1
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Shibuta M, Nakajima A. Imaging of ultrafast photoexcited electron dynamics in pentacene nanocrystals on a graphite substrate. NANOSCALE 2024; 16:12397-12405. [PMID: 38832543 DOI: 10.1039/d4nr00720d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2024]
Abstract
Understanding molecular film growth on substrates and the ultrafast electron dynamics at their interface is crucial for advancing next-generation organic electronics. We have focused on studying the ultrafast photoexcited electron dynamics in nanoscale organic crystals of an aromatic molecule, pentacene, on a two-dimensional material of graphite substrate. Through the use of time-resolved two-photon photoelectron emission microscopy (2P-PEEM), we have visualized the ultrafast lateral evolution of photoexcited electrons. By resonantly tuning the incident photon to excite pentacene molecules, polarization-dependent 2P-PEEM has revealed that pentacene nanocrystals (sub- to several μm) on the substrate exhibit a preferential orientation, in which a molecular π-orbital contacts the substrate in a "lying flat" orientation, facilitating electron transfer to the substrate. The time-resolved 2P-PEEM captures the motion of excited electrons in a femto- to pico-second timescale, clearly imaging the ultrafast charge transfer and lateral expansion two-dimensionally on the graphite substrate. Moreover, we found that the lying-flat molecular orientation of pentacene nanocrystals is transformable into a "standing-up" one through gentle heating up to 50 °C. These experimental insights using time-resolved 2P-PEEM will be highly valuable in enhancing the photofunctionalities of organic electronic devices by controlled molecular deposition.
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Affiliation(s)
- Masahiro Shibuta
- Keio Institute of Pure and Applied Sciences (KiPAS), Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama 223-8522, Japan.
| | - Atsushi Nakajima
- Keio Institute of Pure and Applied Sciences (KiPAS), Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama 223-8522, Japan.
- Department of Chemistry, Faculty of Science and Technology, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama 223-8522, Japan
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2
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Sun X, Williams J, Sharma S, Kunjir S, Morris D, Zhao S, Ruan CY. Precision-controlled ultrafast electron microscope platforms. A case study: Multiple-order coherent phonon dynamics in 1T-TaSe 2 probed at 50 fs-10 fm scales. STRUCTURAL DYNAMICS (MELVILLE, N.Y.) 2024; 11:024305. [PMID: 38566810 PMCID: PMC10987196 DOI: 10.1063/4.0000242] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/01/2024] [Accepted: 03/08/2024] [Indexed: 04/04/2024]
Abstract
We report on the first detailed beam tests attesting the fundamental principle behind the development of high-current-efficiency ultrafast electron microscope systems where a radio frequency (RF) cavity is incorporated as a condenser lens in the beam delivery system. To allow for the experiment to be carried out with a sufficient resolution to probe the performance at the emittance floor, a new cascade loop RF controller system is developed to reduce the RF noise floor. Temporal resolution at 50 fs in full-width-at-half-maximum and detection sensitivity better than 1% are demonstrated on exfoliated 1T-TaSe2 system under a moderate repetition rate. To benchmark the performance, multi-terahertz edge-mode coherent phonon excitation is employed as the standard candle. The high temporal resolution and the significant visibility to very low dynamical contrast in diffraction signals via high-precision phase-space manipulation give strong support to the working principle for the new high-brightness femtosecond electron microscope systems.
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Affiliation(s)
- Xiaoyi Sun
- Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan 48824, USA
| | - Joseph Williams
- Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan 48824, USA
| | - Sachin Sharma
- Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan 48824, USA
| | - Shriraj Kunjir
- Facility for Rare Isotope Beams, Michigan State University, East Lansing, Michigan 48824, USA
| | - Dan Morris
- Facility for Rare Isotope Beams, Michigan State University, East Lansing, Michigan 48824, USA
| | - Shen Zhao
- Facility for Rare Isotope Beams, Michigan State University, East Lansing, Michigan 48824, USA
| | - Chong-Yu Ruan
- Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan 48824, USA
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3
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Othman MAK, Gabriel AE, Snively EC, Kozina ME, Shen X, Ji F, Lewis S, Weathersby S, Vasireddy P, Luo D, Wang X, Hoffmann MC, Nanni EA. Improved temporal resolution in ultrafast electron diffraction measurements through THz compression and time-stamping. STRUCTURAL DYNAMICS (MELVILLE, N.Y.) 2024; 11:024311. [PMID: 38655563 PMCID: PMC11037933 DOI: 10.1063/4.0000230] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/19/2023] [Accepted: 04/05/2024] [Indexed: 04/26/2024]
Abstract
We present an experimental demonstration of ultrafast electron diffraction (UED) with THz-driven electron bunch compression and time-stamping that enables UED probes with improved temporal resolution. Through THz-driven longitudinal bunch compression, a compression factor of approximately four is achieved. Moreover, the time-of-arrival jitter between the compressed electron bunch and a pump laser pulse is suppressed by a factor of three. Simultaneously, the THz interaction imparts a transverse spatiotemporal correlation on the electron distribution, which we utilize to further enhance the precision of time-resolved UED measurements. We use this technique to probe single-crystal gold nanofilms and reveal transient oscillations in the THz near fields with a temporal resolution down to 50 fs. These oscillations were previously beyond reach in the absence of THz compression and time-stamping.
