Updated on 2025/08/23

写真a

 
HANAI RYO
 
Organization
School of Science Associate Professor
Title
Associate Professor
External link

Degree

  • 博士（理学） ( 慶應義塾大学大学院 )

Research Interests

  • Active matter

  • Condensed matter physics

  • Open quantum systems

Research Areas

  • Natural Science / Semiconductors, optical properties of condensed matter and atomic physics

  • Natural Science / Magnetism, superconductivity and strongly correlated systems

  • Natural Science / Mathematical physics and fundamental theory of condensed matter physics

Research History

  • Institute of Science Tokyo   Department of Physics   Associate Professor

    2024.12

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    Country：Japan

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  • Kyoto University   Yukawa Institute for Theoretical Physics   Assistant Professor

    2022.10 - 2024.11

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    Country：Japan

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  • Asia Pacific Center for Theoretical Physics   Research Professor

    2022.10 - 2024.4

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    Country：Korea, Republic of

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  • Asia Pacific Center for Theoretical Physics   Junior Research Group Leader

    2022.3 - 2023.10

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  • Pohang University of Science and Technology   Department of Physics   Affiliate Faculty

    2022.3 - 2022.10

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    Country：Korea, Republic of

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  • University of Chicago   Pritzker School of Molecular Engineering   Postdoctoral Scholar

    2020.1 - 2021.4

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  • University of Chicago   James Franck Institute   Visiting Postdoctoral Scholar

    2017.11 - 2020.1

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  • Osaka University   JSPS’s Research Fellowship for Young Scientists (PD)

    2017.4 - 2020.1

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  • Keio University   Faculty of Science and Technology Department of Physics   JSPS’s Research Fellowship for Young Scientists (PD)

    2016.4 - 2017.3

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  • Keio University   Faculty of Science and Technology Department of Physics   JSPS’s Research Fellowship for Young Scientists (DC2)

    2015.4 - 2016.3

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Professional Memberships

Papers

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MISC

  • Universal scaling in one-dimensional non-reciprocal matter

    Shuoguang Liu, Ryo Hanai, Peter B. Littlewood

    2025.3

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  • Non-reciprocal interactions drive emergent chiral crystallites

    S. J. Kole, Xichen Chao, Abraham Mauleon-Amieva, Ryo Hanai, C. Patrick Royall, Tanniemola B. Liverpool

    2025.1

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    We study a new type of 2D active material that exhibits macroscopic phases
    with two emergent broken symmetries: self-propelled achiral particles that form
    dense hexatic clusters, which spontaneously rotate. We experimentally realise
    active colloids that self-organise into both polar and hexatic crystallites,
    exhibiting exotic emergent phenomena. This is accompanied by a field theory of
    coupled order parameters formulated on symmetry principles, including
    non-reciprocity, to capture the non-equilibrium dynamics. We find that the
    presence of two interacting broken symmetry fields leads to the emergence of
    novel chiral phases built from (2D) achiral active colloids (here Quincke
    rollers). These phases are characterised by the presence of both clockwise and
    counterclockwise rotating clusters. We thus show that spontaneous rotation can
    emerge in non-equilibrium systems, even when the building blocks are achiral,
    due to non-reciprocally coupled broken symmetries. This interplay leads to
    self-organized stirring through counter-rotating vortices in confined colloidal
    systems, with cluster size controlled by external electric fields.

    arXiv

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    Other Link： http://arxiv.org/pdf/2501.15996v1

  • Continuous time crystals as a PT symmetric state and the emergence of critical exceptional points

