写真a

TAKAYOSHI Shintaro

Position

Associate Professor

Homepage URL

https://sites.google.com/site/shintarotakayoshi/english_top

External Link

Graduating School 【 display / non-display

  • The University of Tokyo   Faculty of Science   Graduated

    2003.4 - 2007.3

Graduate School 【 display / non-display

  • The University of Tokyo   Graduate School, Division of Science   Doctor's Course   Completed

    2009.4 - 2012.3

  • The University of Tokyo   Graduate School, Division of Science   Master's Course   Completed

    2007.4 - 2009.3

Studying abroad experiences 【 display / non-display

  • 2018.9
    -
    2020.3

    Max Planck Institute for the Physics of Complex Systems  

  • 2015.9
    -
    2018.9

    University of Geneva  

Campus Career 【 display / non-display

  • KONAN UNIVERSITY   Faculty of Science and Engineering   Faculty of Science and Engineering Department of Physics   Associate Professor

    2020.4

External Career 【 display / non-display

  • Max Planck Institute for the Physics of Complex Systems

    2018.9 - 2020.3

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    Country:Germany

  • University of Geneva   Department of Quantum Matter Physics

    2015.9 - 2018.9

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    Country:Switzerland

  • The University of Tokyo   School of Science, Department of Physics

    2015.5 - 2015.8

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    Country:Japan

  • National Institute for Materials Science

    2013.4 - 2015.4

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    Country:Japan

  • The University of Tokyo   School of Engineering, Department of Applied Physics

    2012.8 - 2013.3

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    Country:Japan

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Papers 【 display / non-display

  • Scanning Tunneling Microscopy as a Single Majorana Detector of Kitaev's Chiral Spin Liquid Reviewed

    Masafumi Udagawa, Shintaro Takayoshi, Takashi Oka

    PHYSICAL REVIEW LETTERS   126 ( 12 )   127201   2021.3

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    Joint Work

    Publisher:AMER PHYSICAL SOC  

    We propose a local detection scheme for the Majorana zero mode (MZM) carried by a vison in Kitaev's chiral spin liquid (CSL) using scanning tunneling microscopy (STM). The STM introduces a single Majorana into the system through hole-charge injection and the Majorana interacts with the MZM to form a stable composite object. We derive the exact analytical expression of single-hole Green's function in the Mott insulating limit of Kitaev's model, and show that the differential conductance has split peaks, as a consequence of resonant tunneling through the vison-hole composite. The peak splitting turns out comparable to the Majorana gap in CSL, well within the reach of experimental observation.

    DOI: 10.1103/PhysRevLett.126.127201

  • Diagrammatic study of optical excitations in correlated systems Reviewed

    Olivier Simard, Shintaro Takayoshi, Philipp Werner

    PHYSICAL REVIEW B   103 ( 10 )   104415   2021.3

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    Publisher:AMER PHYSICAL SOC  

    The optical conductivity contains relevant information on the properties of correlated electron systems. In infinite dimensions, where dynamical mean field theory becomes exact, vertex corrections can be neglected and the conductivity computed from particle-hole bubbles. An interesting question concerns the nature and effect of the most relevant vertex corrections in finite-dimensional systems. A recent numerical study showed that the dominant vertex correction near an ordering instability with wave vector pi comes from a vertical ladder, analogous to the Maki-Thompson diagram. Since the random phase approximation version of this ladder diagram, dubbed pi-ton, can be easily evaluated, this suggests a simple procedure for incorporating antiferro-magnetic or charge density wave fluctuations into dynamical mean field estimates of the optical conductivity and related susceptibilities. We implement this procedure for the half-filled Hubbard model, considering the pi-ton, a double-ladder extension of the pi-ton and Aslamazov-Larkin-type diagrams, and reveal the spectral signatures of these vertex corrections.

    DOI: 10.1103/PhysRevB.103.104415

  • High-harmonic generation in one-dimensional Mott insulators Reviewed

    Yuta Murakami, Shintaro Takayoshi, Akihisa Koga, Philipp Werner

    PHYSICAL REVIEW B   103 ( 3 )   035110   2021.1

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    Publisher:AMER PHYSICAL SOC  

    We study high-harmonic generation (HHG) in the one-dimensional Hubbard model in order to understand its relation to elementary excitations as well as the similarities and differences to semiconductors. The simulations are based on the infinite time-evolving block decimation (iTEBD) method and exact diagonalization. We clarify that the HHG originates from the doublon-holon recombination, and the scaling of the cutoff frequency is consistent with a linear dependence on the external field. We demonstrate that the subcycle features of the HHG can be reasonably described by a phenomenological three step model for a doublon-holon pair. We argue that the HHG in the one-dimensional Mott insulator is closely related to the dispersion of the doublon-holon pair with respect to its relative momentum, which is not necessarily captured by the single-particle spectrum due to the many-body nature of the elementary excitations. For the comparison to semiconductors, we introduce effective models obtained from the Schrieffer-Wolff transformation, i.e., a strong-coupling expansion, which allows us to disentangle the different processes involved in the Hubbard model: intraband dynamics of doublons and holons, interband dipole excitations, and spin exchanges. These demonstrate the formal similarity of the Mott system to the semiconductor models in the dipole gauge, and reveal that the spin dynamics, which does not directly affect the charge dynamics, can reduce the HHG intensity. We also show that the long-range component of the intraband dipole moment has a substantial effect on the HHG intensity, while the correlated hopping terms for the doublons and holons essentially determine the shape of the HHG spectrum. A new numerical method to evaluate single-particle spectra within the iTEBD method is also introduced.

