東北大学研究者紹介

研究者詳細

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顔写真

サトウ　シユンスケ

佐藤　駿丞

Shunsuke Sato

所属

大学院理学研究科　物理学専攻　固体統計物理学講座（物性理論分野）

職名

准教授

学位

博士(理学) （筑波大学）

researchmap

https://researchmap.jp/shunsuke_a_sato

J-GLOBAL ID

201901018823735962

ORCID

https://orcid.org/0000-0001-9543-2620

Researcher ID

I-3294-2015

経歴 9

2025年2月～継続中

東北大学　理学部物理学科　准教授
2019年5月～継続中

マックスプランク物質構造・ダイナミクス研究所　客員研究員
2024年5月～ 2025年1月

筑波大学　計算科学研究センター　准教授
2019年5月～ 2024年4月

筑波大学　計算科学研究センター　助教
2017年6月～ 2019年5月

マックスプランク物質構造・ダイナミクス研究所　Alexander von Humboldt研究員
2017年4月～ 2017年5月

マックスプランク物質構造・ダイナミクス研究所　博士研究員
2016年4月～ 2017年3月

マックスプランク物質構造・ダイナミクス研究所　客員研究員
2016年4月～ 2017年3月

筑波大学　計算科学研究センター　日本学術振興会特別研究員(PD)
2014年4月～ 2016年3月

筑波大学　数理物質科学研究科　日本学術振興会特別研究員(DC1)

︎全件表示 ︎最初の5件までを表示

学歴 3

筑波大学　数理物質科学研究科　物理学専攻博士後期課程

2014年4月～ 2016年3月
筑波大学　数理物質科学研究科　物理学専攻博士前期課程

2012年4月～ 2014年3月
筑波大学　理工学群　物理学類

2008年4月～ 2012年3月

研究キーワード 4

超高速現象
時間依存密度汎関数理論
第一原理計算
光物性

研究分野 1

自然科学一般 / 半導体、光物性、原子物理 /

受賞 2

凝縮系科学賞

2024年11月
日本物理学会若手奨励賞

2020年3月　日本物理学会

論文 88

Local fields reveal atomic-scale nonadiabatic carrier-phonon dynamics 査読有り

Sergej Neb, Dong-bin Shin, Florence Burri, Marko Hollm, Erik W. de Vos, Denis A. Kuznetsov, Christoph R. Müller, Alexey Fedorov, Shunsuke A. Sato, Angel Rubio, Lukas Gallmann, Ursula Keller

Science　391　(6780)　75-78　2026年1月
出版者・発行元： American Association for the Advancement of Science (AAAS)
DOI： 10.1126/science.aea1523 　

ISSN：0036-8075

eISSN：1095-9203

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Understanding nonadiabatic carrier-lattice interactions at the atomic scale remains a fundamental challenge, yet these processes govern energy transfer in materials and ultimately set limits in microelectronics. We combined attosecond core-level transient absorption spectroscopy with many-body theory to uncover how nonadiabatic electron-phonon coupling drives ultrafast relaxations in a titanium-carbide MXene. Phonon-driven changes in carrier localization modulated local field effects (LFEs), yielding carrier-, site-, and orbital-specific absorption signatures. LFEs served as sensitive fingerprints of electron-phonon coupling strength across the phonon spectrum and revealed a breakdown of the Born–Oppenheimer approximation: Electrons lagged lattice oscillations by 32 ± 8 femtoseconds, whereas holes responded almost instantaneously (7 ± 7 femtoseconds). Our results establish a framework for probing and controlling nonadiabatic carrier-phonon interactions with orbital and site specificity.
Multistate control of nonlinear photocurrents in ferroelectric IV-monochalcogenide monolayers via phase manipulation of the light field 査読有り

Ali Kazempour, Esmaeil Taghizadeh Sisakht, Mahmut Sait Okyay, Xiao Jiang, Shunsuke Sato, Jinseok Oh, Noejung Park

Communications Physics　8　(1)　2025年11月17日
出版者・発行元： Springer Science and Business Media LLC
DOI： 10.1038/s42005-025-02337-1 　

eISSN：2399-3650
Technical review: Time-dependent density functional theory for attosecond physics ranging from gas-phase to solids 査読有り

Shunsuke A. Sato, Hannes Hübener, Umberto De Giovannini, Angel Rubio

npj Computational Materials　11　(1)　2025年7月15日
出版者・発行元： Springer Science and Business Media LLC
DOI： 10.1038/s41524-025-01715-1 　

eISSN：2057-3960

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Abstract First-principles electron dynamics calculations can be applied in the investigation of a wide range of ultrafast phenomena in attosecond physics. They offer unique microscopic insight into light-induced ultrafast phenomena in both gas and condensed phases of matter, and thus, they are a powerful tool to develop our understanding of the physics of attosecond phenomena. We specifically review techniques employing time-dependent density functional theory (TDDFT) for investigating attosecond and strong-field phenomena. First, we describe this theoretical framework that enables the modeling of perturbative and non-perturbative electron dynamics in materials, including atoms, molecules, and solids. We then discuss its application to attosecond experiments, focusing on the reconstruction of attosecond beating by interference of two-photon transitions (RABBIT) measurements. We also briefly review first-principles calculations of optical properties of solids with TDDFT in the linear response regime and their extension to calculations of transient optical properties of solids in non-equilibrium phases, by simulating experimental pump-probe setups. We further demonstrate the application of TDDFT simulation to high-order harmonic generation in solids. First-principles calculations have predictive power, and hence they can be utilized to design future experiments to explore non-equilibrium and nonlinear ultrafast phenomena in matter and characterize and control metastable light-induced quantum states.
Nonlinear Photocurrent as a Hallmark of Altermagnet 査読有り

Xiao Jiang, Uiseok Jeong, Shunsuke Sato, Dongbin Shin, Kazuhiro Yabana, Binghai Yan, Noejung Park

ACS Nano　19　(26)　23620-23628　2025年6月26日
出版者・発行元： American Chemical Society (ACS)
DOI： 10.1021/acsnano.5c01421 　

ISSN：1936-0851

eISSN：1936-086X
Attosecond virtual charge dynamics in dielectrics 査読有り

Gian Luca Dolso, Shunsuke A. Sato, Giacomo Inzani, Nicola Di Palo, Bruno Moio, Rocío Borrego-Varillas, Mauro Nisoli, Matteo Lucchini

Nature Photonics　19　(9)　999-1005　2025年6月16日
出版者・発行元： Springer Science and Business Media LLC
DOI： 10.1038/s41566-025-01700-6 　

ISSN：1749-4885

eISSN：1749-4893
Initial electron thermalization in metals measured by attosecond transient absorption spectroscopy 査読有り

Bethany R. de Roulet, Lorenz Drescher, Shunsuke A. Sato, Stephen R. Leone

Physical Review B　110　(17)　2024年11月4日
出版者・発行元： American Physical Society (APS)
DOI： 10.1103/physrevb.110.174301 　

ISSN：2469-9950

eISSN：2469-9969
Hot electron effect in high-order harmonic generation from graphene driven by elliptically polarized light 査読有り

Kotaro Nakagawa, Wenwen Mao, Shunsuke A. Sato, Hiroki Ago, Angel Rubio, Yoshihiko Kanemitsu, Hideki Hirori

APL Photonics　9　(7)　2024年7月1日
出版者・発行元： AIP Publishing
DOI： 10.1063/5.0212022 　

eISSN：2378-0967

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We studied high-order harmonic generation (HHG) in graphene driven by either linearly or elliptically polarized mid-infrared (MIR) light, and we additionally applied terahertz (THz) pulses to modulate the electron distribution in graphene. The high-harmonic spectrum obtained using linearly polarized MIR light contains only odd-order harmonics. We found that the intensities of the fifth- and seventh-order harmonics are reduced by the modulation with the THz pulses. In addition, we found that the THz-induced reduction of the seventh-order harmonic driven by elliptically polarized MIR light (at ellipticity ε = 0.3) is larger than that of seventh-order harmonic driven by linearly polarized MIR light (ε = 0). The observed behavior can be reproduced by theoretical calculations that consider different electron temperatures (caused by the THz pulses). Furthermore, the observed stronger suppression of HHG driven by elliptically polarized light reveals the following: in the case of elliptically polarized light, the generation of harmonics via interband transitions to conduction-band states that are closer to the Dirac point is more important than in the case of linearly polarized light. In other words, the quantum pathways via interband transitions to low-energy states are the origin of the enhancement of HHG that can be achieved in graphene by using elliptically polarized light.
Nonlinear Current Injection in Hexagonal Boron Nitride using Linearly Polarized Light in a Deeply Off‐Resonant Regime 査読有り

Wenwen Mao, Angel Rubio, Shunsuke A. Sato

Advanced Optical Materials　12　(22)　2024年6月21日
出版者・発行元： Wiley
DOI： 10.1002/adom.202400651 　

ISSN：2195-1071

eISSN：2195-1071

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Abstract Light‐induced electron dynamics in monolayer hexagonal boron nitride is theoretically investigated under the influence of two‐color linearly‐polarized laser fields at frequencies ω and 2ω, by solving the time‐dependent Schrödinger equation with a tight‐binding model. In the weak field regime, it is confirm that the injection of ballistic current arises from the breakdown of time‐reversal symmetry. This phenomenon is attributed to quantum interference between two distinct excitation paths: a one‐photon (2ℏω) absorption path and a two‐photon (ℏω) absorption path. In a strong field regime, the analysis reveals that the two‐color laser fields may generate a substantial population imbalance within momentum space, consequently facilitating the injection of ballistic current even in a deeply off‐resonant regime. The findings demonstrate that a pronounced population imbalance exceeding 30% of excited electrons can be realized without relying on the ellipticity of the fields. This highlights the potential of linearly polarized light for efficient photovoltaic effects and valley population control in 2D systems and heterostructures.
Limitations of mean-field approximations in describing shift-current and injection-current in materials 査読有り