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Affiliation(s)
- Mohamed A. K. Othman
- SLAC National Accelerator Laboratory, Stanford University, Menlo Park, California 94025, USA
| | - Annika E. Gabriel
- SLAC National Accelerator Laboratory, Stanford University, Menlo Park, California 94025, USA
| | - Emma C. Snively
- SLAC National Accelerator Laboratory, Stanford University, Menlo Park, California 94025, USA
| | - Michael E. Kozina
- SLAC National Accelerator Laboratory, Stanford University, Menlo Park, California 94025, USA
| | - Xiaozhe Shen
- SLAC National Accelerator Laboratory, Stanford University, Menlo Park, California 94025, USA
| | - Fuhao Ji
- SLAC National Accelerator Laboratory, Stanford University, Menlo Park, California 94025, USA
| | - Samantha Lewis
- SLAC National Accelerator Laboratory, Stanford University, Menlo Park, California 94025, USA
| | - Stephen Weathersby
- SLAC National Accelerator Laboratory, Stanford University, Menlo Park, California 94025, USA
| | - Praful Vasireddy
- SLAC National Accelerator Laboratory, Stanford University, Menlo Park, California 94025, USA
| | - Duan Luo
- SLAC National Accelerator Laboratory, Stanford University, Menlo Park, California 94025, USA
| | - Xijie Wang
- SLAC National Accelerator Laboratory, Stanford University, Menlo Park, California 94025, USA
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4
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Zhang Y, Murthy C, Kafle TR, You W, Shi X, Min L, Wang HH, Li N, Gopalan V, Mao Z, Rossnagel K, Yang L, Kapteyn H, Nandkishore R, Murnane M. Bipolaronic Nature of the Pseudogap in Quasi-One-Dimensional (TaSe 4) 2I Revealed via Weak Photoexcitation. NANO LETTERS 2023; 23:8392-8398. [PMID: 37682637 DOI: 10.1021/acs.nanolett.3c01078] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/10/2023]
Abstract
The origin of the pseudogap in many strongly correlated materials has been a longstanding puzzle. Here, we present experimental evidence that many-body interactions among small Holstein polarons, i.e., the formation of bipolarons, are primarily responsible for the pseudogap in (TaSe4)2I. After weak photoexcitation of the material, we observe the appearance of both dispersive (single-particle bare band) and flat bands (single-polaron sub-bands) in the gap by using time- and angle-resolved photoemission spectroscopy. Based on Monte Carlo simulations of the Holstein model, we propose that the melting of pseudogap and emergence of new bands originate from a bipolaron to single-polaron crossover. We also observe dramatically different relaxation times for the excited in-gap states in (TaSe4)2I (∼600 fs) compared with another 1D material Rb0.3MoO3 (∼60 fs), which provides a new method for distinguishing between pseudogaps induced by polaronic or Luttinger-liquid many-body interactions.
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Affiliation(s)
- Yingchao Zhang
- Department of Physics and JILA, University of Colorado and NIST, Boulder, Colorado 80309, United States
| | - Chaitanya Murthy
- Department of Physics, Stanford University, Stanford, California 94305, United States
| | - Tika R Kafle
- Department of Physics and JILA, University of Colorado and NIST, Boulder, Colorado 80309, United States
| | - Wenjing You
- Department of Physics and JILA, University of Colorado and NIST, Boulder, Colorado 80309, United States
| | - Xun Shi
- Department of Physics and JILA, University of Colorado and NIST, Boulder, Colorado 80309, United States
| | - Lujin Min
- Materials Research Institute and Department of Materials Science & Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Huaiyu Hugo Wang
- Materials Research Institute and Department of Materials Science & Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Na Li
- Department of Physics and JILA, University of Colorado and NIST, Boulder, Colorado 80309, United States
| | - Venkatraman Gopalan
- Materials Research Institute and Department of Materials Science & Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Zhiqiang Mao
- Materials Research Institute and Department of Materials Science & Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
- Department of Physics, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Kai Rossnagel
- Institute of Experimental and Applied Physics, Kiel University, D-24098 Kiel, Germany
- Ruprecht Haensel Laboratory, Deutsches Elektronen-Synchrotron DESY, D-22607 Hamburg, Germany
| | - Lexian Yang
- State Key Laboratory of Low Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China
- Frontier Science Center for Quantum Information, Beijing 100084, China
| | - Henry Kapteyn
- Department of Physics and JILA, University of Colorado and NIST, Boulder, Colorado 80309, United States
- KMLabs Inc., Boulder, Colorado 80301, United States
| | - Rahul Nandkishore
- Department of Physics and Center for Theory of Quantum Matter, University of Colorado Boulder, Boulder, Colorado 80309, United States
| | - Margaret Murnane
- Department of Physics and JILA, University of Colorado and NIST, Boulder, Colorado 80309, United States
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5
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Nguyen QLD, Simoni J, Dorney KM, Shi X, Ellis JL, Brooks NJ, Hickstein DD, Grennell AG, Yazdi S, Campbell EEB, Tan LZ, Prendergast D, Daligault J, Kapteyn HC, Murnane MM. Direct Observation of Enhanced Electron-Phonon Coupling in Copper Nanoparticles in the Warm-Dense Matter Regime. PHYSICAL REVIEW LETTERS 2023; 131:085101. [PMID: 37683150 DOI: 10.1103/physrevlett.131.085101] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/20/2021] [Revised: 06/27/2022] [Accepted: 05/26/2023] [Indexed: 09/10/2023]
Abstract
Warm dense matter (WDM) represents a highly excited state that lies at the intersection of solids, plasmas, and liquids and that cannot be described by equilibrium theories. The transient nature of this state when created in a laboratory, as well as the difficulties in probing the strongly coupled interactions between the electrons and the ions, make it challenging to develop a complete understanding of matter in this regime. In this work, by exciting isolated ∼8 nm copper nanoparticles with a femtosecond laser below the ablation threshold, we create uniformly excited WDM. Using photoelectron spectroscopy, we measure the instantaneous electron temperature and extract the electron-ion coupling of the nanoparticle as it undergoes a solid-to-WDM phase transition. By comparing with state-of-the-art theories, we confirm that the superheated nanoparticles lie at the boundary between hot solids and plasmas, with associated strong electron-ion coupling. This is evidenced both by a fast energy loss of electrons to ions, and a strong modulation of the electron temperature induced by strong acoustic breathing modes that change the nanoparticle volume. This work demonstrates a new route for experimental exploration of the exotic properties of WDM.