    DOI: 10.1103/PhysRevB.103.035110

  • Optomagnonic Barnett effect Reviewed

    Kouki Nakata, Shintaro Takayoshi

    PHYSICAL REVIEW B   102 ( 9 )   094417   2020.9

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    Publisher:AMER PHYSICAL SOC  

    Combining the technologies of quantum optics and magnonics, we find that the circularly polarized laser can dynamically realize the quasiequilibrium magnon Bose-Einstein condensates (BEC). The Zeeman coupling between the laser and spins generates the optical Barnett field, and its direction is controllable by switching the laser chirality. We show that the optical Barnett field develops the total magnetization in insulating ferrimagnets with reversing the local magnetization, which leads to the quasiequilibrium magnon BEC. This laser-induced magnon BEC transition through optical Barnett effect, dubbed the optomagnonic Barnett effect, provides an access to coherent magnons in the high-frequency regime of the order of terahertz. We also propose a realistic experimental setup to observe the optomagnonic Barnett effect using current device and measurement technologies as well as the laser chirping. The optomagnonic Barnett effect is a key ingredient for the application to ultrafast spin transport.

    DOI: 10.1103/PhysRevB.102.094417

  • Ultrafast nonequilibrium evolution of excitonic modes in semiconductors Reviewed

    Yuta Murakami, Michael Schueler, Shintaro Takayoshi, Philipp Werner

    PHYSICAL REVIEW B   101 ( 3 )   035203   2020.1

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    Publisher:AMER PHYSICAL SOC  

    We study the time evolution of excitonic states after photoexcitation in the one-dimensional spinless extended Falicov-Kimball model. Several numerical methods are employed and benchmarked against each other: time-dependent mean-field simulations, the second-Born approximation (2BA) within the Kadanoff-Baym formalism, the generalized Kadanoff-Baym ansatz (GKBA) implemented with the 2BA, and the infinite time-evolving block decimation (iTEBD) method. It is found that the GKBA gives the best agreement with iTEBD and captures the relevant physics. Excitations to the particle-hole continuum and resonant excitations of the equilibrium exciton result in a qualitatively different dynamics. In the former case, the exciton binding energy remains positive and the frequency of the corresponding coherent oscillations is smaller than the band gap. On the other hand, resonant excitations trigger a collective mode whose frequency is larger than the band gap. We discuss the origin of these different behaviors by evaluating the nonequilibrium susceptibility using the nonthermal distribution and a random phase approximation. The peculiar mode with frequency larger than the band gap is associated with a partial population inversion with a sharp energy cutoff. We also discuss the effects of the cooling by a phonon bath. We demonstrate the real-time development of coherence in the polarization, which indicates excitonic condensation out of equilibrium.

    DOI: 10.1103/PhysRevB.101.035203

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Review Papers (Misc) 【 display / non-display

  • Field theoretical approach to the entanglement spectrum of AKLT states

    Tanaka Akihiro, Takayoshi Shintaro

    Meeting Abstracts of the Physical Society of Japan   72 ( 0 )   2419 - 2419   2017

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    Publisher:The Physical Society of Japan  

    DOI: 10.11316/jpsgaiyo.72.2.0_2419

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  • Theoretical Study towards Ultrafast Spintronics

    Sato Masahiro, Takayoshi Shintaro, Oka Takashi

    Butsuri   72 ( 11 )   783 - 792   2017

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    Publisher:The Physical Society of Japan  

    <p>In this article, we explain our theoretical proposals, ultrafast ways of controlling magnetic properties of solid (magnetization, spin chirality, spin currents, etc.) by laser. We first review the Floquet theorem, which is useful for the prediction of novel laser-induced phenomena, then we turn to our recent results. We cover the following topics: laser-induced magnetization growing process, laser-driven spin chirality and spin current in multiferroics, and topological spin liquid state realized by laser in the honeycomb Kitaev model.</p>

    DOI: 10.11316/butsuri.72.11_783

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  • 3d AKLT like SPT states in terms as a dual to the O(6) nonlinear sigma model

    Tanaka Akihiro, Takayoshi Shintaro

    Meeting Abstracts of the Physical Society of Japan   71 ( 0 )   2755 - 2755   2016

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    Publisher:The Physical Society of Japan  

    DOI: 10.11316/jpsgaiyo.71.2.0_2755

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  • Strange correlator in symmetry protected topological phases of quantum spin systems

    Takayoshi Shintaro, Tanaka Akihiro

    Meeting Abstracts of the Physical Society of Japan   71 ( 0 )   2756 - 2756   2016

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    Publisher:The Physical Society of Japan  

    DOI: 10.11316/jpsgaiyo.71.2.0_2756

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  • 16aCQ-12 Pair Tomonaga-Luttinger liquid phase in a Bose-Hubbard model with flat bands

    Katsura Hosho, Takayoshi Shintaro, Watanabe Noriaki, Aoki Hideo

    Meeting Abstracts of the Physical Society of Japan   70 ( 0 )   2536 - 2536   2015

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    Publisher:The Physical Society of Japan  

    DOI: 10.11316/jpsgaiyo.70.2.0_2536

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