Shunsuke A. Sato, Angel Rubio

Physical Review B　109　(19)　2024年5月20日
出版者・発行元： American Physical Society (APS)
DOI： 10.1103/physrevb.109.195205 　

ISSN：2469-9950

eISSN：2469-9969

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We theoretically and computationally investigate bulk photovoltaic effects, with a specific focus on shift-current and injection-current. Initially, we perform a numerical analysis of the direct current (dc) induced by a laser pulse with a one-dimensional model, utilizing mean-field theories such as time-dependent Hartree–Fock and time-dependent Hartree methods. Our numerical results, obtained with mean-field theories, reveal that the dc component of the current, as a second-order nonlinear effect, exists even after irradiation with linearly polarized light as a second-order nonlinear effect, indicating the generation of injection-current. Conversely, when we employ the independent-particle approximation, no injection-current is generated by linearly polarized light. To develop the microscopic understanding of injection-current within the mean-field approximation, we further analyze the dc component of the current with the perturbation theory, employing the mean-field approximations, the independent-particle approximation, and the exact solution of the many-body Schrödinger equation. The perturbation analysis clarifies that the injection-current induced by linearly polarized light under the mean-field approximations is an artifact caused by population imbalance, created through quantum interference from unphysical self-excitation pathways. Therefore, investigation of many-body effects on the bulk photovoltaic effects have to be carefully conducted in mean-field schemes due to potential contamination by unphysical dc current. Additionally, we perform the first-principles electron dynamics calculation for BaTiO3 based on the time-dependent density functional theory, and we confirm that the above findings from the one-dimensional model calculation and the perturbation analysis apply to realistic systems. Published by the American Physical Society 2024
High-Order Harmonic Generation in Solids: The Role of Intraband Transitions in Extreme Nonlinear Optics 査読有り

Hideki Hirori, Shunsuke A. Sato, Yoshihiko Kanemitsu

The Journal of Physical Chemistry Letters　15　(8)　2184-2192　2024年2月19日
出版者・発行元： American Chemical Society (ACS)
DOI： 10.1021/acs.jpclett.3c03415 　

ISSN：1948-7185

eISSN：1948-7185
Revealing ultrafast phonon mediated inter-valley scattering through transient absorption and high harmonic spectroscopies 査読有り

Kevin Lively, Shunsuke A. Sato, Guillermo Albareda, Angel Rubio, Aaron Kelly

Physical Review Research　6　(1)　2024年1月19日
出版者・発行元： American Physical Society (APS)
DOI： 10.1103/physrevresearch.6.013069 　

eISSN：2643-1564

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Processes involving ultrafast laser driven electron-phonon dynamics play a fundamental role in the response of quantum systems in a growing number of situations of interest, as evinced by phenomena such as strongly driven phase transitions and light driven engineering of material properties. To show how these processes can be captured from a computational perspective, we simulate the transient absorption spectra and high-harmonic generation signals associated with valley selective excitation and intraband charge-carrier relaxation in monolayer hexagonal boron nitride. We show that the multitrajectory Ehrenfest dynamics approach, implemented in combination with real-time time-dependent density-functional theory and tight-binding models, offers a simple, accurate, and efficient method to study ultrafast electron-phonon coupled phenomena in solids under diverse pump-probe regimes which can be easily incorporated into the majority of real-time software packages. Published by the American Physical Society 2024
Enhancement of high-order harmonic generation in graphene by mid-infrared and terahertz fields 査読有り

Wenwen Mao, Angel Rubio, Shunsuke A. Sato

Physical Review B　109　(4)　2024年1月17日
出版者・発行元： American Physical Society (APS)
DOI： 10.1103/physrevb.109.045421 　

ISSN：2469-9950

eISSN：2469-9969

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We theoretically investigate high-order harmonic generation (HHG) in graphene under mid-infrared (MIR) and terahertz (THz) fields based on a quantum master equation. Numerical simulations show that MIR-induced HHG in graphene can be enhanced by a factor of 10 for fifth harmonic and a factor of 25 for seventh harmonic under a THz field with a peak strength of 0.5 MV/cm by optimizing the relative angle between the MIR and THz fields. To identify the origin of this enhancement, we compare the fully dynamical calculations with a simple thermodynamic model and a nonequilibrium population model. The analysis shows that the enhancement of the high-order harmonics mainly results from a coherent coupling between MIR- and THz-induced transitions that goes beyond a simple THz-induced population contribution. Published by the American Physical Society 2024
Enhancing high harmonic generation in GaAs by elliptically polarized light excitation 査読有り

Fumiya Sekiguchi, Minoru Sakamoto, Kotaro Nakagawa, Hirokazu Tahara, Shunsuke A. Sato, Hideki Hirori, Yoshihiko Kanemitsu

Physical Review B　108　(20)　2023年11月13日
出版者・発行元： American Physical Society (APS)
DOI： 10.1103/physrevb.108.205201 　

ISSN：2469-9950

eISSN：2469-9969
Frequency-resolved Microscopic Current Density Analysis of Linear and Nonlinear Optical Phenomena in Solids 査読有り

Shunsuke A. Sato

Journal of the Physical Society of Japan　92　(9)　2023年9月15日
出版者・発行元： Physical Society of Japan
DOI： 10.7566/jpsj.92.094401 　

ISSN：0031-9015

eISSN：1347-4073
Optimizing Floquet engineering for non-equilibrium steady states with gradient-based methods 査読有り

Alberto Castro, Shunsuke Sato

SciPost Physics　15　(1)　2023年7月26日
出版者・発行元： Stichting SciPost
DOI： 10.21468/scipostphys.15.1.029 　

eISSN：2542-4653

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Non-equilibrium steady states are created when a periodically driven quantum system is also incoherently interacting with an environment - as it is the case in most realistic situations. The notion of Floquet engineering refers to the manipulation of the properties of systems under periodic perturbations. Although it more frequently refers to the coherent states of isolated systems (or to the transient phase for states that are weakly coupled to the environment), it may sometimes be of more interest to consider the final steady states that are reached after decoherence and dissipation take place. In this work, we demonstrate how those final states can be optimally tuned with respect to a given predefined metric, such as for example the maximization of the temporal average value of some observable, by using multicolor periodic perturbations. We show a computational framework that can be used for that purpose, and exemplify the concept using a simple model for the nitrogen-vacancy center in diamond: the goal in this case is to find the driving periodic magnetic field that maximizes a time-averaged spin component. We show that, for example, this technique permits to prepare states whose spin values are forbidden in thermal equilibrium at any temperature.
Gapless detection of broadband terahertz pulses using a metal surface in air based on field-induced second-harmonic generation 査読有り

Shunsuke Tanaka, Yuta Murotani, Shunsuke A. Sato, Tomohiro Fujimoto, Takuya Matsuda, Natsuki Kanda, Ryusuke Matsunaga, Jun Yoshinobu

Applied Physics Letters　122　(25)　2023年6月19日
出版者・発行元： AIP Publishing
DOI： 10.1063/5.0153667 　

ISSN：0003-6951

eISSN：1077-3118

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We investigate second-harmonic generation (SHG) light from a Pt surface in atmosphere under terahertz (THz) pulses. THz pulse-modulated SHG intensity, ΔI2ω, shows a clear time profile of the THz field, which is similar to that of the conventional electro-optic sampling. The result can be explained by interference between THz field-induced second-harmonic light from air molecules in an optical path and a local oscillator from a Pt surface, whereby heterodyne detection of the THz waveform can be achieved. Using numerical calculations of a wave equation, we discuss the contribution of the Gouy phases of all the pulses, including near-infrared, SHG, and THz pulses, and identification of effective nonlinear susceptibility of the Pt surface. Our method, simply using a polished metal surface and air molecules, does not suffer from phonons or phase matching in solid-state optics and does not require any power supply, bias voltage, or fabrication process, but it offers a simple and gapless sampling method for broadband THz pulses. Here, we demonstrate the gapless detection of a broadband THz pulse in the region of 0.2–20 THz using this method.
Floquet-Bloch resonances in near-petahertz electroabsorption spectroscopy of SiO₂ 査読有り

M. Volkov, S. A. Sato, A. Niedermayr, A. Rubio, L. Gallmann, U. Keller

Physical Review B　107　(18)　2023年5月5日
出版者・発行元： American Physical Society (APS)
DOI： 10.1103/physrevb.107.184304 　

ISSN：2469-9950

eISSN：2469-9969
Ultrafast electron localization and screening in a transition metal dichalcogenide 査読有り

Z. Schumacher, S. A. Sato, S. Neb, A. Niedermayr, L. Gallmann, A. Rubio, U. Keller

Proceedings of the National Academy of Sciences　120　(15)　2023年4月4日
出版者・発行元： Proceedings of the National Academy of Sciences
DOI： 10.1073/pnas.2221725120 　

ISSN：0027-8424

eISSN：1091-6490

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The coupling of light to electrical charge carriers in semiconductors is the foundation of many technological applications. Attosecond transient absorption spectroscopy measures simultaneously how excited electrons and the vacancies they leave behind dynamically react to the applied optical fields. In compound semiconductors, these dynamics can be probed via any of their atomic constituents with core-level transitions into valence and conduction band. Typically, the atomic species forming the compound contribute comparably to the relevant electronic properties of the material. One therefore expects to observe similar dynamics, irrespective of the choice of atomic species via which it is probed. Here, we show in the two-dimensional transition metal dichalcogenide semiconductor MoSe ₂ , that through a selenium-based core-level transition we observe charge carriers acting independently from each other, while when probed through molybdenum, the collective, many-body motion of the carriers dominates. Such unexpectedly contrasting behavior can be explained by a strong localization of electrons around molybdenum atoms following absorption of light, which modifies the local fields acting on the carriers. We show that similar behavior in elemental titanium metal [M. Volkov et al. , Nat. Phys. 15 , 1145–1149 (2019)] carries over to transition metal-containing compounds and is expected to play an essential role for a wide range of such materials. Knowledge of independent particle and collective response is essential for fully understanding these materials.
Floquet band engineering in action 査読有り