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Affiliation(s)
- Quynh L D Nguyen
- JILA, Department of Physics, University of Colorado and NIST, Boulder, Colorado 80309, USA
| | - Jacopo Simoni
- Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
- Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - Kevin M Dorney
- JILA, Department of Physics, University of Colorado and NIST, Boulder, Colorado 80309, USA
| | - Xun Shi
- JILA, Department of Physics, University of Colorado and NIST, Boulder, Colorado 80309, USA
| | - Jennifer L Ellis
- JILA, Department of Physics, University of Colorado and NIST, Boulder, Colorado 80309, USA
| | - Nathan J Brooks
- JILA, Department of Physics, University of Colorado and NIST, Boulder, Colorado 80309, USA
| | - Daniel D Hickstein
- Kapteyn-Murnane Laboratories Inc., 4775 Walnut St #102, Boulder, Colorado 80301, USA
| | - Amanda G Grennell
- Department of Chemistry, University of Colorado Boulder, Boulder, Colorado 80309 80309, USA
| | - Sadegh Yazdi
- Renewable and Sustainable Energy Institute, University of Colorado Boulder, Boulder, Colorado 80309, USA
| | - Eleanor E B Campbell
- EaStCHEM, School of Chemistry, Edinburgh University, David Brewster Road, Edinburgh EH9 3FJ, United Kingdom
- Department of Physics, Ewha Womans University, Seoul 03760, Republic of Korea
| | - Liang Z Tan
- Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - David Prendergast
- Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - Jerome Daligault
- Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
| | - Henry C Kapteyn
- JILA, Department of Physics, University of Colorado and NIST, Boulder, Colorado 80309, USA
- Kapteyn-Murnane Laboratories Inc., 4775 Walnut St #102, Boulder, Colorado 80301, USA
| | - Margaret M Murnane
- JILA, Department of Physics, University of Colorado and NIST, Boulder, Colorado 80309, USA
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6
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Duan S, Xia W, Huang C, Wang S, Gu L, Liu H, Xiang D, Qian D, Guo Y, Zhang W. Ultrafast Switching from the Charge Density Wave Phase to a Metastable Metallic State in 1T-TiSe_{2}. PHYSICAL REVIEW LETTERS 2023; 130:226501. [PMID: 37327423 DOI: 10.1103/physrevlett.130.226501] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/20/2023] [Revised: 03/28/2023] [Accepted: 05/04/2023] [Indexed: 06/18/2023]
Abstract
The ultrafast electronic structures of the charge density wave material 1T-TiSe_{2} were investigated by high-resolution time- and angle-resolved photoemission spectroscopy. We found that the quasiparticle populations drove ultrafast electronic phase transitions in 1T-TiSe_{2} within 100 fs after photoexcitation, and a metastable metallic state, which was significantly different from the equilibrium normal phase, was evidenced far below the charge density wave transition temperature. Detailed time- and pump-fluence-dependent experiments revealed that the photoinduced metastable metallic state was a result of the halted motion of the atoms through the coherent electron-phonon coupling process, and the lifetime of this state was prolonged to picoseconds with the highest pump fluence used in this study. Ultrafast electronic dynamics were well captured by the time-dependent Ginzburg-Landau model. Our work demonstrates a mechanism for realizing novel electronic states by photoinducing coherent motion of atoms in the lattice.
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Affiliation(s)
- Shaofeng Duan
- Key Laboratory of Artificial Structures and Quantum Control (Ministry of Education), School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Wei Xia
- School of Physical Science and Technology, ShanghaiTech University, Shanghai 201210, China
| | - Chaozhi Huang
- Key Laboratory of Artificial Structures and Quantum Control (Ministry of Education), School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Shichong Wang
- Key Laboratory of Artificial Structures and Quantum Control (Ministry of Education), School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Lingxiao Gu
- Key Laboratory of Artificial Structures and Quantum Control (Ministry of Education), School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Haoran Liu
- Key Laboratory of Artificial Structures and Quantum Control (Ministry of Education), School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Dao Xiang
- Key Laboratory for Laser Plasmas (Ministry of Education), School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240, China
- Tsung-Dao Lee Institute, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Dong Qian
- Key Laboratory of Artificial Structures and Quantum Control (Ministry of Education), School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240, China
- Tsung-Dao Lee Institute, Shanghai Jiao Tong University, Shanghai 200240, China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
| | - Yanfeng Guo
- School of Physical Science and Technology, ShanghaiTech University, Shanghai 201210, China
| | - Wentao Zhang
- Key Laboratory of Artificial Structures and Quantum Control (Ministry of Education), School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240, China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
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7
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Sayers CJ, Cerullo G, Zhang Y, Sanders CE, Chapman RT, Wyatt AS, Chatterjee G, Springate E, Wolverson D, Da Como E, Carpene E. Exploring the Charge Density Wave Phase of 1T-TaSe_{2}: Mott or Charge-Transfer Gap? PHYSICAL REVIEW LETTERS 2023; 130:156401. [PMID: 37115877 DOI: 10.1103/physrevlett.130.156401] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/10/2022] [Revised: 12/29/2022] [Accepted: 03/02/2023] [Indexed: 06/19/2023]
Abstract
1T-TaSe_{2} is widely believed to host a Mott metal-insulator transition in the charge density wave (CDW) phase according to the spectroscopic observation of a band gap that extends across all momentum space. Previous investigations inferred that the occurrence of the Mott phase is limited to the surface only of bulk specimens, but recent analysis on thin samples revealed that the Mott-like behavior, observed in the monolayer, is rapidly suppressed with increasing thickness. Here, we report combined time- and angle-resolved photoemission spectroscopy and theoretical investigations of the electronic structure of 1T-TaSe_{2}. Our experimental results confirm the existence of a state above E_{F}, previously ascribed to the upper Hubbard band, and an overall band gap of ∼0.7 eV at Γ[over ¯]. However, supported by density functional theory calculations, we demonstrate that the origin of this state and the gap rests on band structure modifications induced by the CDW phase alone, without the need for Mott correlation effects.
