所属学科・専攻等 |
物理工学科 応用物理分野
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外部リンク |
論文
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Extraction of important degrees of freedom in quantum dynamics using singular value decomposition: Application to linear optical spectrum in two-dimensional Mott insulators 査読あり
Jun Tokimoto, Shu Ohmura, Akira Takahashi, Kaoru Iwano, and Hiroshi Okamoto
Physical Review B 109 ( 19 ) 195150-1 - 195150-14 2024年05月
記述言語:英語 掲載種別:研究論文(学術雑誌)
DOI: 10.1103/PhysRevB.109.195150
その他リンク: https://journals.aps.org/prb/abstract/10.1103/PhysRevB.109.195150
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Ultrafast polarization control in κ-(BEDT-TTF)2X 査読あり 国際誌
Shu Ohmura, Jun Tokimoto, Akira Takahashi
Physical Review B 104 ( 13 ) 134302 2021年10月
担当区分:筆頭著者 記述言語:英語 掲載種別:研究論文(学術雑誌) 出版者・発行元:American Physical Society
We present a theoretical investigation of the dynamics induced by higher-frequency off-resonant light pulse excitation in the metallic phase of κ−(BEDT−TTF)2X [where BEDT-TTF is bis(ethylenedithio)-tetrathiafulvalene and
X represents a counteranion] by solving the time-dependent Schrödinger equation numerically in the quarter-filled extended Hubbard model for the material. If the magnitude of the applied light pulse exceeds a critical value, the transition to the charge-ordered (CO) state is then induced by the light pulse excitation. In the CO state, one site forming a dimer becomes charge rich, the other site becomes charge poor, and the intradimer electric dipole moments are aligned in a particular direction. The transition is driven by photoinduced reduction of the effective transfer integrals and can therefore be regarded as a dynamical localization-related phenomenon. There are two degenerate A phase and B phase CO states that have opposite polarization directions. The photogenerated CO state is given by the superposition of the A phase and B phase CO states with equal weights, and the polarization of the photogenerated CO state is effectively zero. Transitions to either of the two polarized CO states can be induced selectively, and the polarization can be generated by excitation using light and terahertz pulses. Furthermore, the polarization can be reversed on a timescale of several tens of femtoseconds by excitation using double light and terahertz pulses, which induce the following phase transitions: metal → polarized CO state of the A (B) phase → metal → polarized CO state of the B (A) phase
→ metal.DOI: 10.1103/PhysRevB.104.134302
その他リンク: https://journals.aps.org/prb/abstract/10.1103/PhysRevB.104.134302
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Analysis of the multielectron dynamics in intense laser-induced ionization of CO by the time-dependent effective potentials for natural orbitals 査読あり
Shu Ohmura, Tsuyoshi Kato, Hideki Ohmura, Shiro Koski, Hirohiko Kono
Journal of Physics B: Atomic, Molecular and Optical Physics 53 ( 18 ) 184001 2020年07月
担当区分:筆頭著者 記述言語:英語 掲載種別:研究論文(学術雑誌) 出版者・発行元:IOPscience
We simulated the multielectron dynamics of a CO molecule irradiated by near-IR λ = 760 nm
two-cycle pulses with different carrier envelope phases by using the multiconfiguration
time-dependent (TD) Hartree–Fock (MCTDHF) method. The ionization rate estimated from
the simulations is higher when the laser electric field ε(t) points from C to O than in the
opposite case, in agreement with the results of two-color experiments. The mechanism of the
directional anisotropy in tunnel ionization of CO was examined by converting the obtained
multielectron dynamics to the representation in terms of TD natural orbitals {φj(t)}. Within
the framework of MCTDHF, we derived the equations of motion for {φj(t)}. From the derived
equations, we defined the TD effective potentials veffj(t) that govern the dynamics of φj(t).