Hannes Hübener, Umberto De Giovannini, Shunsuke A. Sato, Angel Rubio

Science Bulletin　68　(8)　751-752　2023年4月
出版者・発行元： Elsevier BV
DOI： 10.1016/j.scib.2023.03.046 　

ISSN：2095-9273
Floquet engineering with quantum optimal control theory 査読有り

Alberto Castro, Umberto De Giovannini, Shunsuke A Sato, Hannes Hübener, Angel Rubio

New Journal of Physics　25　(4)　043023-043023　2023年4月1日
出版者・発行元： IOP Publishing
DOI： 10.1088/1367-2630/accb05 　

eISSN：1367-2630

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Abstract Floquet engineering consists in the modification of physical systems by the application of periodic time-dependent perturbations. The search for the shape of the periodic perturbation that best modifies the properties of a system in order to achieve some predefined metastable target behavior can be formulated as an optimal control problem. We discuss several ways to formulate and solve this problem. We present, as examples, some applications in the context of material science, although the methods discussed here are valid for any quantum system (from molecules and nanostructures to extended periodic and non periodic quantum materials). In particular, we show how one can achieve the manipulation of the Floquet pseudo-bandstructure of a transition metal dichalcogenide monolayer (MoS₂).
Second harmonic Hall responses of insulators as a probe of Berry curvature dipole 査読有り

Mahmut Sait Okyay, Shunsuke A. Sato, Kun Woo Kim, Binghai Yan, Hosub Jin, Noejung Park

Communications Physics　5　(1)　2022年11月26日
出版者・発行元： Springer Science and Business Media LLC
DOI： 10.1038/s42005-022-01086-9 　

eISSN：2399-3650

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Abstract Diverse nonlinear optical responses of metallic band states have been characterized in terms of the Berry curvature dipole (BCD) or other multipole structures of Berry curvature. Here, we find that the second harmonic optical responses of insulators to sub-bandgap light are also delicately associated with the interband BCD. We performed real-time time-dependent density functional theory calculations and theoretically analyzed the second harmonic generation susceptibility tensors. The two-band term of the second-order susceptibility is precisely proportional to the interband BCD, which is particularly significant for low-symmetric systems with a small bandgap. We show that higher-order responses to nonperturbative strong fields can be associated with higher poles of Berry curvature. We suggest that the consequences of symmetry lowering can be detected by nonlinear optical responses through adjustments of the dipole or other multipole structures of the Berry curvature texture.
Controlling Floquet states on ultrashort time scales 査読有り

Matteo Lucchini, Fabio Medeghini, Yingxuan Wu, Federico Vismarra, Rocío Borrego-Varillas, Aurora Crego, Fabio Frassetto, Luca Poletto, Shunsuke A. Sato, Hannes Hübener, Umberto De Giovannini, Ángel Rubio, Mauro Nisoli

Nature Communications　13　(1)　2022年11月19日
出版者・発行元： Springer Science and Business Media LLC
DOI： 10.1038/s41467-022-34973-4 　

eISSN：2041-1723

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Abstract The advent of ultrafast laser science offers the unique opportunity to combine Floquet engineering with extreme time resolution, further pushing the optical control of matter into the petahertz domain. However, what is the shortest driving pulse for which Floquet states can be realised remains an unsolved matter, thus limiting the application of Floquet theory to pulses composed by many optical cycles. Here we ionized Ne atoms with few-femtosecond pulses of selected time duration and show that a Floquet state can be observed already with a driving field that lasts for only 10 cycles. For shorter pulses, down to 2 cycles, the finite lifetime of the driven state can still be explained using an analytical model based on Floquet theory. By demonstrating that the amplitude and number of Floquet-like sidebands in the photoelectron spectrum can be controlled not only with the driving laser pulse intensity and frequency, but also by its duration, our results add a new lever to the toolbox of Floquet engineering.
Simulating Terahertz Field-Induced Ferroelectricity in Quantum Paraelectric SrTiO₃ 査読有り

Dongbin Shin, Simone Latini, Christian Schäfer, Shunsuke A. Sato, Edoardo Baldini, Umberto De Giovannini, Hannes Hübener, Angel Rubio

Physical Review Letters　129　(16)　2022年10月10日
出版者・発行元： American Physical Society (APS)
DOI： 10.1103/physrevlett.129.167401 　

ISSN：0031-9007

eISSN：1079-7114
Charge transfer in ultrafast isomerization of acetylene ions 査読有り

Wan-Dong Yu, Hao Liang, Cong-Zhang Gao, Shunsuke A. Sato, Bao-Ren Wei, Alberto Castro, Angel Rubio, Liang-You Peng

Physical Review A　106　(3)　2022年9月20日
出版者・発行元： American Physical Society (APS)
DOI： 10.1103/physreva.106.033111 　

ISSN：2469-9926

eISSN：2469-9934
Floquet engineering the band structure of materials with optimal control theory 査読有り

Alberto Castro, Umberto De Giovannini, Shunsuke A. Sato, Hannes Hübener, Angel Rubio

Physical Review Research　4　(3)　2022年9月19日
出版者・発行元： American Physical Society (APS)
DOI： 10.1103/physrevresearch.4.033213 　

eISSN：2643-1564
Time- and angle-resolved photoelectron spectroscopy of strong-field light-dressed solids: Prevalence of the adiabatic band picture 査読有り

Ofer Neufeld, Wenwen Mao, Hannes Hübener, Nicolas Tancogne-Dejean, Shunsuke A. Sato, Umberto De Giovannini, Angel Rubio

Physical Review Research　4　(3)　2022年8月4日
出版者・発行元： American Physical Society (APS)
DOI： 10.1103/physrevresearch.4.033101 　

eISSN：2643-1564
Terahertz-induced high-order harmonic generation and nonlinear charge transport in graphene 査読有り

Wenwen Mao, Angel Rubio, Shunsuke A. Sato

Physical Review B　106　(2)　2022年7月29日
出版者・発行元： American Physical Society (APS)
DOI： 10.1103/physrevb.106.024313 　

ISSN：2469-9950

eISSN：2469-9969
Size-controlled quantum dots reveal the impact of intraband transitions on high-order harmonic generation in solids 査読有り

Kotaro Nakagawa, Hideki Hirori, Shunsuke A. Sato, Hirokazu Tahara, Fumiya Sekiguchi, Go Yumoto, Masaki Saruyama, Ryota Sato, Toshiharu Teranishi, Yoshihiko Kanemitsu

Nature Physics　18　(8)　874-878　2022年6月23日
出版者・発行元： Springer Science and Business Media LLC
DOI： 10.1038/s41567-022-01639-3 　

ISSN：1745-2473

eISSN：1745-2481
Few-Femtosecond Dynamics of Free-Free Opacity in Optically Heated Metals 査読有り

A. Niedermayr, M. Volkov, S. A. Sato, N. Hartmann, Z. Schumacher, S. Neb, A. Rubio, L. Gallmann, U. Keller

Physical Review X　12　(2)　2022年5月25日
出版者・発行元： American Physical Society (APS)
DOI： 10.1103/physrevx.12.021045 　

eISSN：2160-3308
Reconstruction of ultrafast exciton dynamics with a phase-retrieval algorithm 査読有り

Gian Luca Dolso, Bruno Moio, Giacomo Inzani, Nicola Di Palo, Shunsuke A. Sato, Rocío Borrego-Varillas, Mauro Nisoli, Matteo Lucchini

Optics Express　30　(8)　12248-12248　2022年3月28日
出版者・発行元： Optica Publishing Group
DOI： 10.1364/oe.451759 　

eISSN：1094-4087

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The first step to gain optical control over the ultrafast processes initiated by light in solids is a correct identification of the physical mechanisms at play. Among them, exciton formation has been identified as a crucial phenomenon which deeply affects the electro-optical properties of most semiconductors and insulators of technological interest. While recent experiments based on attosecond spectroscopy techniques have demonstrated the possibility to observe the early-stage exciton dynamics, the description of the underlying exciton properties remains non-trivial. In this work we propose a new method called extended Ptychographic Iterative engine for eXcitons (ePIX), capable of reconstructing the main physical properties which determine the evolution of the quasi-particle with no prior knowledge of the exact relaxation dynamics or the pump temporal characteristics. By demonstrating its accuracy even when the exciton dynamics is comparable to the pump pulse duration, ePIX is established as a powerful approach to widen our knowledge of solid-state physics.
First-principles calculations for transient absorption of laser-excited magnetic materials 査読有り

Shunsuke A Sato

Electronic Structure　4　(1)　014007-014007　2022年2月28日
出版者・発行元： IOP Publishing
DOI： 10.1088/2516-1075/ac52df 　

eISSN：2516-1075

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Abstract We investigate the modification in the optical properties of laser-excited bulk cobalt and nickel using the time-dependent density functional theory at a finite electron temperature. As a result of the first-principles simulation, a complex change in the photoabsorption of the magnetic materials is observed around the M _2,3 absorption edge. Based on the microscopic analysis, we clarify that this complex absorption change consists of the two following components: (i) the decrease in the photoabsorption in a narrow energy range around the M _2,3 edge, which reflects the blue shift of the absorption edge due to the light-induced demagnetization, and (ii) the increase in the photoabsorption in a wider range around the M _2,3 edge, which reflects the modification in the local-field effect due to the light-induced electron localization. The relation between the transient optical and magnetic properties may open a way to monitor ultrafast (de)magnetization and spin dynamics in magnetic materials via transient absorption spectroscopy.
First-principles modelling for time-resolved ARPES under different pump–probe conditions 査読有り