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Affiliation(s)
- C J Sayers
- Dipartimento di Fisica, Politecnico di Milano, Milan 20133, Italy
| | - G Cerullo
- Dipartimento di Fisica, Politecnico di Milano, Milan 20133, Italy
| | - Y Zhang
- STFC Central Laser Facility, Research Complex at Harwell, Harwell Campus, Didcot OX11 0QX, United Kingdom
| | - C E Sanders
- STFC Central Laser Facility, Research Complex at Harwell, Harwell Campus, Didcot OX11 0QX, United Kingdom
| | - R T Chapman
- STFC Central Laser Facility, Research Complex at Harwell, Harwell Campus, Didcot OX11 0QX, United Kingdom
| | - A S Wyatt
- STFC Central Laser Facility, Research Complex at Harwell, Harwell Campus, Didcot OX11 0QX, United Kingdom
| | - G Chatterjee
- STFC Central Laser Facility, Research Complex at Harwell, Harwell Campus, Didcot OX11 0QX, United Kingdom
| | - E Springate
- STFC Central Laser Facility, Research Complex at Harwell, Harwell Campus, Didcot OX11 0QX, United Kingdom
| | - D Wolverson
- Centre for Nanoscience and Nanotechnology, Department of Physics, University of Bath, Bath BA2 7AY, United Kingdom
| | - E Da Como
- Centre for Nanoscience and Nanotechnology, Department of Physics, University of Bath, Bath BA2 7AY, United Kingdom
| | - E Carpene
- IFN-CNR, Dipartimento di Fisica, Politecnico di Milano, Milan 20133, Italy
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8
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Gentry C, Liao CT, You W, Ryan SA, Varner BA, Shi X, Guan MX, Gray T, Temple D, Meng S, Raschke M, Rossnagel K, Kapteyn HC, Murnane MM, Cating-Subramanian E. Super-resolved time–frequency measurements of coupled phonon dynamics in a 2D quantum material. Sci Rep 2022; 12:19734. [DOI: 10.1038/s41598-022-22055-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2021] [Accepted: 10/10/2022] [Indexed: 11/18/2022] Open
Abstract
AbstractMethods to probe and understand the dynamic response of materials following impulsive excitation are important for many fields, from materials and energy sciences to chemical and neuroscience. To design more efficient nano, energy, and quantum devices, new methods are needed to uncover the dominant excitations and reaction pathways. In this work, we implement a newly-developed superlet transform—a super-resolution time-frequency analytical method—to analyze and extract phonon dynamics in a laser-excited two-dimensional (2D) quantum material. This quasi-2D system, 1T-TaSe2, supports both equilibrium and metastable light-induced charge density wave (CDW) phases mediated by strongly coupled phonons. We compare the effectiveness of the superlet transform to standard time-frequency techniques. We find that the superlet transform is superior in both time and frequency resolution, and use it to observe and validate novel physics. In particular, we show fluence-dependent changes in the coupled dynamics of three phonon modes that are similar in frequency, including the CDW amplitude mode, that clearly demonstrate a change in the dominant charge-phonon couplings. More interestingly, the frequencies of the three phonon modes, including the strongly-coupled CDW amplitude mode, remain time- and fluence-independent, which is unusual compared to previously investigated materials. Our study opens a new avenue for capturing the coherent evolution and couplings of strongly-coupled materials and quantum systems.
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9
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Gao FY, Zhang Z, Sun Z, Ye L, Cheng YH, Liu ZJ, Checkelsky JG, Baldini E, Nelson KA. Snapshots of a light-induced metastable hidden phase driven by the collapse of charge order. SCIENCE ADVANCES 2022; 8:eabp9076. [PMID: 35867789 PMCID: PMC9307249 DOI: 10.1126/sciadv.abp9076] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/06/2022] [Accepted: 06/09/2022] [Indexed: 06/15/2023]
Abstract
Nonequilibrium hidden states provide a unique window into thermally inaccessible regimes of strong coupling between microscopic degrees of freedom in quantum materials. Understanding the origin of these states allows the exploration of far-from-equilibrium thermodynamics and the development of optoelectronic devices with on-demand photoresponses. However, mapping the ultrafast formation of a long-lived hidden phase remains a longstanding challenge since the initial state is not recovered rapidly. Here, using state-of-the-art single-shot spectroscopy techniques, we present a direct ultrafast visualization of the photoinduced phase transition to both transient and long-lived hidden states in an electronic crystal, 1T-TaS2, and demonstrate a commonality in their microscopic pathways, driven by the collapse of charge order. We present a theory of fluctuation-dominated process that helps explain the nature of the metastable state. Our results shed light on the origin of this elusive state and pave the way for the discovery of other exotic phases of matter.
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Affiliation(s)
- Frank Y. Gao
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Zhuquan Zhang
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Zhiyuan Sun
- Department of Physics, Harvard University, Cambridge, MA 02138, USA
| | - Linda Ye
- Department of Physics, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Yu-Hsiang Cheng
- Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Zi-Jie Liu
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Joseph G. Checkelsky
- Department of Physics, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Edoardo Baldini
- Department of Physics, The University of Texas at Austin, Austin, TX 78712, USA
| | - Keith A. Nelson
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
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10
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Bao C, Li Q, Xu S, Zhou S, Zeng XY, Zhong H, Gao Q, Luo L, Sun D, Xia TL, Zhou S. Population Inversion and Dirac Fermion Cooling in 3D Dirac Semimetal Cd 3As 2. NANO LETTERS 2022; 22:1138-1144. [PMID: 35050626 DOI: 10.1021/acs.nanolett.1c04250] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Revealing the ultrafast dynamics of three-dimensional (3D) Dirac fermions is critical for both fundamental science and device applications. So far, how the cooling of 3D Dirac fermions differs from that of two-dimensional (2D) and whether there is population inversion are fundamental questions to be answered. Here we reveal the ultrafast dynamics of Dirac fermions in a model 3D Dirac semimetal Cd3As2 by time- and angle-resolved photoemission spectroscopy with a tunable probe photon energy. The energy- and momentum-resolved relaxation rate shows a linear dependence on the energy, suggesting Dirac fermion cooling through intraband relaxation. Moreover, a population inversion is reported based on the observation of accumulated photoexcited carriers in the conduction band with a lifetime of 3.0 ps. Our work provides direct experimental evidence for a long-lived population inversion in a 3D Dirac semimetal, which is in contrast to 2D graphene with a much shorter lifetime.
