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Yang S, Liu X, Zhang H, Song X, Zuo R, Meier T, Yang W. Sub-cycle strong-field tunneling dynamics in solids. OPTICS EXPRESS 2024; 32:15862-15869. [PMID: 38859226 DOI: 10.1364/oe.521207] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/07/2024] [Accepted: 03/27/2024] [Indexed: 06/12/2024]
Abstract
Tunneling ionization is a crucial process in the interaction between strong laser fields and matter which initiates numerous nonlinear phenomena including high-order harmonic generation, photoelectron holography, etc. Both adiabatic and nonadiabatic tunneling ionization are well understood in atomic systems. However, the tunneling dynamics in solids, especially nonadiabatic tunneling, has not yet been fully understood. Here, we study the sub-cycle resolved strong-field tunneling dynamics in solids via a complex saddle-point method. We compare the instantaneous momentum at the moment of tunneling and the tunneling distances over a range of Keldysh parameters. Our results demonstrate that for nonadiabatic tunneling, tunneling ionization away from Γ point is possible. When this happens the electron has a nonzero initial velocity when it emerges in the conduction band. Moreover, consistent with atomic tunneling, a reduced tunneling distance as compared to the quasi-static case is found. Our results provide remarkable insight into the basic physics governing the sub-cycle electron tunneling dynamics with significant implications for understanding subsequent strong-field nonlinear phenomena in solids.
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Ortmann L, AlShafey A, Staudte A, Landsman AS. Tracking the Ionization Site in Neutral Molecules. PHYSICAL REVIEW LETTERS 2021; 127:213201. [PMID: 34860111 DOI: 10.1103/physrevlett.127.213201] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/16/2020] [Revised: 09/19/2021] [Accepted: 10/15/2021] [Indexed: 06/13/2023]
Abstract
When a diatomic molecule is exposed to intense light, the valence electron may tunnel from a higher potential (corresponding to an upfield atom) due to the suppressed internuclear barrier. This process is known as ionization enhancement and is a key mechanism in strong field ionization of molecules. Alternatively, the bound electron wave function can evolve adiabatically in the laser field, resulting in ionization from the downfield atom. Here, we introduce a method to quantify the relative contribution of these two processes. Applying this method to experimentally measured electron momenta distributions following strong field ionization of N_{2} with infrared laser light, we find approximately a 2∶1 ratio of electrons ionized from a downfield atom, relative to upfield. This suggests that the bound state wave function largely adapts adiabatically to the changing laser field, although the nonadiabatic process of ionization enhancement still contributes even in neutral molecules. Our method can be applied to any diatomic neutral molecule to better understand the evolution of the initially bound electron wave packet and hence the nature of the molecular ionization process.
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Affiliation(s)
- L Ortmann
- Max Planck Institute for the Physics of Complex Systems, Nöthnitzer Straße 38, D-01187 Dresden, Germany
- Department of Physics, The Ohio State University, Columbus, Ohio 43210, USA
| | - A AlShafey
- Department of Physics, The Ohio State University, Columbus, Ohio 43210, USA
| | - A Staudte
- Joint Attosecond Science Lab of the National Research Council and the University of Ottawa, Ottawa, Ontario K1A 0R6, Canada
| | - A S Landsman
- Department of Physics, The Ohio State University, Columbus, Ohio 43210, USA
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Ben S, Chen S, Bi CR, Chen J, Liu XS. Investigation of electron vortices in time-delayed circularly polarized laser pulses with a semiclassical perspective. OPTICS EXPRESS 2020; 28:29442-29454. [PMID: 33114844 DOI: 10.1364/oe.400846] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/22/2020] [Accepted: 09/06/2020] [Indexed: 06/11/2023]
Abstract
We theoretically investigate strong-filed electron vortices in time-delayed circularly polarized laser pulses by a generalized quantum-trajectory Monte Carlo (GQTMC) model. Vortex interference patterns in photoelectron momentum distributions (PMDs) with various laser parameters can be well reproduced by the semiclassical simulation. The phase difference responsible for the interference structures is analytically identified through trajectory-based analysis and simple-man theory, which reveal the underlying mechanism of electron vortex phenomena for both co-rotating and counter-rotating component. This semiclassical analysis can also demonstrate the influences of laser intensity and wavelength on the number of arms of vortices. Furthermore, we show the influence of the Coulomb effect on the PMDs. Finally, the controlling of the ionization time intervals in the tens to hundreds of attosecond magnitude is qualitatively discussed.