Umberto De Giovannini, Shunsuke A. Sato, Hannes Hübener, Angel Rubio

Journal of Electron Spectroscopy and Related Phenomena　254　147152-147152　2022年1月
出版者・発行元： Elsevier BV
DOI： 10.1016/j.elspec.2021.147152 　

ISSN：0368-2048
Two-step Brillouin zone sampling for efficient computation of electron dynamics in solids 査読有り

Shunsuke A Sato

Journal of Physics: Condensed Matter　34　(9)　095903-095903　2021年12月16日
出版者・発行元： IOP Publishing
DOI： 10.1088/1361-648x/ac3f00 　

ISSN：0953-8984

eISSN：1361-648X

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Abstract We develop a numerical Brillouin-zone integration scheme for real-time propagation of electronic systems with time-dependent density functional theory. This scheme is based on the decomposition of a large simulation into a set of small independent simulations. The performance of the decomposition scheme is examined in both linear and nonlinear regimes by computing the linear optical properties of bulk silicon and high-order harmonic generation. The decomposition of a large simulation into a set of independent simulations can improve the efficiency of parallel computation by reducing communication and synchronization overhead and enhancing the portability of simulations across a relatively small cluster machine.
Conditional Wave Function Theory: A Unified Treatment of Molecular Structure and Nonadiabatic Dynamics 査読有り

Guillermo Albareda, Kevin Lively, Shunsuke A. Sato, Aaron Kelly, Angel Rubio

Journal of Chemical Theory and Computation　17　(12)　7321-7340　2021年11月9日
出版者・発行元： American Chemical Society (ACS)
DOI： 10.1021/acs.jctc.1c00772 　

ISSN：1549-9618

eISSN：1549-9626
Quantum paraelectric phase of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>SrTiO</mml:mi><mml:mn>3</mml:mn></mml:msub></mml:math> from first principles 査読有り

Dongbin Shin, Simone Latini, Christian Schäfer, Shunsuke A. Sato, Umberto De Giovannini, Hannes Hübener, Angel Rubio

Physical Review B　104　(6)　2021年8月10日
出版者・発行元： American Physical Society (APS)
DOI： 10.1103/physrevb.104.l060103 　

ISSN：2469-9950

eISSN：2469-9969
The ferroelectric photo ground state of SrTiO ₃ : Cavity materials engineering 査読有り

Simone Latini, Dongbin Shin, Shunsuke A. Sato, Christian Schäfer, Umberto De Giovannini, Hannes Hübener, Angel Rubio

Proceedings of the National Academy of Sciences　118　(31)　2021年7月27日
出版者・発行元： Proceedings of the National Academy of Sciences
DOI： 10.1073/pnas.2105618118 　

ISSN：0027-8424

eISSN：1091-6490

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Significance Controlling collective phenomena in quantum materials is a promising route toward engineering material properties on demand. Strong THz lasers have been successful at inducing ferroelectricity in . Here we demonstrate, from atomistic calculations, that cavity quantum vacuum fluctuations induce a change in the collective phase of in the strong light–matter coupling regime. Under these conditions, the ferroelectric phase is stabilized as the ground state, instead of the quantum paraelectric one. We conceptualize this light–matter hybrid state as a material photo ground state: Fundamental properties such as crystal structure, phonon frequencies, and the collective phase of a material are determined by the quantum light–matter coupling in equilibrium conditions. Cavity-coupling adds a new dimension to the phase diagram of .
Survival of Floquet–Bloch States in the Presence of Scattering 査読有り

Sven Aeschlimann, Shunsuke A. Sato, Razvan Krause, Mariana Chávez-Cervantes, Umberto De Giovannini, Hannes Hübener, Stiven Forti, Camilla Coletti, Kerstin Hanff, Kai Rossnagel, Angel Rubio, Isabella Gierz

Nano Letters　21　(12)　5028-5035　2021年6月4日
出版者・発行元： American Chemical Society (ACS)
DOI： 10.1021/acs.nanolett.1c00801 　

ISSN：1530-6984

eISSN：1530-6992
Nonlinear electric conductivity and THz-induced charge transport in graphene 査読有り

Shunsuke A Sato, Angel Rubio

New Journal of Physics　23　(6)　063047-063047　2021年6月1日
出版者・発行元： IOP Publishing
DOI： 10.1088/1367-2630/ac03d0 　

eISSN：1367-2630

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Abstract Based on the quantum master equation approach, the nonlinear electric conductivity of graphene is investigated under static electric fields for various chemical potential shifts. The simulation results show that, as the field strength increases, the effective conductivity is firstly suppressed, reflecting the depletion of effective carriers due to the large displacement in the Brillouin zone caused by the strong field. Then, as the field strength exceeds 1 MV m⁻¹, the effective conductivity increases, overcoming the carrier depletion via the Landau–Zener tunneling process. Based on the nonlinear behavior of the conductivity, the charge transport induced by few-cycle THz pulses is studied to elucidate the ultrafast control of electric current in matter.
First-principles calculations for attosecond electron dynamics in solids 査読有り

Shunsuke A. Sato

Computational Materials Science　194　110274-110274　2021年6月
出版者・発行元： Elsevier BV
DOI： 10.1016/j.commatsci.2020.110274 　

ISSN：0927-0256
Simulating Vibronic Spectra without Born–Oppenheimer Surfaces 査読有り

Kevin Lively, Guillermo Albareda, Shunsuke A. Sato, Aaron Kelly, Angel Rubio

The Journal of Physical Chemistry Letters　12　(12)　3074-3081　2021年3月22日
出版者・発行元： American Chemical Society (ACS)
DOI： 10.1021/acs.jpclett.1c00073 　

ISSN：1948-7185

eISSN：1948-7185
Single and double charge transfer in the Ne²⁺+He collision within time-dependent density-functional theory 査読有り

Wandong Yu, Cong-Zhang Gao, Shunsuke A. Sato, Alberto Castro, Angel Rubio, Baoren Wei

Physical Review A　103　(3)　2021年3月12日
出版者・発行元： American Physical Society (APS)
DOI： 10.1103/physreva.103.032816 　

ISSN：2469-9926

eISSN：2469-9934
Unravelling the intertwined atomic and bulk nature of localised excitons by attosecond spectroscopy 査読有り

Matteo Lucchini, Shunsuke A. Sato, Giacinto D. Lucarelli, Bruno Moio, Giacomo Inzani, Rocío Borrego-Varillas, Fabio Frassetto, Luca Poletto, Hannes Hübener, Umberto De Giovannini, Angel Rubio, Mauro Nisoli

Nature Communications　12　(1)　2021年2月15日
出版者・発行元： Springer Science and Business Media LLC
DOI： 10.1038/s41467-021-21345-7 　

eISSN：2041-1723

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Abstract The electro-optical properties of most semiconductors and insulators of technological interest are dominated by the presence of electron-hole quasi-particles, called excitons. The manipulation of excitons in dielectrics has recently received great attention, with possible applications in different fields including optoelectronics and photonics. Here, we apply attosecond transient reflection spectroscopy in a sequential two-foci geometry and observe sub-femtosecond dynamics of a core-level exciton in bulk MgF₂ single crystals. Furthermore, we access absolute phase delays, which allow for an unambiguous comparison with theoretical calculations. Our results show that excitons surprisingly exhibit a dual atomic- and solid-like character, which manifests itself on different time scales. While the former is responsible for a femtosecond optical Stark effect, the latter dominates the attosecond excitonic response. Further theoretical investigation reveals a link with the exciton sub-femtosecond nanometric motion and allows us to envision a new route to control exciton dynamics in the close-to-petahertz regime.
High-order harmonic generation in graphene: Nonlinear coupling of intraband and interband transitions 査読有り

Shunsuke A. Sato, Hideki Hirori, Yasuyuki Sanari, Yoshihiko Kanemitsu, Angel Rubio

Physical Review B　103　(4)　2021年1月29日
出版者・発行元： American Physical Society (APS)
DOI： 10.1103/physrevb.103.l041408 　

ISSN：2469-9950

eISSN：2469-9969
Floquet dynamics in light-driven solids 査読有り

M. Nuske, L. Broers, B. Schulte, G. Jotzu, S. A. Sato, A. Cavalleri, A. Rubio, J. W. McIver, L. Mathey

Physical Review Research　2　(4)　2020年12月22日
出版者・発行元： American Physical Society (APS)
DOI： 10.1103/physrevresearch.2.043408 　

eISSN：2643-1564
Dynamical amplification of electric polarization through nonlinear phononics in 2D SnTe 査読有り

Dongbin Shin, Shunsuke A. Sato, Hannes Hübener, Umberto De Giovannini, Noejung Park, Angel Rubio

npj Computational Materials　6　(1)　2020年11月30日
出版者・発行元： Springer Science and Business Media LLC
DOI： 10.1038/s41524-020-00449-6 　

eISSN：2057-3960

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Abstract Ultrafast optical control of ferroelectricity using intense terahertz fields has attracted significant interest. Here we show that the nonlinear interactions between two optical phonons in SnTe, a two-dimensional in-plane ferroelectric material, enables a dynamical amplification of the electric polarization within subpicoseconds time domain. Our first-principles time-dependent simulations show that the infrared-active out-of-plane phonon mode, pumped to nonlinear regimes, spontaneously generates in-plane motions, leading to rectified oscillations in the in-plane electric polarization. We suggest that this dynamical control of ferroelectric material, by nonlinear phonon excitation, can be utilized to achieve ultrafast control of the photovoltaic or other nonlinear optical responses.
Floquet states in dissipative open quantum systems 査読有り