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Affiliation(s)
- Changhua Bao
- State Key Laboratory of Low-Dimensional Quantum Physics and Department of Physics, Tsinghua University, Beijing 100084, P. R. China
| | - Qian Li
- State Key Laboratory of Low-Dimensional Quantum Physics and Department of Physics, Tsinghua University, Beijing 100084, P. R. China
| | - Sheng Xu
- Department of Physics and Beijing Key Laboratory of Opto-electronic Functional Materials and Micro-nano Devices, Renmin University of China, Beijing 100872, P. R. China
| | - Shaohua Zhou
- State Key Laboratory of Low-Dimensional Quantum Physics and Department of Physics, Tsinghua University, Beijing 100084, P. R. China
| | - Xiang-Yu Zeng
- Department of Physics and Beijing Key Laboratory of Opto-electronic Functional Materials and Micro-nano Devices, Renmin University of China, Beijing 100872, P. R. China
| | - Haoyuan Zhong
- State Key Laboratory of Low-Dimensional Quantum Physics and Department of Physics, Tsinghua University, Beijing 100084, P. R. China
| | - Qixuan Gao
- State Key Laboratory of Low-Dimensional Quantum Physics and Department of Physics, Tsinghua University, Beijing 100084, P. R. China
| | - Laipeng Luo
- State Key Laboratory of Low-Dimensional Quantum Physics and Department of Physics, Tsinghua University, Beijing 100084, P. R. China
| | - Dong Sun
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, P. R. China
| | - Tian-Long Xia
- Department of Physics and Beijing Key Laboratory of Opto-electronic Functional Materials and Micro-nano Devices, Renmin University of China, Beijing 100872, P. R. China
| | - Shuyun Zhou
- State Key Laboratory of Low-Dimensional Quantum Physics and Department of Physics, Tsinghua University, Beijing 100084, P. R. China
- Frontier Science Center for Quantum Information, Beijing 100084, P. R. China
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11
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Zhang Y, Shi X, Guan M, You W, Zhong Y, Kafle TR, Huang Y, Ding H, Bauer M, Rossnagel K, Meng S, Kapteyn HC, Murnane MM. Creation of a novel inverted charge density wave state. STRUCTURAL DYNAMICS (MELVILLE, N.Y.) 2022; 9:014501. [PMID: 35071692 PMCID: PMC8759797 DOI: 10.1063/4.0000132] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/12/2021] [Accepted: 12/21/2021] [Indexed: 06/14/2023]
Abstract
Charge density wave (CDW) order is an emergent quantum phase that is characterized by periodic lattice distortion and charge density modulation, often present near superconducting transitions. Here, we uncover a novel inverted CDW state by using a femtosecond laser to coherently reverse the star-of-David lattice distortion in 1T-TaSe2. We track the signature of this novel CDW state using time- and angle-resolved photoemission spectroscopy and the time-dependent density functional theory to validate that it is associated with a unique lattice and charge arrangement never before realized. The dynamic electronic structure further reveals its novel properties that are characterized by an increased density of states near the Fermi level, high metallicity, and altered electron-phonon couplings. Our results demonstrate how ultrafast lasers can be used to create unique states in materials by manipulating charge-lattice orders and couplings.
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Affiliation(s)
- Yingchao Zhang
- Department of Physics and JILA, University of Colorado and NIST, Boulder, Colorado 80309, USA
| | - Xun Shi
- Department of Physics and JILA, University of Colorado and NIST, Boulder, Colorado 80309, USA
| | - Mengxue Guan
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Wenjing You
- Department of Physics and JILA, University of Colorado and NIST, Boulder, Colorado 80309, USA
| | | | - Tika R. Kafle
- Department of Physics and JILA, University of Colorado and NIST, Boulder, Colorado 80309, USA
| | - Yaobo Huang
- Shanghai Synchrotron Radiation Facility, Shanghai Advanced Research Institute, Chinese Academy of Sciences, Shanghai 201204, China
| | - Hong Ding
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Michael Bauer
- Institute of Experimental and Applied Physics, Kiel University, D-24098 Kiel, Germany
| | | | - Sheng Meng
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Henry C. Kapteyn
- Department of Physics and JILA, University of Colorado and NIST, Boulder, Colorado 80309, USA
| | - Margaret M. Murnane
- Department of Physics and JILA, University of Colorado and NIST, Boulder, Colorado 80309, USA
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12
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Dorney KM, Fan T, Nguyen QLD, Ellis JL, Hickstein DD, Brooks N, Zusin D, Gentry C, Hernández-García C, Kapteyn HC, Murnane MM. Bright, single helicity, high harmonics driven by mid-infrared bicircular laser fields. OPTICS EXPRESS 2021; 29:38119-38128. [PMID: 34808871 DOI: 10.1364/oe.440813] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/17/2021] [Accepted: 10/20/2021] [Indexed: 06/13/2023]
Abstract
High-harmonic generation (HHG) is a unique tabletop light source with femtosecond-to-attosecond pulse duration and tailorable polarization and beam shape. Here, we use counter-rotating femtosecond laser pulses of 0.8 µm and 2.0 μm to extend the photon energy range of circularly polarized high-harmonics and also generate single-helicity HHG spectra. By driving HHG in helium, we produce circularly polarized soft x-ray harmonics beyond 170 eV-the highest photon energy of circularly polarized HHG achieved to date. In an Ar medium, dense spectra at photon energies well beyond the Cooper minimum are generated, with regions composed of a single helicity-consistent with the generation of a train of circularly polarized attosecond pulses. Finally, we show theoretically that circularly polarized HHG photon energies can extend beyond the carbon K edge, extending the range of molecular and materials systems that can be accessed using dynamic HHG chiral spectro-microscopies.
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13
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Nakata Y, Sugawara K, Chainani A, Oka H, Bao C, Zhou S, Chuang PY, Cheng CM, Kawakami T, Saruta Y, Fukumura T, Zhou S, Takahashi T, Sato T. Robust charge-density wave strengthened by electron correlations in monolayer 1T-TaSe 2 and 1T-NbSe 2. Nat Commun 2021; 12:5873. [PMID: 34620875 PMCID: PMC8497551 DOI: 10.1038/s41467-021-26105-1] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2021] [Accepted: 09/17/2021] [Indexed: 11/09/2022] Open
Abstract
Combination of low-dimensionality and electron correlation is vital for exotic quantum phenomena such as the Mott-insulating phase and high-temperature superconductivity. Transition-metal dichalcogenide (TMD) 1T-TaS2 has evoked great interest owing to its unique nonmagnetic Mott-insulator nature coupled with a charge-density-wave (CDW). To functionalize such a complex phase, it is essential to enhance the CDW-Mott transition temperature TCDW-Mott, whereas this was difficult for bulk TMDs with TCDW-Mott < 200 K. Here we report a strong-coupling 2D CDW-Mott phase with a transition temperature onset of ~530 K in monolayer 1T-TaSe2. Furthermore, the electron correlation derived lower Hubbard band survives under external perturbations such as carrier doping and photoexcitation, in contrast to the bulk counterpart. The enhanced Mott-Hubbard and CDW gaps for monolayer TaSe2 compared to NbSe2, originating in the lattice distortion assisted by strengthened correlations and disappearance of interlayer hopping, suggest stabilization of a likely nonmagnetic CDW-Mott insulator phase well above the room temperature. The present result lays the foundation for realizing monolayer CDW-Mott insulator based devices operating at room temperature.