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Liu X, Zhang G, Li J, Shi G, Zhou M, Huang B, Tang Y, Song X, Yang W. Deep Learning for Feynman's Path Integral in Strong-Field Time-Dependent Dynamics. PHYSICAL REVIEW LETTERS 2020; 124:113202. [PMID: 32242706 DOI: 10.1103/physrevlett.124.113202] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/18/2019] [Revised: 02/23/2020] [Accepted: 02/28/2020] [Indexed: 06/11/2023]
Abstract
Feynman's path integral approach is to sum over all possible spatiotemporal paths to reproduce the quantum wave function and the corresponding time evolution, which has enormous potential to reveal quantum processes in the classical view. However, the complete characterization of the quantum wave function with infinite paths is a formidable challenge, which greatly limits the application potential, especially in the strong-field physics and attosecond science. Instead of brute-force tracking every path one by one, here we propose a deep-learning-performed strong-field Feynman's formulation with a preclassification scheme that can predict directly the final results only with data of initial conditions, so as to attack unsurmountable tasks by existing strong-field methods and explore new physics. Our results build a bridge between deep learning and strong-field physics through Feynman's path integral, which would boost applications of deep learning to study the ultrafast time-dependent dynamics in strong-field physics and attosecond science and shed new light on the quantum-classical correspondence.
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Affiliation(s)
- Xiwang Liu
- Research Center for Advanced Optics and Photoelectronics, Department of Physics, College of Science, Shantou University, Shantou, Guangdong 515063, China
- Department of Mathematics, College of Science, Shantou University, Shantou, Guangdong 515063, China
| | - Guojun Zhang
- Research Center for Advanced Optics and Photoelectronics, Department of Physics, College of Science, Shantou University, Shantou, Guangdong 515063, China
| | - Jie Li
- Research Center for Advanced Optics and Photoelectronics, Department of Physics, College of Science, Shantou University, Shantou, Guangdong 515063, China
| | - Guangluo Shi
- Research Center for Advanced Optics and Photoelectronics, Department of Physics, College of Science, Shantou University, Shantou, Guangdong 515063, China
| | - Mingyang Zhou
- Research Center for Advanced Optics and Photoelectronics, Department of Physics, College of Science, Shantou University, Shantou, Guangdong 515063, China
| | - Boqiang Huang
- Mathematisches Institut, Universität zu Köln, 50931 Köln, Germany
| | - Yajuan Tang
- Department of Electronic and Information Engineering, College of Engineering, Shantou University, Shantou, Guangdong 515063, China
| | - Xiaohong Song
- Research Center for Advanced Optics and Photoelectronics, Department of Physics, College of Science, Shantou University, Shantou, Guangdong 515063, China
- Department of Mathematics, College of Science, Shantou University, Shantou, Guangdong 515063, China
- Key Laboratory of Intelligent Manufacturing Technology of MOE, Shantou University, Shantou, Guangdong 515063, China
| | - Weifeng Yang
- Research Center for Advanced Optics and Photoelectronics, Department of Physics, College of Science, Shantou University, Shantou, Guangdong 515063, China
- Department of Mathematics, College of Science, Shantou University, Shantou, Guangdong 515063, China
- Key Laboratory of Intelligent Manufacturing Technology of MOE, Shantou University, Shantou, Guangdong 515063, China
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Song X, Shi G, Zhang G, Xu J, Lin C, Chen J, Yang W. Attosecond Time Delay of Retrapped Resonant Ionization. PHYSICAL REVIEW LETTERS 2018; 121:103201. [PMID: 30240251 DOI: 10.1103/physrevlett.121.103201] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/10/2018] [Revised: 07/10/2018] [Indexed: 06/08/2023]
Abstract
A recent ultrafast pump-probe technique has allowed measurement of time delays during photoemission in a variety of systems ranging from atoms and molecules to solids with unprecedented temporal resolution. However, identifying the underlying physics is still a challenge especially in complicated multichannel above-threshold ionization (ATI) experiments. Here we demonstrate that the time delays of different ionization pathways in ATI can be clearly resolved and extracted with a semiclassical statistical method. The remarkable phase shift of near threshold photoelectrons can be attributed to a temporary retrapping of a photoelectron by the atomic potential in a quasibound state after emerging in the continuum state. This continuum-bound-continuum scattering manifests as a new resonant effect in strong-field photoemission. Our results unify the seemingly opposing quantum Eisenbud-Wigner-Smith time delay and classical Coulomb-induced time delay by highlighting the same physical picture, which holds promise for an intuitive interpretation of time-resolved fundamental electronic processes in strong-field experiments and epistemological reexamination of the quantum-classical correspondence.