S A Sato, U De Giovannini, S Aeschlimann, I Gierz, H Hübener, A Rubio

Journal of Physics B: Atomic, Molecular and Optical Physics　53　(22)　225601-225601　2020年10月22日
出版者・発行元： IOP Publishing
DOI： 10.1088/1361-6455/abb127 　

ISSN：0953-4075

eISSN：1361-6455

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Abstract We theoretically investigate basic properties of nonequilibrium steady states of periodically-driven open quantum systems based on the full solution of the Maxwell–Bloch equation. In a resonant driving condition, we find that the transverse relaxation, also known as decoherence, significantly destructs the formation of Floquet states while the longitudinal relaxation does not directly affect it. Furthermore, by evaluating the quasienergy spectrum of the nonequilibrium steady states, we demonstrate that Rabi splitting can be observed as long as the decoherence time is as short as one third of the Rabi-cycle. Moreover, we find that Floquet states can be formed even under significant dissipation when the decoherence time is substantially shorter than the cycle of driving, once the driving field strength becomes strong enough. In an off-resonant condition, we demonstrate that the Floquet states can be realized even in weak field regimes because the system is not excited and the decoherence mechanism is not activated. Once the field strength becomes strong enough, the system can be excited by multi-photon absorption and the decoherence process becomes active. As a result, the Floquet states are significantly disturbed by the environment even in the off-resonant condition. Thus, we show here that the suppression of energy transfer from light to matter is a key condition for the realization of Floquet states in both on- and off-resonant conditions not only because it prevents material damage but also because it contributes to preserving coherence.
Direct Measurement of Electron-Phonon Coupling with Time-Resolved ARPES 査読有り

Umberto De Giovannini, Hannes Hübener, Shunsuke A. Sato, Angel Rubio

Physical Review Letters　125　(13)　2020年9月21日
出版者・発行元： American Physical Society (APS)
DOI： 10.1103/physrevlett.125.136401 　

ISSN：0031-9007

eISSN：1079-7114
Role of electron scattering on the high-order harmonic generation from solids 査読有り

Chang-Ming Wang, Nicolas Tancogne-Dejean, Massimo Altarelli, Angel Rubio, Shunsuke A. Sato

Physical Review Research　2　(3)　2020年8月28日
出版者・発行元： American Physical Society (APS)
DOI： 10.1103/physrevresearch.2.033333 　

eISSN：2643-1564
Role of virtual band population for high harmonic generation in solids 査読有り

Yasuyuki Sanari, Hideki Hirori, Tomoko Aharen, Hirokazu Tahara, Yasushi Shinohara, Kenichi L. Ishikawa, Tomohito Otobe, Peiyu Xia, Nobuhisa Ishii, Jiro Itatani, Shunsuke A. Sato, Yoshihiko Kanemitsu

Physical Review B　102　(4)　2020年7月30日
出版者・発行元： American Physical Society (APS)
DOI： 10.1103/physrevb.102.041125 　

ISSN：2469-9950

eISSN：2469-9969
Room Temperature Terahertz Electroabsorption Modulation by Excitons in Monolayer Transition Metal Dichalcogenides 査読有り

Jiaojian Shi, Edoardo Baldini, Simone Latini, Shunsuke A. Sato, Yaqing Zhang, Brandt C. Pein, Pin-Chun Shen, Jing Kong, Angel Rubio, Nuh Gedik, Keith A. Nelson

Nano Letters　20　(7)　5214-5220　2020年6月15日
出版者・発行元： American Chemical Society (ACS)
DOI： 10.1021/acs.nanolett.0c01134 　

ISSN：1530-6984

eISSN：1530-6992
Octopus, a computational framework for exploring light-driven phenomena and quantum dynamics in extended and finite systems 査読有り

Nicolas Tancogne-Dejean, Micael J. T. Oliveira, Xavier Andrade, Heiko Appel, Carlos H. Borca, Guillaume Le Breton, Florian Buchholz, Alberto Castro, Stefano Corni, Alfredo A. Correa, Umberto De Giovannini, Alain Delgado, Florian G. Eich, Johannes Flick, Gabriel Gil, Adrián Gomez, Nicole Helbig, Hannes Hübener, René Jestädt, Joaquim Jornet-Somoza, Ask H. Larsen, Irina V. Lebedeva, Martin Lüders, Miguel A. L. Marques, Sebastian T. Ohlmann, Silvio Pipolo, Markus Rampp, Carlo A. Rozzi, David A. Strubbe, Shunsuke A. Sato, Christian Schäfer, Iris Theophilou, Alicia Welden, Angel Rubio

The Journal of Chemical Physics　152　(12)　2020年3月31日
出版者・発行元： AIP Publishing
DOI： 10.1063/1.5142502 　

ISSN：0021-9606

eISSN：1089-7690

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Over the last few years, extraordinary advances in experimental and theoretical tools have allowed us to monitor and control matter at short time and atomic scales with a high degree of precision. An appealing and challenging route toward engineering materials with tailored properties is to find ways to design or selectively manipulate materials, especially at the quantum level. To this end, having a state-of-the-art ab initio computer simulation tool that enables a reliable and accurate simulation of light-induced changes in the physical and chemical properties of complex systems is of utmost importance. The first principles real-space-based Octopus project was born with that idea in mind, i.e., to provide a unique framework that allows us to describe non-equilibrium phenomena in molecular complexes, low dimensional materials, and extended systems by accounting for electronic, ionic, and photon quantum mechanical effects within a generalized time-dependent density functional theory. This article aims to present the new features that have been implemented over the last few years, including technical developments related to performance and massive parallelism. We also describe the major theoretical developments to address ultrafast light-driven processes, such as the new theoretical framework of quantum electrodynamics density-functional formalism for the description of novel light–matter hybrid states. Those advances, and others being released soon as part of the Octopus package, will allow the scientific community to simulate and characterize spatial and time-resolved spectroscopies, ultrafast phenomena in molecules and materials, and new emergent states of matter (quantum electrodynamical-materials).
Attosecond timing of the dynamical Franz–Keldysh effect 査読有り

M Lucchini, S A Sato, F Schlaepfer, K Yabana, L Gallmann, A Rubio, U Keller

Journal of Physics: Photonics　2　(2)　025001-025001　2020年2月18日
出版者・発行元： IOP Publishing
DOI： 10.1088/2515-7647/ab70cb 　

eISSN：2515-7647

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Abstract To what extent do intra- or inter-band transitions dominate the optical response of dielectrics when pumped by a few-cycle near-infrared transient electric field? In order to find an answer to this question we investigate the dynamical Franz–Keldysh effect in polycrystalline diamond and discuss in detail the attosecond delay of the induced electron dynamics with regard to the driving transient electric field while the peak intensity is varied between 1 × 10¹² and 10 × 10¹² W cm⁻². We found that the main oscillating feature in transient absorption at 43 eV is in phase with the electric field of the pump, to within 49 ± 78 as. However, the phase delay shows a slightly asymmetric V-shaped linear energy dispersion with a rate of about 200 as eV^–1. Theoretical calculations within the dipole approximation reproduce the data and allow us to conclude that intra-band motion dominates under our experimental conditions.
Exact exchange-correlation potential of effectively interacting Kohn-Sham systems 査読有り

Shunsuke A. Sato, Angel Rubio

Physical Review A　101　(1)　2020年1月15日
出版者・発行元： American Physical Society (APS)
DOI： 10.1103/physreva.101.012510 　

ISSN：2469-9926

eISSN：2469-9934
Photovoltaic Effect from the Viewpoint of Time-reversal Symmetry 査読有り

Shunsuke A. Sato

Journal of the Physical Society of Japan　88　(11)　115003-115003　2019年11月15日
出版者・発行元： Physical Society of Japan
DOI： 10.7566/jpsj.88.115003 　

ISSN：0031-9015

eISSN：1347-4073
Light-induced anomalous Hall effect in massless Dirac fermion systems and topological insulators with dissipation 査読有り

S A Sato, P Tang, M A Sentef, U De Giovannini, H Hübener, A Rubio

New Journal of Physics　21　(9)　093005-093005　2019年9月1日
出版者・発行元： IOP Publishing
DOI： 10.1088/1367-2630/ab3acf 　

eISSN：1367-2630
Attosecond screening dynamics mediated by electron localization in transition metals 査読有り

M. Volkov, S. A. Sato, F. Schlaepfer, L. Kasmi, N. Hartmann, M. Lucchini, L. Gallmann, A. Rubio, U. Keller

Nature Physics　15　(11)　1145-1149　2019年8月5日
出版者・発行元： Springer Science and Business Media LLC
DOI： 10.1038/s41567-019-0602-9 　

ISSN：1745-2473

eISSN：1745-2481
Charge Density Wave Melting in One-Dimensional Wires with Femtosecond Subgap Excitation 査読有り

M. Chávez-Cervantes, G. E. Topp, S. Aeschlimann, R. Krause, S. A. Sato, M. A. Sentef, I. Gierz

Physical Review Letters　123　(3)　2019年7月19日
出版者・発行元： American Physical Society (APS)
DOI： 10.1103/physrevlett.123.036405 　

ISSN：0031-9007

eISSN：1079-7114
Microscopic theory for the light-induced anomalous Hall effect in graphene 査読有り

S. A. Sato, J. W. McIver, M. Nuske, P. Tang, G. Jotzu, B. Schulte, H. Hübener, U. De Giovannini, L. Mathey, M. A. Sentef, A. Cavalleri, A. Rubio

Physical Review B　99　(21)　2019年6月10日
出版者・発行元： American Physical Society (APS)
DOI： 10.1103/physrevb.99.214302 　