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Affiliation(s)
- Yuki Nakata
- Department of Physics, Graduate School of Science, Tohoku University, Sendai, 980-8578, Japan
| | - Katsuaki Sugawara
- Department of Physics, Graduate School of Science, Tohoku University, Sendai, 980-8578, Japan
- Center for Spintronics Research Network, Tohoku University, Sendai, 980-8577, Japan
- Advanced Institute for Materials Research (WPI-AIMR), Tohoku University, Sendai, 980-8577, Japan
| | - Ashish Chainani
- National Synchrotron Radiation Research Center, Hshinchu, 30077, Taiwan ROC
| | - Hirofumi Oka
- Advanced Institute for Materials Research (WPI-AIMR), Tohoku University, Sendai, 980-8577, Japan
| | - Changhua Bao
- State Key Laboratory of Low Dimensional Quantum Physics and Department of Physics, Tsinghua University, Beijing, 100084, China
| | - Shaohua Zhou
- State Key Laboratory of Low Dimensional Quantum Physics and Department of Physics, Tsinghua University, Beijing, 100084, China
| | - Pei-Yu Chuang
- National Synchrotron Radiation Research Center, Hshinchu, 30077, Taiwan ROC
| | - Cheng-Maw Cheng
- National Synchrotron Radiation Research Center, Hshinchu, 30077, Taiwan ROC
| | - Tappei Kawakami
- Department of Physics, Graduate School of Science, Tohoku University, Sendai, 980-8578, Japan
| | - Yasuaki Saruta
- Department of Physics, Graduate School of Science, Tohoku University, Sendai, 980-8578, Japan
| | - Tomoteru Fukumura
- Department of Chemistry, Graduate School of Science, Tohoku University, Sendai, 980-8578, Japan
| | - Shuyun Zhou
- State Key Laboratory of Low Dimensional Quantum Physics and Department of Physics, Tsinghua University, Beijing, 100084, China
- Frontier Science Center for Quantum Information, Beijing, 100084, China
| | - Takashi Takahashi
- Department of Physics, Graduate School of Science, Tohoku University, Sendai, 980-8578, Japan
- Center for Spintronics Research Network, Tohoku University, Sendai, 980-8577, Japan
- Advanced Institute for Materials Research (WPI-AIMR), Tohoku University, Sendai, 980-8577, Japan
| | - Takafumi Sato
- Department of Physics, Graduate School of Science, Tohoku University, Sendai, 980-8578, Japan.
- Center for Spintronics Research Network, Tohoku University, Sendai, 980-8577, Japan.
- Advanced Institute for Materials Research (WPI-AIMR), Tohoku University, Sendai, 980-8577, Japan.
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14
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Lloyd-Hughes J, Oppeneer PM, Pereira Dos Santos T, Schleife A, Meng S, Sentef MA, Ruggenthaler M, Rubio A, Radu I, Murnane M, Shi X, Kapteyn H, Stadtmüller B, Dani KM, da Jornada FH, Prinz E, Aeschlimann M, Milot RL, Burdanova M, Boland J, Cocker T, Hegmann F. The 2021 ultrafast spectroscopic probes of condensed matter roadmap. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2021; 33:353001. [PMID: 33951618 DOI: 10.1088/1361-648x/abfe21] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/25/2020] [Accepted: 05/05/2021] [Indexed: 06/12/2023]
Abstract
In the 60 years since the invention of the laser, the scientific community has developed numerous fields of research based on these bright, coherent light sources, including the areas of imaging, spectroscopy, materials processing and communications. Ultrafast spectroscopy and imaging techniques are at the forefront of research into the light-matter interaction at the shortest times accessible to experiments, ranging from a few attoseconds to nanoseconds. Light pulses provide a crucial probe of the dynamical motion of charges, spins, and atoms on picosecond, femtosecond, and down to attosecond timescales, none of which are accessible even with the fastest electronic devices. Furthermore, strong light pulses can drive materials into unusual phases, with exotic properties. In this roadmap we describe the current state-of-the-art in experimental and theoretical studies of condensed matter using ultrafast probes. In each contribution, the authors also use their extensive knowledge to highlight challenges and predict future trends.
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Affiliation(s)
- J Lloyd-Hughes
- Department of Physics, University of Warwick, Gibbet Hill Road, Coventry, CV4 7AL, United Kingdom
| | - P M Oppeneer
- Department of Physics and Astronomy, Uppsala University, PO Box 516, S-75120 Uppsala, Sweden
| | - T Pereira Dos Santos
- Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801, United States of America
| | - A Schleife
- Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801, United States of America
- Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, IL 61801, United States of America
- National Center for Supercomputing Applications, University of Illinois at Urbana-Champaign, Urbana, IL 61801, United States of America
| | - S Meng
- Institute of Physics, Chinese Academy of Sciences, Beijing, People's Republic of China
| | - M A Sentef
- Max Planck Institute for the Structure and Dynamics of Matter, Center for Free Electron Laser Science (CFEL), 22761 Hamburg, Germany
| | - M Ruggenthaler
- Max Planck Institute for the Structure and Dynamics of Matter, Center for Free Electron Laser Science (CFEL), 22761 Hamburg, Germany
| | - A Rubio
- Max Planck Institute for the Structure and Dynamics of Matter, Center for Free Electron Laser Science (CFEL), 22761 Hamburg, Germany
- Nano-Bio Spectroscopy Group and ETSF, Universidad del País Vasco UPV/EHU 20018 San Sebastián, Spain
- Center for Computational Quantum Physics (CCQ), The Flatiron Institute, 162 Fifth Avenue, New York, NY, 10010, United States of America
| | - I Radu
- Department of Physics, Freie Universität Berlin, Germany
- Max Born Institute, Berlin, Germany
| | - M Murnane
- JILA, University of Colorado and NIST, Boulder, CO, United States of America
| | - X Shi
- JILA, University of Colorado and NIST, Boulder, CO, United States of America
| | - H Kapteyn
- JILA, University of Colorado and NIST, Boulder, CO, United States of America
| | - B Stadtmüller
- Department of Physics and Research Center OPTIMAS, University of Kaiserslautern, 67663 Kaiserslautern, Germany
| | - K M Dani
- Femtosecond Spectroscopy Unit, Okinawa Institute of Science and Technology Graduate University, Onna-son, Japan
| | - F H da Jornada
- Department of Materials Science and Engineering, Stanford University, Stanford, 94305, CA, United States of America
| | - E Prinz
- Department of Physics and Research Center OPTIMAS, University of Kaiserslautern, 67663 Kaiserslautern, Germany
| | - M Aeschlimann
- Department of Physics and Research Center OPTIMAS, University of Kaiserslautern, 67663 Kaiserslautern, Germany
| | - R L Milot
- Department of Physics, University of Warwick, Gibbet Hill Road, Coventry, CV4 7AL, United Kingdom
| | - M Burdanova
- Department of Physics, University of Warwick, Gibbet Hill Road, Coventry, CV4 7AL, United Kingdom
| | - J Boland
- Photon Science Institute, Department of Electrical and Electronic Engineering, University of Manchester, United Kingdom
| | - T Cocker
- Michigan State University, United States of America
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15