veffj(t) consists of the one-body part v1(t) including the interaction with ε(t) and the two-body
part v2,j(t) originating from electron–electron interaction. In veff5σ(t) for the 5σ HOMO, a
narrow hump associated with the increase in v2,5σ(t) is surmounted on the field-distorted
barrier of v1(t) + v2,5σ(0) near the nucleus C when ε(t) points from C to O, which results in
the anisotropic ionization of CO. For 4σ, a high barrier that suppresses ionization is formed in
veff4σ(t) when ε(t) points from C to O, which suggests that dynamical correlation exists between
4σ and 5σ electrons on route to ionization. For the opposite phase, veff4σ(t) becomes barrierless,
enhancing high-harmonic generation through 4σ. We also simulated the dynamics for a
λ = 380 nm pulse to investigate how veff5σ(t) reflects the nonadiabatic electronic response
to the pulse. We found that the height of the hump in v1(0) + v2,5σ(t) is nearly proportional
to the induced dipole moment of φ5σ(t), irrespective of whether the response is adiabatic
or not. The veffHOMO(t) for LiH is also presented to demonstrate the ubiquity of hump structures.その他リンク: https://iopscience.iop.org/article/10.1088/1361-6455/ab9f0e
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Time-dependent effective potential for the ultrafast correlated electron dynamics of molecules in intense laser fields: Application to anisotropic ionization of CO 査読あり 国際誌
Hirohiko Kono, Shu Ohmura, Tsuyoshi Kato, Hideki Ohmura, Shiro Koseki
Journal of Physics: Conference Series 1412 ( 4 ) 042004 2020年06月
記述言語:英語 掲載種別:研究論文(国際会議プロシーディングス) 出版者・発行元:IOPscience
By using the multiconfiguration time-dependent (TD) Hartree-Fock (MCTDHF) method, we simulated the multielectron dynamics of a CO molecule irradiated by near-IR two-cycle pulses with different carrier envelope phases. The ionization rate calculated is higher when the laser electric field ε(t) points from the nucleus C to O than the opposite case, in agreement
with the results of two-color ionization experiments. The mechanism of anisotropic tunnel ionization in CO was examined by converting the obtained multielectron dynamics to the representation in terms of TD natural orbitals {φ#DjR(t)}. Within the framework of MCTDHF, we derived the unitary equations of motion for {φj(t)}. From the derived equations, we defined the TD effective potentials {veffj(t)} that govern the dynamics of {φ#Dj(t)}. In veff5σ(t) for the 5σ HOMO, a narrow hump that originates from two-body electron-electron repulsion is formed on the top of the field-induced distorted barrier near the nucleus C when ε(t) points from C to O, which is responsible for the directional anisotropy of tunnel ionization. For 4σ HOMO-2, a high
barrier to suppress ionization is formed in veff4σ(t) when ε(t) points from C to O, in correlation with the electron-electron interaction with a 5σ electron on route to ionization. For the opposite
phase, veff4σ(t) becomes barrierless, which enhances high-harmonic generation through φ4σ(t).DOI: 10.1088/1742-6596/1412/4/042004
その他リンク: https://iopscience.iop.org/article/10.1088/1742-6596/1412/4/042004
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A charge model as an effective model of one-dimensional Hubbard and extended Hubbard systems: its application to linear optical spectrum calculations in large systems based upon many-body Wannier functions 査読あり 国際誌
Shu Ohmura, Akira Takahashi, Kaoru Iwano, Tokitake Yamaguchi, Kazuya Shinjo, Takami Tohyama, Shigetoshi Sota, Hiroshi Okamoto
Physical Review B 2019年12月
担当区分:筆頭著者 記述言語:英語 掲載種別:研究論文(学術雑誌)
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Terahertz pulse induced transitions between ionic and neutral phases and electronic polarization reversal in TTF-CA 査読あり 国際誌
Shu Ohmura, Tomohito Mase, Akira Takahashi
Physical Review B 2019年07月
担当区分:筆頭著者 記述言語:英語 掲載種別:研究論文(学術雑誌)
MISC
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An Effective Model for the One-Dimensional Extended Hubbard Model Applicable to Linear Optical Spectrum Calculations in Large Systems: A New Approach Based on Many-Body Wannier Functions
Shu Ohmura, Akira Takahashi, Kaoru Iwano, Tokitake Yamaguchi, Kazuya Shinjo, Takami Tohyama, Shigetoshi Sota, Hiroshi Okamoto
Photon Factory Highlights 2019 2020年11月
担当区分:筆頭著者 記述言語:英語 掲載種別:記事・総説・解説・論説等(大学・研究所紀要) 出版者・発行元:KEK 高エネルギー加速器研究機構
We have developed a charge model as an effective model of the one-dimensional extended Hubbard model based on
the spin-charge separation. The charge model includes the effect of charge fluctuations and is applicable to the photoexcitation of one-dimensional Mott insulators. It is numerically shown that the charge model reproduces the optical conductivity spectra calculated by the original model quantitatively. In order to calculate a larger system to compare with experimental results, we also developed a method of many-body Wannier functions (MBWFs). We succeeded in obtaining the optical conductivity spectrum for a large enough system by using the MBWFs constructed from the photoexcited states of the charge model.