ISSN：2469-9950

eISSN：2469-9969
Nonlinear polarization evolution using time-dependent density functional theory 査読有り

Mitsuharu Uemoto, Yuki Kuwabara, Shunsuke A. Sato, Kazuhiro Yabana

The Journal of Chemical Physics　150　(9)　2019年3月1日
出版者・発行元： AIP Publishing
DOI： 10.1063/1.5068711 　

ISSN：0021-9606

eISSN：1089-7690

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We propose a theoretical and computational approach to investigate temporal behavior of a nonlinear polarization in a perturbative regime induced by an intense and ultrashort pulsed electric field. First-principles time-dependent density functional theory is employed to describe the electron dynamics. Temporal evolution of third-order nonlinear polarization is extracted from a few calculations of electron dynamics induced by pulsed electric fields with the same time profile but different amplitudes. We discuss characteristic features of the nonlinear polarization evolution as well as an extraction of nonlinear susceptibilities and time delays by fitting the polarization. We also carry out a decomposition of temporal and spatial changes in the electron density in power series with respect to the field amplitude. It helps to get insight into the origin of the nonlinear polarization in atomic scale.
Theory for Electron Excitation in Dielectrics under an Intense Linear and Circularly Polarized Laser Fields 査読有り

Tomohito Otobe, Yasushi Shinohara, Shunsuke A. Sato, Kazuhiro Yabana

Journal of the Physical Society of Japan　88　(2)　024706-024706　2019年2月15日
出版者・発行元： Physical Society of Japan
DOI： 10.7566/jpsj.88.024706 　

ISSN：0031-9015

eISSN：1347-4073
Unraveling materials Berry curvature and Chern numbers from real-time evolution of Bloch states 査読有り

Dongbin Shin, Shunsuke A. Sato, Hannes Hübener, Umberto De Giovannini, Jeongwoo Kim, Noejung Park, Angel Rubio

Proceedings of the National Academy of Sciences　116　(10)　4135-4140　2019年2月14日
出版者・発行元： Proceedings of the National Academy of Sciences
DOI： 10.1073/pnas.1816904116 　

ISSN：0027-8424

eISSN：1091-6490

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Significance It was established by Thouless, Kohmoto, Nightingale, and den Nijs in 1982 that the topology of the solid-state wavefunctions leads to quantization of transverse electrical conductivity of an insulator. This recognition has led to the development of the new field of topological materials characterized by symmetry-protected quantum numbers. Here, we propose a general and computationally efficient framework enabling one to unveil and predict materials-topological invariants in terms of physical observables, such as the bulk time-dependent current. We show how the quantized charge and spin Hall effect appears even for materials with a non-Abelian Berry phase. This dynamical approach is not necessarily restricted to density functional theory, but can be extended to other schemes and to other methods dealing with correlations explicitly.
SALMON: Scalable Ab-initio Light–Matter simulator for Optics and Nanoscience 査読有り

Masashi Noda, Shunsuke A. Sato, Yuta Hirokawa, Mitsuharu Uemoto, Takashi Takeuchi, Shunsuke Yamada, Atsushi Yamada, Yasushi Shinohara, Maiku Yamaguchi, Kenji Iida, Isabella Floss, Tomohito Otobe, Kyung-Min Lee, Kazuya Ishimura, Taisuke Boku, George F. Bertsch, Katsuyuki Nobusada, Kazuhiro Yabana

Computer Physics Communications　235　356-365　2019年2月
出版者・発行元： Elsevier BV
DOI： 10.1016/j.cpc.2018.09.018 　

ISSN：0010-4655
Ab Initio Simulation of Attosecond Transient Absorption Spectroscopy in Two-Dimensional Materials 査読有り

Shunsuke A. Sato, Hannes Hübener, Umberto De Giovannini, Angel Rubio

Applied Sciences　8　(10)　1777-1777　2018年9月30日
出版者・発行元： MDPI AG
DOI： 10.3390/app8101777 　

eISSN：2076-3417

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We extend the first-principles analysis of attosecond transient absorption spectroscopy to two-dimensional materials. As an example of two-dimensional materials, we apply the analysis to monolayer hexagonal boron nitride (h-BN) and compute its transient optical properties under intense few-cycle infrared laser pulses. Nonadiabatic features are observed in the computed transient absorption spectra. To elucidate the microscopic origin of these features, we analyze the electronic structure of h-BN with density functional theory and investigate the dynamics of specific energy bands with a simple two-band model. Finally, we find that laser-induced intraband transitions play a significant role in the transient absorption even for the two-dimensional material and that the nonadiabatic features are induced by the dynamical Franz–Keldysh effect with an anomalous band dispersion.
Role of intraband transitions in photocarrier generation 査読有り

Shunsuke A. Sato, Matteo Lucchini, Mikhail Volkov, Fabian Schlaepfer, Lukas Gallmann, Ursula Keller, Angel Rubio

Physical Review B　98　(3)　2018年7月5日
出版者・発行元： American Physical Society (APS)
DOI： 10.1103/physrevb.98.035202 　

ISSN：2469-9950

eISSN：2469-9969
First-principles simulations for attosecond photoelectron spectroscopy based on time-dependent density functional theory 査読有り

Shunsuke A. Sato, Hannes Hübener, Angel Rubio, Umberto De Giovannini

The European Physical Journal B　91　(6)　2018年6月22日
出版者・発行元： Springer Science and Business Media LLC
DOI： 10.1140/epjb/e2018-90108-7 　

ISSN：1434-6028

eISSN：1434-6036
Performance Optimization and Evaluation of Scalable Optoelectronics Application on Large Scale KNL Cluster 査読有り

Yuta Hirokawa, Taisuke Boku, Mitsuharu Uemoto, Shunsuke A. Sato, Kazuhiro Yabana

Lecture Notes in Computer Science　205-225　2018年5月29日
出版者・発行元： Springer International Publishing
DOI： 10.1007/978-3-319-92040-5_11 　

ISSN：0302-9743

eISSN：1611-3349
Velocity-gauge real-time TDDFT within a numerical atomic orbital basis set 査読有り

C.D. Pemmaraju, F.D. Vila, J.J. Kas, S.A. Sato, J.J. Rehr, K. Yabana, David Prendergast

Computer Physics Communications　226　30-38　2018年5月
出版者・発行元： Elsevier BV
DOI： 10.1016/j.cpc.2018.01.013 　

ISSN：0010-4655
Coupled forward-backward trajectory approach for nonequilibrium electron-ion dynamics 査読有り

Shunsuke A. Sato, Aaron Kelly, Angel Rubio

Physical Review B　97　(13)　2018年4月25日
出版者・発行元： American Physical Society (APS)
DOI： 10.1103/physrevb.97.134308 　

ISSN：2469-9950

eISSN：2469-9969
Attosecond optical-field-enhanced carrier injection into the GaAs conduction band 査読有り

F. Schlaepfer, M. Lucchini, S. A. Sato, M. Volkov, L. Kasmi, N. Hartmann, A. Rubio, L. Gallmann, U. Keller

Nature Physics　14　(6)　560-564　2018年3月12日
出版者・発行元： Springer Science and Business Media LLC
DOI： 10.1038/s41567-018-0069-0 　

ISSN：1745-2473

eISSN：1745-2481
Performance Evaluation of Large Scale Electron Dynamics Simulation under Many-core Cluster based on Knights Landing 査読有り

Yuta Hirokawa, Taisuke Boku, Shunsuke A. Sato, Kazuhiro Yabana

Proceedings of the International Conference on High Performance Computing in Asia-Pacific Region　183-191　2018年1月28日
出版者・発行元： ACM
DOI： 10.1145/3149457.3149465 　
Ab initio multiscale simulation of high-order harmonic generation in solids 査読有り

Isabella Floss, Christoph Lemell, Georg Wachter, Valerie Smejkal, Shunsuke A. Sato, Xiao-Min Tong, Kazuhiro Yabana, Joachim Burgdörfer

Physical Review A　97　(1)　2018年1月16日
出版者・発行元： American Physical Society (APS)
DOI： 10.1103/physreva.97.011401 　

ISSN：2469-9926

eISSN：2469-9934
First-principles calculations for initial electronic excitation in dielectrics induced by intense femtosecond laser pulses 査読有り

Shunsuke A. Sato, Kazuhiro Yabana

SPIE Proceedings　10014　100141A-100141A　2016年12月6日
出版者・発行元： SPIE
DOI： 10.1117/12.2243012 　

ISSN：0277-786X
Attosecond dynamical Franz-Keldysh effect in polycrystalline diamond 査読有り

M. Lucchini, S. A. Sato, A. Ludwig, J. Herrmann, M. Volkov, L. Kasmi, Y. Shinohara, K. Yabana, L. Gallmann, U. Keller

Science　353　(6302)　916-919　2016年8月26日
出版者・発行元： American Association for the Advancement of Science (AAAS)
DOI： 10.1126/science.aag1268 　

ISSN：0036-8075

eISSN：1095-9203

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Shining a fast light on diamonds Conceptually, the electronic structure of matter is a fixed scaffold of energy levels, which electrons climb with the help of light absorption. In reality, the light's electromagnetic field distorts the scaffold, a phenomenon that becomes increasingly evident with rising field intensity. Lucchini et al. studied a manifestation of this phenomenon, termed the dynamical Franz Keldysh effect, in diamond substrates exposed to sudden, moderately intense infrared fields. Using attosecond probe pulses and accompanying theoretical simulations, they resolved and accounted for the extremely rapid ensuing electron dynamics. Science , this issue p. 916
Attosecond nonlinear polarization and light–matter energy transfer in solids 査読有り