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Yang LX, Rohde G, Hanff K, Stange A, Xiong R, Shi J, Bauer M, Rossnagel K. Bypassing the Structural Bottleneck in the Ultrafast Melting of Electronic Order. PHYSICAL REVIEW LETTERS 2020; 125:266402. [PMID: 33449703 DOI: 10.1103/physrevlett.125.266402] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/29/2020] [Accepted: 11/23/2020] [Indexed: 06/12/2023]
Abstract
Impulsive optical excitation generally results in a complex nonequilibrium electron and lattice dynamics that involves multiple processes on distinct timescales, and a common conception is that for times shorter than about 100 fs the gap in the electronic spectrum is not seriously affected by lattice vibrations. Here, however, by directly monitoring the photoinduced collapse of the spectral gap in a canonical charge-density-wave material, the blue bronze Rb_{0.3}MoO_{3}, we find that ultrafast (∼60 fs) vibrational disordering due to efficient hot-electron energy dissipation quenches the gap significantly faster than the typical structural bottleneck time corresponding to one half-cycle oscillation (∼315 fs) of the coherent charge-density-wave amplitude mode. This result not only demonstrates the importance of incoherent lattice motion in the photoinduced quenching of electronic order, but also resolves the perennial debate about the nature of the spectral gap in a coupled electron-lattice system.
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Affiliation(s)
- L X Yang
- State Key Laboratory of Low Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, People's Republic of China
- Institut für Experimentelle und Angewandte Physik, Christian-Albrechts-Universität zu Kiel, 24098 Kiel, Germany
- Frontier Science Center for Quantum Information, Beijing 100084, People's Republic of China
| | - G Rohde
- Institut für Experimentelle und Angewandte Physik, Christian-Albrechts-Universität zu Kiel, 24098 Kiel, Germany
| | - K Hanff
- Institut für Experimentelle und Angewandte Physik, Christian-Albrechts-Universität zu Kiel, 24098 Kiel, Germany
| | - A Stange
- Institut für Experimentelle und Angewandte Physik, Christian-Albrechts-Universität zu Kiel, 24098 Kiel, Germany
| | - R Xiong
- Department of Physics, Wuhan University, Wuhan 430072, People's Republic of China
| | - J Shi
- Department of Physics, Wuhan University, Wuhan 430072, People's Republic of China
| | - M Bauer
- Institut für Experimentelle und Angewandte Physik, Christian-Albrechts-Universität zu Kiel, 24098 Kiel, Germany
| | - K Rossnagel
- Institut für Experimentelle und Angewandte Physik, Christian-Albrechts-Universität zu Kiel, 24098 Kiel, Germany
- Ruprecht-Haensel-Labor, Deutsches Elektronen-Synchrotron DESY, 22607 Hamburg, Germany
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16
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Maklar J, Dong S, Beaulieu S, Pincelli T, Dendzik M, Windsor YW, Xian RP, Wolf M, Ernstorfer R, Rettig L. A quantitative comparison of time-of-flight momentum microscopes and hemispherical analyzers for time- and angle-resolved photoemission spectroscopy experiments. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2020; 91:123112. [PMID: 33379994 DOI: 10.1063/5.0024493] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/07/2020] [Accepted: 11/26/2020] [Indexed: 06/12/2023]
Abstract
Time-of-flight-based momentum microscopy has a growing presence in photoemission studies, as it enables parallel energy- and momentum-resolved acquisition of the full photoelectron distribution. Here, we report table-top extreme ultraviolet time- and angle-resolved photoemission spectroscopy (trARPES) featuring both a hemispherical analyzer and a momentum microscope within the same setup. We present a systematic comparison of the two detection schemes and quantify experimentally relevant parameters, including pump- and probe-induced space-charge effects, detection efficiency, photoelectron count rates, and depth of focus. We highlight the advantages and limitations of both instruments based on exemplary trARPES measurements of bulk WSe2. Our analysis demonstrates the complementary nature of the two spectrometers for time-resolved ARPES experiments. Their combination in a single experimental apparatus allows us to address a broad range of scientific questions with trARPES.
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Affiliation(s)
- J Maklar
- Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, D-14195 Berlin, Germany
| | - S Dong
- Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, D-14195 Berlin, Germany
| | - S Beaulieu
- Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, D-14195 Berlin, Germany
| | - T Pincelli
- Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, D-14195 Berlin, Germany
| | - M Dendzik
- Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, D-14195 Berlin, Germany
| | - Y W Windsor
- Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, D-14195 Berlin, Germany
| | - R P Xian
- Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, D-14195 Berlin, Germany
| | - M Wolf
- Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, D-14195 Berlin, Germany
| | - R Ernstorfer
- Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, D-14195 Berlin, Germany
| | - L Rettig
- Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, D-14195 Berlin, Germany
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17
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Storeck G, Horstmann JG, Diekmann T, Vogelgesang S, von Witte G, Yalunin SV, Rossnagel K, Ropers C. Structural dynamics of incommensurate charge-density waves tracked by ultrafast low-energy electron diffraction. STRUCTURAL DYNAMICS (MELVILLE, N.Y.) 2020; 7:034304. [PMID: 32596414 PMCID: PMC7311179 DOI: 10.1063/4.0000018] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/07/2020] [Accepted: 04/13/2020] [Indexed: 06/11/2023]
Abstract
We study the non-equilibrium structural dynamics of the incommensurate and nearly commensurate charge-density wave (CDW) phases in 1T-TaS 2 . Employing ultrafast low-energy electron diffraction with 1 ps temporal resolution, we investigate the ultrafast quench and recovery of the CDW-coupled periodic lattice distortion (PLD). Sequential structural relaxation processes are observed by tracking the intensities of main lattice as well as satellite diffraction peaks and the diffuse scattering background. Comparing distinct groups of diffraction peaks, we disentangle the ultrafast quench of the PLD amplitude from phonon-related reductions of the diffraction intensity. Fluence-dependent relaxation cycles reveal a long-lived partial suppression of the order parameter for up to 60 ps, far outlasting the initial amplitude recovery and electron-phonon scattering times. This delayed return to a quasi-thermal level is controlled by lattice thermalization and coincides with the population of zone-center acoustic modes, as evidenced by a structured diffuse background. The long-lived non-equilibrium order parameter suppression suggests hot populations of CDW-coupled lattice modes. Finally, a broadening of the superlattice peaks is observed at high fluences, pointing to a non-linear generation of phase fluctuations.