講演・口頭発表等
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電荷移動型金属有機構造体(NPr4)2[Fe2(Cl2An)3]における光励起状態
加藤誉久、大村周、高橋聡
日本物理学会第79回年次大会 2024年09月 日本物理学会
開催年月日: 2024年09月
記述言語:日本語 会議種別:ポスター発表
開催地:北海道大学(札幌キャンパス) 国名:日本国
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TTF-CAのイオン性相および中性相における光励起によるドメイン生成
大村周、高橋聡
日本物理学会第79回年次大会 2024年09月 日本物理学会
開催年月日: 2024年09月
記述言語:日本語 会議種別:口頭発表(一般)
開催地:北海道大学(札幌キャンパス) 国名:日本国
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Analysis of Strong Photoexcitations in Two-Dimensional Mott Insulators Using Singular Value Decomposition 国際会議
Shu Ohmura, Yusuke Umemura, and Akira Takahashi
PIPT8 2024年06月 Marilou de Wit
開催年月日: 2024年06月
記述言語:英語 会議種別:ポスター発表
開催地:Concertgebouw De Vereeniging (Nijmegen) 国名:オランダ王国
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TTF-CAの光吸収スペクトルにおけるギャップ内電子励起状態の解析
小野佑介、大村周、高橋聡
日本物理学会2024年春季大会 2024年03月 日本物理学会
開催年月日: 2024年03月
記述言語:日本語 会議種別:ポスター発表
開催地:オンライン 国名:日本国
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特異値分解を用いたα-(BEDT-TTF)2I3の光励起状態の解析
中西航、大村周、高橋聡
日本物理学会2024年春季大会 2024年03月 日本物理学会
開催年月日: 2024年03月
記述言語:日本語 会議種別:ポスター発表
開催地:オンライン 国名:日本国
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1次元モット絶縁体の光誘起金属転移における電荷揺らぎの効果II
大村周、久嶋一毅、月元奎輔、高橋聡
日本物理学会2024年春季大会 2024年03月 日本物理学会
開催年月日: 2024年03月
会議種別:口頭発表(一般)
開催地:オンライン 国名:日本国
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2次元モット絶縁体の光強励起時に現れるギャップ内状態
大村周、梅村優佑、時本純、高橋聡
日本物理学会2022年秋季大会 2022年09月 日本物理学会
開催年月日: 2022年09月
記述言語:日本語 会議種別:口頭発表(一般)
開催地:東京工業大学
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光強励起された1次元モット絶縁体における光の衣をまとった状態の時間分解特異値分解による解析
久嶋一毅, 大村周, 時本純, 高橋聡
日本物理学会2022年秋季大会 2022年09月 日本物理学会
開催年月日: 2022年09月
記述言語:日本語 会議種別:ポスター発表
開催地:東京工業大学
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Analysis of Photo-Excited States of the 2D Mott Insulator Using Randomized Singular Value Decomposition 国際会議
Jun Tokimoto, Shu Ohmura, Akira Takahashi, Takami Tohyama
29th International Conference on Low Temperature Physics 2022年08月
開催年月日: 2022年08月
記述言語:英語 会議種別:ポスター発表
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時間分解特異値分解による1次元モット絶縁体における光誘起金属転移初期過程の解析
大村 周、時本 純、高橋 聡
第77回年次大会(2022年) 2022年03月 日本物理学会
開催年月日: 2022年03月
記述言語:日本語 会議種別:口頭発表(一般)
開催地:オンライン開催