A. Sommer, E. M. Bothschafter, S. A. Sato, C. Jakubeit, T. Latka, O. Razskazovskaya, H. Fattahi, M. Jobst, W. Schweinberger, V. Shirvanyan, V. S. Yakovlev, R. Kienberger, K. Yabana, N. Karpowicz, M. Schultze, F. Krausz

Nature　534　(7605)　86-90　2016年5月23日
出版者・発行元： Springer Science and Business Media LLC
DOI： 10.1038/nature17650 　

ISSN：0028-0836

eISSN：1476-4687
Femtosecond time-resolved dynamical Franz-Keldysh effect 査読有り

T. Otobe, Y. Shinohara, S. A. Sato, K. Yabana

Physical Review B　93　(4)　2016年1月21日
出版者・発行元： American Physical Society (APS)
DOI： 10.1103/physrevb.93.045124 　

ISSN：2469-9950

eISSN：2469-9969
Controlling ultrafast currents by the nonlinear photogalvanic effect 査読有り

Georg Wachter, Shunsuke A Sato, Isabella Floss, Christoph Lemell, Xiao-Min Tong, Kazuhiro Yabana, Joachim Burgdörfer

New Journal of Physics　17　(12)　123026-123026　2015年12月21日
出版者・発行元： IOP Publishing
DOI： 10.1088/1367-2630/17/12/123026 　

eISSN：1367-2630
Protocol for observing molecular dipole excitations by attosecond self-streaking 査読有り

Georg Wachter, Stefan Nagele, Shunsuke A. Sato, Renate Pazourek, Michael Wais, Christoph Lemell, Xiao-Min Tong, Kazuhiro Yabana, Joachim Burgdörfer

Physical Review A　92　(6)　2015年12月18日
出版者・発行元： American Physical Society (APS)
DOI： 10.1103/physreva.92.061403 　

ISSN：1050-2947

eISSN：1094-1622
Nonlinear electronic excitations in crystalline solids using meta-generalized gradient approximation and hybrid functional in time-dependent density functional theory 査読有り

Shunsuke A. Sato, Yasutaka Taniguchi, Yasushi Shinohara, Kazuhiro Yabana

The Journal of Chemical Physics　143　(22)　2015年12月14日
出版者・発行元： AIP Publishing
DOI： 10.1063/1.4937379 　

ISSN：0021-9606

eISSN：1089-7690

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We develop methods to calculate electron dynamics in crystalline solids in real-time time-dependent density functional theory employing exchange-correlation potentials which reproduce band gap energies of dielectrics; a meta-generalized gradient approximation was proposed by Tran and Blaha [Phys. Rev. Lett. 102, 226401 (2009)] (TBm-BJ) and a hybrid functional was proposed by Heyd, Scuseria, and Ernzerhof [J. Chem. Phys. 118, 8207 (2003)] (HSE). In time evolution calculations employing the TB-mBJ potential, we have found it necessary to adopt the predictor-corrector step for a stable time evolution. We have developed a method to evaluate electronic excitation energy without referring to the energy functional which is unknown for the TB-mBJ potential. For the HSE functional, we have developed a method for the operation of the Fock-like term in Fourier space to facilitate efficient use of massive parallel computers equipped with graphic processing units. We compare electronic excitations in silicon and germanium induced by femtosecond laser pulses using the TB-mBJ, HSE, and a simple local density approximation (LDA). At low laser intensities, electronic excitations are found to be sensitive to the band gap energy: they are close to each other using TB-mBJ and HSE and are much smaller in LDA. At high laser intensities close to the damage threshold, electronic excitation energies do not differ much among the three cases.
Time-dependent density functional theory of high-intensity short-pulse laser irradiation on insulators 査読有り

S. A. Sato, K. Yabana, Y. Shinohara, T. Otobe, K.-M. Lee, G. F. Bertsch

Physical Review B　92　(20)　2015年11月12日
出版者・発行元： American Physical Society (APS)
DOI： 10.1103/physrevb.92.205413 　

ISSN：1098-0121

eISSN：1550-235X
Application of norm-conserving pseudopotentials to intense laser-matter interactions 査読有り

Xiao-Min Tong, Georg Wachter, Shunsuke A. Sato, Christoph Lemell, Kazuhiro Yabana, Joachim Burgdörfer

Physical Review A　92　(4)　2015年10月29日
出版者・発行元： American Physical Society (APS)
DOI： 10.1103/physreva.92.043422 　

ISSN：1050-2947

eISSN：1094-1622
Attosecond band-gap dynamics in silicon 査読有り

Martin Schultze, Krupa Ramasesha, C.D. Pemmaraju, S.A. Sato, D. Whitmore, A. Gandman, James S. Prell, L. J. Borja, D. Prendergast, K. Yabana, Daniel M. Neumark, Stephen R. Leone

Science　346　(6215)　1348-1352　2014年12月12日
出版者・発行元： American Association for the Advancement of Science (AAAS)
DOI： 10.1126/science.1260311 　

ISSN：0036-8075

eISSN：1095-9203

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Electron transfer from valence to conduction band states in semiconductors is the basis of modern electronics. Here, attosecond extreme ultraviolet (XUV) spectroscopy is used to resolve this process in silicon in real time. Electrons injected into the conduction band by few-cycle laser pulses alter the silicon XUV absorption spectrum in sharp steps synchronized with the laser electric field oscillations. The observed ~450-attosecond step rise time provides an upper limit for the carrier-induced band-gap reduction and the electron-electron scattering time in the conduction band. This electronic response is separated from the subsequent band-gap modifications due to lattice motion, which occurs on a time scale of 60 ± 10 femtoseconds, characteristic of the fastest optical phonon. Quantum dynamical simulations interpret the carrier injection step as light-field–induced electron tunneling.
Dielectric response of laser-excited silicon at finite electron temperature 査読有り

S. A. Sato, Y. Shinohara, T. Otobe, K. Yabana

Physical Review B　90　(17)　2014年11月11日
出版者・発行元： American Physical Society (APS)
DOI： 10.1103/physrevb.90.174303 　

ISSN：1098-0121

eISSN：1550-235X
Ab InitioSimulation of Electrical Currents Induced by Ultrafast Laser Excitation of Dielectric Materials 査読有り

Georg Wachter, Christoph Lemell, Joachim Burgdörfer, Shunsuke A. Sato, Xiao-Min Tong, Kazuhiro Yabana

Physical Review Letters　113　(8)　2014年8月18日
出版者・発行元： American Physical Society (APS)
DOI： 10.1103/physrevlett.113.087401 　

ISSN：0031-9007

eISSN：1079-7114
Efficient basis expansion for describing linear and nonlinear electron dynamics in crystalline solids 査読有り

Shunsuke A. Sato, Kazuhiro Yabana

Physical Review B　89　(22)　2014年6月30日
出版者・発行元： American Physical Society (APS)
DOI： 10.1103/physrevb.89.224305 　

ISSN：1098-0121

eISSN：1550-235X
Numerical pump-probe experiments of laser-excited silicon in nonequilibrium phase 査読有り

S. A. Sato, K. Yabana, Y. Shinohara, T. Otobe, G. F. Bertsch

Physical Review B　89　(6)　2014年2月10日
出版者・発行元： American Physical Society (APS)
DOI： 10.1103/physrevb.89.064304 　

ISSN：1098-0121

eISSN：1550-235X
First-principles simulation of the optical response of bulk and thin-film α-quartz irradiated with an ultrashort intense laser pulse 査読有り

Kyung-Min Lee, Chul Min Kim, Shunsuke A. Sato, Tomohito Otobe, Yasushi Shinohara, Kazuhiro Yabana, Tae Moon Jeong

Journal of Applied Physics　115　(5)　2014年2月7日
出版者・発行元： AIP Publishing
DOI： 10.1063/1.4864662 　

ISSN：0021-8979

eISSN：1089-7550

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A computational method based on a first-principles multiscale simulation has been used for calculating the optical response and the ablation threshold of an optical material irradiated with an ultrashort intense laser pulse. The method employs Maxwell's equations to describe laser pulse propagation and time-dependent density functional theory to describe the generation of conduction band electrons in an optical medium. Optical properties, such as reflectance and absorption, were investigated for laser intensities in the range 1010 W/cm2 to 2 × 1015 W/cm2 based on the theory of generation and spatial distribution of the conduction band electrons. The method was applied to investigate the changes in the optical reflectance of α-quartz bulk, half-wavelength thin-film, and quarter-wavelength thin-film and to estimate their ablation thresholds. Despite the adiabatic local density approximation used in calculating the exchange–correlation potential, the reflectance and the ablation threshold obtained from our method agree well with the previous theoretical and experimental results. The method can be applied to estimate the ablation thresholds for optical materials, in general. The ablation threshold data can be used to design ultra-broadband high-damage-threshold coating structures.
Maxwell + TDDFT multi-scale simulation for laser-matter interactions 査読有り

Shunsuke A. Sato, Kazuhiro Yabana

Journal of Advanced Simulation in Science and Engineering　1　(1)　98-110　2014年
出版者・発行元： Japan Society for Simulation Technology
DOI： 10.15748/jasse.1.98 　

eISSN：2188-5303
Nonadiabatic generation of coherent phonons 査読有り

Y. Shinohara, S. A. Sato, K. Yabana, J.-I. Iwata, T. Otobe, G. F. Bertsch

The Journal of Chemical Physics　137　(22)　2012年8月17日
出版者・発行元： AIP Publishing
DOI： 10.1063/1.4739844 　

ISSN：0021-9606

eISSN：1089-7690

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The time-dependent density functional theory (TDDFT) is the leading computationally feasible theory to treat excitations by strong electromagnetic fields. Here the theory is applied to coherent optical phonon generation produced by intense laser pulses. We examine the process in the crystalline semimetal antimony (Sb), where nonadiabatic coupling is very important. This material is of particular interest because it exhibits strong phonon coupling and optical phonons of different symmetries can be observed. The TDDFT is able to account for a number of qualitative features of the observed coherent phonons, despite its unsatisfactory performance on reproducing the observed dielectric functions of Sb. A simple dielectric model for nonadiabatic coherent phonon generation is also examined and compared with the TDDFT calculations.