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Affiliation(s)
- Xiaohong Song
- Department of Physics, College of Science, Shantou University, Shantou, Guangdong 515063, China
| | - Guangluo Shi
- Department of Physics, College of Science, Shantou University, Shantou, Guangdong 515063, China
| | - Guojun Zhang
- Department of Physics, College of Science, Shantou University, Shantou, Guangdong 515063, China
| | - Jingwen Xu
- Department of Physics, College of Science, Shantou University, Shantou, Guangdong 515063, China
| | - Cheng Lin
- Department of Physics, College of Science, Shantou University, Shantou, Guangdong 515063, China
| | - Jing Chen
- Key Laboratory of High Energy Density Physics Simulation, Center for Applied Physics and Technology, Peking University, Beijing 100084, China
- Institute of Applied Physics and Computational Mathematics, P.O. Box 8009, Beijing 100088, China
- Collaborative Innovation Center of Inertial Fusion Sciences and Applications, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Weifeng Yang
- Department of Physics, College of Science, Shantou University, Shantou, Guangdong 515063, China
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Liu K, Barth I. Identifying the Tunneling Site in Strong-Field Ionization of H_{2}^{+}. PHYSICAL REVIEW LETTERS 2017; 119:243204. [PMID: 29286733 DOI: 10.1103/physrevlett.119.243204] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/30/2017] [Indexed: 06/07/2023]
Abstract
The tunneling site of the electron in a molecule exposed to a strong laser field determines the initial position of the ionizing electron and, as a result, has a large impact on the subsequent ultrafast electron dynamics on the polyatomic Coulomb potential. Here, the tunneling site of the electron of H_{2}^{+} ionized by a strong circularly polarized (CP) laser pulse is studied by numerically solving the time-dependent Schrödinger equation. We show that the electron removed from the down-field site is directly driven away by the CP field and the lateral photoelectron momentum distribution (LPMD) exhibits a Gaussian-like distribution, whereas the corresponding LPMD of the electron removed from the up-field site differs from the Gaussian shape due to the Coulomb focusing and scattering by the down-field core. Our current study presents the direct evidence clarifying a long-standing controversy over the tunneling site in H_{2}^{+} and raises the important role of the tunneling site in strong-field molecular ionization.
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Affiliation(s)
- Kunlong Liu
- Max-Planck-Institut für Mikrostrukturphysik, Weinberg 2, D-06120 Halle (Saale), Germany
| | - Ingo Barth
- Max-Planck-Institut für Mikrostrukturphysik, Weinberg 2, D-06120 Halle (Saale), Germany
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Gong X, Lin C, He F, Song Q, Lin K, Ji Q, Zhang W, Ma J, Lu P, Liu Y, Zeng H, Yang W, Wu J. Energy-Resolved Ultrashort Delays of Photoelectron Emission Clocked by Orthogonal Two-Color Laser Fields. PHYSICAL REVIEW LETTERS 2017; 118:143203. [PMID: 28430519 DOI: 10.1103/physrevlett.118.143203] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/16/2016] [Indexed: 06/07/2023]
Abstract
A phase-controlled orthogonal two-color (OTC) femtosecond laser pulse is employed to probe the time delay of photoelectron emission in the strong-field ionization of atoms. The OTC field spatiotemporally steers the emission dynamics of the photoelectrons and meanwhile allows us to unambiguously distinguish the main and sideband peaks of the above-threshold ionization spectrum. The relative phase shift between the main and sideband peaks, retrieved from the phase-of-phase of the photoelectron spectrum as a function of the laser phase, gradually decreases with increasing electron energy, and becomes zero for the fast electron which is mainly produced by the rescattering process. Furthermore, a Freeman resonance delay of 140±40 attoseconds between photoelectrons emitted via the 4f and 5p Rydberg states of argon is observed.
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Affiliation(s)
- Xiaochun Gong
- State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200062, China
| | - Cheng Lin
- Department of Physics, College of Science, Shantou University, Shantou, Guangdong 515063, China
| | - Feng He
- Key Laboratory of Laser Plasmas (Ministry of Education) and Department of Physics and Astronomy, Collaborative Innovation Center for IFSA (CICIFSA), Shanghai Jiao Tong University, Shanghai 200240, China
| | - Qiying Song
- State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200062, China
| | - Kang Lin
- State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200062, China
| | - Qinying Ji
- State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200062, China
| | - Wenbin Zhang
- State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200062, China
| | - Junyang Ma
- State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200062, China
| | - Peifen Lu
- State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200062, China
| | - Yunquan Liu
- Department of Physics and State Key Laboratory for Mesoscopic Physics, Peking University, Beijing 100871, China
| | - Heping Zeng
- State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200062, China
| | - Weifeng Yang
- Department of Physics, College of Science, Shantou University, Shantou, Guangdong 515063, China
| | - Jian Wu
- State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200062, China
- Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan, Shanxi 030006, China
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