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Affiliation(s)
- G. Storeck
- 4th Physical Institute, Solids and Nanostructures, University of Göttingen, 37077 Göttingen, Germany
| | - J. G. Horstmann
- 4th Physical Institute, Solids and Nanostructures, University of Göttingen, 37077 Göttingen, Germany
| | - T. Diekmann
- 4th Physical Institute, Solids and Nanostructures, University of Göttingen, 37077 Göttingen, Germany
| | - S. Vogelgesang
- 4th Physical Institute, Solids and Nanostructures, University of Göttingen, 37077 Göttingen, Germany
| | - G. von Witte
- 4th Physical Institute, Solids and Nanostructures, University of Göttingen, 37077 Göttingen, Germany
| | - S. V. Yalunin
- 4th Physical Institute, Solids and Nanostructures, University of Göttingen, 37077 Göttingen, Germany
| | | | - C. Ropers
- Author to whom correspondence should be addressed:
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18
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Coherent modulation of the electron temperature and electron-phonon couplings in a 2D material. Proc Natl Acad Sci U S A 2020; 117:8788-8793. [PMID: 32241890 DOI: 10.1073/pnas.1917341117] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Ultrashort light pulses can selectively excite charges, spins, and phonons in materials, providing a powerful approach for manipulating their properties. Here we use femtosecond laser pulses to coherently manipulate the electron and phonon distributions, and their couplings, in the charge-density wave (CDW) material 1T-TaSe2 After exciting the material with a femtosecond pulse, fast spatial smearing of the laser-excited electrons launches a coherent lattice breathing mode, which in turn modulates the electron temperature. This finding is in contrast to all previous observations in multiple materials to date, where the electron temperature decreases monotonically via electron-phonon scattering. By tuning the laser fluence, the magnitude of the electron temperature modulation changes from ∼200 K in the case of weak excitation, to ∼1,000 K for strong laser excitation. We also observe a phase change of π in the electron temperature modulation at a critical fluence of 0.7 mJ/cm2, which suggests a switching of the dominant coupling mechanism between the coherent phonon and electrons. Our approach opens up routes for coherently manipulating the interactions and properties of two-dimensional and other quantum materials using light.
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19
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Liu Y, Beetar JE, Hosen MM, Dhakal G, Sims C, Kabir F, Etienne MB, Dimitri K, Regmi S, Liu Y, Pathak AK, Kaczorowski D, Neupane M, Chini M. Extreme ultraviolet time- and angle-resolved photoemission setup with 21.5 meV resolution using high-order harmonic generation from a turn-key Yb:KGW amplifier. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2020; 91:013102. [PMID: 32012559 DOI: 10.1063/1.5121425] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/24/2019] [Accepted: 12/15/2019] [Indexed: 06/10/2023]
Abstract
Characterizing and controlling electronic properties of quantum materials require direct measurements of nonequilibrium electronic band structures over large regions of momentum space. Here, we demonstrate an experimental apparatus for time- and angle-resolved photoemission spectroscopy using high-order harmonic probe pulses generated by a robust, moderately high power (20 W) Yb:KGW amplifier with a tunable repetition rate between 50 and 150 kHz. By driving high-order harmonic generation (HHG) with the second harmonic of the fundamental 1025 nm laser pulses, we show that single-harmonic probe pulses at 21.8 eV photon energy can be effectively isolated without the use of a monochromator. The on-target photon flux can reach 5 × 1010 photons/s at 50 kHz, and the time resolution is measured to be 320 fs. The relatively long pulse duration of the Yb-driven HHG source allows us to reach an excellent energy resolution of 21.5 meV, which is achieved by suppressing the space-charge broadening using a low photon flux of 1.5 × 108 photons/s at a higher repetition rate of 150 kHz. The capabilities of the setup are demonstrated through measurements in the topological semimetal ZrSiS and the topological insulator Sb2-xGdxTe3.
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Affiliation(s)
- Yangyang Liu
- Department of Physics, University of Central Florida, Orlando, Florida 32816, USA
| | - John E Beetar
- Department of Physics, University of Central Florida, Orlando, Florida 32816, USA
| | - Md Mofazzel Hosen
- Department of Physics, University of Central Florida, Orlando, Florida 32816, USA
| | - Gyanendra Dhakal
- Department of Physics, University of Central Florida, Orlando, Florida 32816, USA
| | - Christopher Sims
- Department of Physics, University of Central Florida, Orlando, Florida 32816, USA
| | - Firoza Kabir
- Department of Physics, University of Central Florida, Orlando, Florida 32816, USA
| | - Marc B Etienne
- Department of Physics, University of Central Florida, Orlando, Florida 32816, USA
| | - Klauss Dimitri
- Department of Physics, University of Central Florida, Orlando, Florida 32816, USA
| | - Sabin Regmi
- Department of Physics, University of Central Florida, Orlando, Florida 32816, USA
| | - Yong Liu
- Ames Laboratory, U.S. Department of Energy, Ames, Iowa 50011-3020, USA
| | - Arjun K Pathak
- Ames Laboratory, U.S. Department of Energy, Ames, Iowa 50011-3020, USA
| | - Dariusz Kaczorowski
- Institute of Low Temperature and Structure Research, Polish Academy of Sciences, PL-50-950 Wroclaw, Poland
| | - Madhab Neupane
- Department of Physics, University of Central Florida, Orlando, Florida 32816, USA
| | - Michael Chini
- Department of Physics, University of Central Florida, Orlando, Florida 32816, USA
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