︎全件表示 ︎最初の5件までを表示

MISC 1

高強度超短パルスレーザーと誘電体の相互作用を記述する第一原理計算

矢花一浩, 佐藤駿丞, 篠原康, 乙部智仁

固体物理 Vol.52 No.3　52　(3)　139-148　2017年3月
出版者・発行元：アグネ技術センター
ISSN： 0454-4544

講演・口頭発表等 5

First-Principles Electron Dynamics Simulations of Attosecond Phenomena in Solids 招待有り

Shunsuke A. Sato

Numerical Methods in Quantum Chemistry 2025
Quantum Electron Dynamics Simulation for Attosecond Phenomena 招待有り

Shunsuke A. Sato

Strong Matter-Field Interactions and Breakthrough Simulations of Future Semiconductor, UNIST, Ulsan, South Korea　2024年11月15日
Quantum Electron Dynamics Calculation for Attosecond Phenomena 招待有り

Shunsuke A. Sato

The 2nd International Conference on Nonequilibrium and Ultrafast Quantum States (NUQS-2024), Songshan Lake Materials Laboratory, Dongguan, China　2024年10月25日
First-principles electron dynamics calculations for light-induced ultrafast phenomena 招待有り

Shunsuke A. Sato

ALTA 2024　2024年5月2日
First-principles electron dynamics calculations for light-induced ultrafast phenomena 招待有り

Shunsuke A. Sato

ALTA 2024, Seogwipo KAL Hotel, Jeju, Korea　2024年5月3日

共同研究・競争的資金等の研究課題 8

アト秒光駆動電子物性の開拓

佐藤駿丞

提供機関：Japan Society for the Promotion of Science

制度名：Grants-in-Aid for Scientific Research

研究種目：Grant-in-Aid for Scientific Research (C)

研究機関：Tohoku University

2025年4月1日～ 2029年3月31日
THzメタマテリアル共振器によるフォノン強結合状態の実現と物性制御への応用

廣理英基, 佐藤駿丞

提供機関：Japan Society for the Promotion of Science

制度名：Grants-in-Aid for Scientific Research

研究種目：Grant-in-Aid for Scientific Research (B)

研究機関：Kyoto University

2021年4月1日～ 2025年3月31日

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テラヘルツ（THz）周波数帯の電磁場の量子揺らぎやレーザーから発生したテラヘルツ波を、新規な金属メタマテリアル共振器（キャビティ）を通して閉じ込め、物質中の素励起であるフォノン（格子振動）やマグノン（スピン集団運動）との強結合状態を実現することで物性の制御を目指している。昨年度の研究では、独自に開発した金属メタマテリアル構造を使用して、テラヘルツ周波数帯に磁気共鳴を持つ反強磁性体における非線形スピンダイナミクスを調べた。具体的には、ニオブ酸リチウム結晶を用いたパルス面傾斜法を使用して強力なテラヘルツパルスを生成する光学系を構築した。このテラヘルツパルスは最大でピーク電場振幅が1 MV/cmに達した。さらに、サンプル内部でさらに高い強度のテラヘルツ磁場パルスを発生させるために、新しい金属マイクロテラヘルツ共振器を考案した。この共振器が、1テスラ以上の強力なテラヘルツ磁場パルスをサンプル内部に発生させられることを確認した。この強力なテラヘルツ磁場パルスは、直径が約数マイクロメートルの空間領域に制限されているため、空間的に局所的なファラデー回転を測定する顕微鏡システムを構築した。この測定システムを使用して、反強磁性体において誘起された巨大な磁化変化を測定し、スピンの歳差運動の非線形振動を観測した。さらに、室温付近でスピン再配列相転移温度を示す反強磁性体に対して、超高速なスピンスイッチングを実現した。
THzメタマテリアル共振器によるフォノン強結合状態の実現と物性制御への応用

廣理英基, 佐藤駿丞

2021年4月1日～ 2025年3月31日

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「光による物性制御、及び新奇な物性の創発」は光物性物理分野の究極の目標の一つである。従来の高強度な光(レーザー)による物質駆動では、光から物質へのエネルギー移行に伴う熱の発生や破壊現象の誘発、あるいは散逸によるコヒーレンスの消失等の問題があり応用へ向けて解決すべき課題がある。本研究では、テラヘルツ（THz）周波数帯の「電磁場の量子揺らぎ」（ゼロ点振動場）を、金属メタマテリアル共振器（キャビティ）を通して閉じ込め、物質中のフォノン（格子振動）やマグノン（スピンの集団運動）との強結合状態を実現することで物性の制御を目指している。R３年度は、ハロゲン化ペロブスカイト半導体のCH3NH3PbI3の0.95THzのフォノン（Pb-I-Pb結合の振動）をナノ構造の分割リング共鳴器（SRR）で真空光子に結合し、最後にSRRのギャップを100nmに狭めていわゆる超強結合の実現を目指し、強いフォノン吸収（TOフォノン）をもつペロブスカイト半導体MAPbI3試料上にキャビティ強結合するリング型の金属メタマテリアル構造を試作した。結合強度を調べるために、ペロブスカイト膜でコーティングしたSRRの透過スペクトルを検出するTHz分光法の構築を行った。SRRの吸収ピークの周波数がフォノン周波数と等しいときにラビ分裂を観測した。
固体からの高次高調波発生の微視的機構に関する研究

2024年4月～ 2025年3月
光駆動非平衡定常状態を利用した物性制御理論の構築

2024年1月～ 2024年12月
光による電子構造制御の第一原理計算

佐藤駿丞

提供機関：Japan Society for the Promotion of Science

制度名：Grants-in-Aid for Scientific Research Grant-in-Aid for Early-Career Scientists

研究種目：Grant-in-Aid for Early-Career Scientists

研究機関：University of Tsukuba

2020年4月1日～ 2024年3月31日

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我々は、高強度な光によって駆動される物質中の電子ダイナミクスを微視的な理論計算により解析することで、光によって電子構造制御し物性を改変することを目指して研究を進めている。当該年度では、光励起された磁性体の電子構造の変化を調べるため、時間依存密度汎関数理論(TDDFT)に基づく第一原理計算により、レーザー励起された固体Co, Niの過渡的な光学応答を解析した。その結果、レーザーにより電子加熱により磁性が消失し、内殻電子の交換分裂が減少することによって内殻励起に対応する吸収端付近で光学応答変化が起こることが明らかとなった。この知見を応用し、光によって駆動された磁性体のスピンのダイナミクスを過渡的な光学測定によって調べる方法論を提案した。 <BR> さらに当該年度では、THz領域におけるグラフェンからの高次高調波発生を量子マスター方程式により解析した。従来の研究では、THz領域におけるグラフェンからの高次高調波発生は、熱力学的模型に基づく電子系の温度上昇に起因するものと理解されてきた。それに対し本研究では、THz光が駆動する電子系のダイナミクスを時間領域で数値シミュレーションすることにより、光が駆動する電子励起と固体内での電子緩和の競合によって生じる非平衡定常状態がTHz領域の高次高調波発生において重要な役割を果たすことが明らかとなった。 <BR> このような成果は、光によって物質の性質を超高速に制御するための技術の基盤となるものである。
First-principles investigation of the photovoltaic effect in ferroelectrics 競争的資金

提供機関：Alexander von Humboldt Foundation

制度名：Humboldt Research Fellowship for Postdoctoral Researchers

研究機関：Max Planck Institute for the Structure and Dynamics of Matter, Hamburg, Germany

2017年6月～ 2019年5月
アト秒電子ダイナミクスの第一原理計算

佐藤駿丞

提供機関：Japan Society for the Promotion of Science

制度名：Grants-in-Aid for Scientific Research Grant-in-Aid for JSPS Fellows

研究種目：Grant-in-Aid for JSPS Fellows

研究機関：University of Tsukuba

2014年4月25日～ 2017年3月31日

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平成28年度は、高強度・超短パルス光と物質の相互作用によっておこる極限的な非線形現象を微視的に理解するための理論的解析を行い、特に次の研究で成果があった。 (i)高強度フェムト秒レーザーが誘電体に誘起する超高速光学特性変化の第一原理計算この研究では、国外の実験グループとの共同研究により、高強度なフェムト秒パルスレーザーが引き起こす誘電体の超高速な光学特性の変化を調べた。特に、ダイアモンド薄膜に対する実験結果の理論解析においては、第一原理計算によって実験で観測される超高速光学特性変化を定量的によく再現することに成功した。さらに、ダイアモンドにおける超高速光学特性変化の微視的起源を明らかにするため、理論計により得られた情報をの詳細な解析を進めた。その結果、実験で観測された超高速な光学特性の変化は、高強度フェムト秒レーザーがダイアモンドの特定のバンド構造に引き起こすバンド内遷移(intra-band transition)に起因する動的Franz-Keldysh効果であることを明らかとなった。この成果は、論文"Attosecond dynamical Franz-Keldysh effect in polycrystalline diamond", Science 353, 916 (2016) としてScience誌から発表されている。また、さらにこの共同研究を発展させ、異なる物質・条件の下での超高速光学特性変化を実験と理論の両面から調べることにより、高強度超短パルスが引き起こすバンド内遷移、及びバンド間遷移(inter-band transition)からの異なる寄与の両方が超高速光学特性変化に対して重要な役割を果たすことが明らかとなってきた。

︎全件表示 ︎最初の5件までを表示