07/2023] [Indexed: 11/20/2023] Open
Abstract
During a band-gap-tuned semimetal-to-semiconductor transition, Coulomb attraction between electrons and holes can cause spontaneously formed excitons near the zero-band-gap point, or the Lifshitz transition point. This has become an important route to realize bulk excitonic insulators - an insulating ground state distinct from single-particle band insulators. How this route manifests from weak to strong coupling is not clear. In this work, using angle-resolved photoemission spectroscopy (ARPES) and high-resolution synchrotron x-ray diffraction (XRD), we investigate the broken symmetry state across the semimetal-to-semiconductor transition in a leading bulk excitonic insulator candidate system Ta2Ni(Se,S)5. A broken symmetry phase is found to be continuously suppressed from the semimetal side to the semiconductor side, contradicting the anticipated maximal excitonic instability around the Lifshitz transition. Bolstered by first-principles and model calculations, we find strong interband electron-phonon coupling to play a crucial role in the enhanced symmetry breaking on the semimetal side of the phase diagram. Our results not only provide insight into the longstanding debate of the nature of intertwined orders in Ta2NiSe5, but also establish a basis for exploring band-gap-tuned structural and electronic instabilities in strongly coupled systems.
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Affiliation(s)
- Cheng Chen
- Department of Physics, University of Oxford, Oxford, OX1 3PU, United Kingdom
- Department of Applied Physics, Yale University, New Haven, CT, 06511, USA
| | - Weichen Tang
- Physics Department, University of California, Berkeley, CA, 94720, USA
- Materials Sciences Division, Lawrence Berkeley National Lab, Berkeley, CA, 94720, USA
| | - Xiang Chen
- Physics Department, University of California, Berkeley, CA, 94720, USA
- Materials Sciences Division, Lawrence Berkeley National Lab, Berkeley, CA, 94720, USA
| | - Zhibo Kang
- Department of Applied Physics, Yale University, New Haven, CT, 06511, USA
| | - Shuhan Ding
- Department of Physics and Astronomy, Clemson University, Clemson, SC, 29631, USA
| | - Kirsty Scott
- Department of Physics, Yale University, New Haven, CT, 06511, USA
| | - Siqi Wang
- Department of Applied Physics, Yale University, New Haven, CT, 06511, USA
| | - Zhenglu Li
- Physics Department, University of California, Berkeley, CA, 94720, USA
- Materials Sciences Division, Lawrence Berkeley National Lab, Berkeley, CA, 94720, USA
- Mork Family Department of Chemical Engineering and Materials Science, University of Southern California, Los Angeles, CA, 90089, USA
| | - Jacob P C Ruff
- Cornell High Energy Synchrotron Source, Cornell University, Ithaca, NY, 14853, USA
| | - Makoto Hashimoto
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, CA, 94025, USA
| | - Dong-Hui Lu
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, CA, 94025, USA
| | - Chris Jozwiak
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA
| | - Aaron Bostwick
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA
| | - Eli Rotenberg
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA
| | | | - Robert J Birgeneau
- Physics Department, University of California, Berkeley, CA, 94720, USA
- Materials Sciences Division, Lawrence Berkeley National Lab, Berkeley, CA, 94720, USA
- Department of Materials Science and Engineering, University of California, Berkeley, CA, 94720, USA
| | - Yulin Chen
- Department of Physics, University of Oxford, Oxford, OX1 3PU, United Kingdom
| | - Steven G Louie
- Physics Department, University of California, Berkeley, CA, 94720, USA.
- Materials Sciences Division, Lawrence Berkeley National Lab, Berkeley, CA, 94720, USA.
| | - Yao Wang
- Department of Physics and Astronomy, Clemson University, Clemson, SC, 29631, USA.
- Department of Chemistry, Emory University, Atlanta, GA, 30322, USA.
| | - Yu He
- Department of Applied Physics, Yale University, New Haven, CT, 06511, USA.
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13
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Hyde PA, Cen J, Cassidy SJ, Rees NH, Holdship P, Smith RI, Zhu B, Scanlon DO, Clarke SJ. Lithium Intercalation into the Excitonic Insulator Candidate Ta 2NiSe 5. Inorg Chem 2023. [PMID: 37466301 PMCID: PMC10394660 DOI: 10.1021/acs.inorgchem.3c01510] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/20/2023]
Abstract
A new reduced phase derived from the excitonic insulator candidate Ta2NiSe5 has been synthesized via the intercalation of lithium. LiTa2NiSe5 crystallizes in the orthorhombic space group Pmnb (no. 62) with lattice parameters a = 3.50247(3) Å, b = 13.4053(4) Å, c = 15.7396(2) Å, and Z = 4, with an increase of the unit cell volume by 5.44(1)% compared with Ta2NiSe5. Significant rearrangement of the Ta-Ni-Se layers is observed, in particular a very significant relative displacement of the layers compared to the parent phase, similar to that which occurs under hydrostatic pressure. Neutron powder diffraction experiments and computational analysis confirm that Li occupies a distorted triangular prismatic site formed by Se atoms of adjacent Ta2NiSe5 layers with an average Li-Se bond length of 2.724(2) Å. Li-NMR experiments show a single Li environment at ambient temperature. Intercalation suppresses the distortion to monoclinic symmetry that occurs in Ta2NiSe5 at 328 K and that is believed to be driven by the formation of an excitonic insulating state. Magnetometry data show that the reduced phase has a smaller net diamagnetic susceptibility than Ta2NiSe5 due to the enhancement of the temperature-independent Pauli paramagnetism caused by the increased density of states at the Fermi level evident also from the calculations, consistent with the injection of electrons during intercalation and formation of a metallic phase.
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Affiliation(s)
- P A Hyde
- Department of Chemistry, Inorganic Chemistry Laboratory, University of Oxford, South Parks Road, Oxford OX1 3QR, U.K
| | - J Cen
- Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, U.K
- Thomas Young Centre, University College London, Gower Street, London WC1E 6BT, U.K
| | - S J Cassidy
- Department of Chemistry, Inorganic Chemistry Laboratory, University of Oxford, South Parks Road, Oxford OX1 3QR, U.K
| | - N H Rees
- Department of Chemistry, Inorganic Chemistry Laboratory, University of Oxford, South Parks Road, Oxford OX1 3QR, U.K
| | - P Holdship
- Department of Earth Sciences, University of Oxford, South Parks Road, Oxford OX1 3AN, U.K
| | - R I Smith
- Rutherford Appleton Laboratory, ISIS Facility, Harwell Campus, Didcot, Oxon OX11 0QX, U.K
| | - B Zhu
- Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, U.K
- Thomas Young Centre, University College London, Gower Street, London WC1E 6BT, U.K
| | - D O Scanlon
- Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, U.K
- Thomas Young Centre, University College London, Gower Street, London WC1E 6BT, U.K
| | - S J Clarke
- Department of Chemistry, Inorganic Chemistry Laboratory, University of Oxford, South Parks Road, Oxford OX1 3QR, U.K
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