    Yuma Nakanishi, Ryo Hanai, Tomohiro Sasamoto

    2024.6

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    Continuous time-translation symmetry is often spontaneously broken in open
    quantum systems, and the condition for their emergence has been actively
    investigated. However, there are only a few cases in which its condition for
    appearance has been fully elucidated. In this Letter, we show that a
    Lindbladian parity-time ($\mathcal{PT}$) symmetry can generically produce
    persistent periodic oscillations in a wide class of systems. This includes
    one-collective spin models, which have been studied thoroughly in the context
    of dissipative continuous time crystals, and spatially extended bipartite
    bosonic systems with conserved particle number. Interestingly, the periodic
    orbits in the PT-symmetric phase are found to be center-type, implying an
    initial state dependence. These results are established by proving that the
    Lindbladian $\mathcal{PT}$ symmetry at the microscopic level implies a
    nonlinear PT symmetry, and by performing a linear stability analysis near the
    transition point. This research will further our understanding of novel
    non-equilibrium phases of matter and phase transitions with spontaneous
    anti-unitary symmetry breaking.

    arXiv

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    Other Link： http://arxiv.org/pdf/2406.09018v2

  • 非相反相転移の物理 Invited

    花井亮

    日本物理学誌   77 ( 10 )   666   2022.10

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    Authorship：Lead author   Language：Japanese   Publishing type：Article, review, commentary, editorial, etc. (scientific journal)  

    DOI： 10.11316/butsuri.77.10_666

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Presentations

  • Non-reciprocal frustration physics

    Ryo Hanai

    Long-term Workshop on Frontiers in Non-equilibrium Physics 2024  2024.7 

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    Event date： 2024.7

    Language：English   Presentation type：Oral presentation (general)  

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  • 非相反相互作用する開放量子スピン鎖に現れる普遍的性質

    Samuel Begg, 花井 亮

    日本物理学会年次大会  2023.9 

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    Event date： 2023.9

    Language：Japanese   Presentation type：Oral presentation (general)  

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  • Non-reciprocal frustration: time-crystalline order by disorder phenomena and glassy dynamics Invited

    Ryo Hanai

    Dynamical Days Asia Pacific 12 (DDAP12), PCS-IBS, Daejeon  2022.11 

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    Language：English   Presentation type：Oral presentation (invited, special)  

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  • Non-reciprocal frustrations: time-crystalline order by disorder phenomena and glassy dynamics Invited

    Ryo Hanai

    IBS-APCTP Conference on Advances in The Physics of Topological and Correlated Matter  2022.9 

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    Language：English   Presentation type：Oral presentation (invited, special)  

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  • Non-reciprocal frustration physics Invited

    Ryo Hanai

    Frontiers in nonequilibrium physics: active matter, topology and beyond  2023.7 

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    Language：English   Presentation type：Oral presentation (invited, special)  

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  • 非相反相転移とフラストレーション物理 Invited

    花井 亮

    統計物理学懇談会  2023.3 

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    Language：Japanese   Presentation type：Oral presentation (invited, special)  

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  • Dissipation engineering non-reciprocal spin-spin interactions via itinerant electrons

    Ryo Hanai, Rina Tazai, Daiki Ootsuki

    APS March Meeting 2024  2024.3 

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    Language：English   Presentation type：Oral presentation (general)  

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  • Non-reciprocal frustration physics Invited

    Ryo Hanai

    the programme at the Isaac Newton Institute for Mathematical Sciences in Cambridge, “New Statistical Physics of Living Matter: Non-equilibrium states under adaptive control”  2023.11 

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    Language：English   Presentation type：Oral presentation (invited, special)  

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  • Active quantum solids: photoinduced non-reciprocal magnetism Invited

    Ryo Hanai

    KITP Conference: The Many Faces of Active Mechanics  2024.10 

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    Language：English   Presentation type：Oral presentation (invited, special)  

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  • Photoinduced non-reciprocal phase transitions in strongly correlated materials

    Ryo Hanai

    APS March Meeting 2025  2025.3 

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  • 金属強磁性体における光誘起非相反相転移 Invited

    花井亮

    非平衡固体物理学の最前線, 京都  2024.11 

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    Language：Japanese   Presentation type：Oral presentation (invited, special)  

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Awards

  • 第17回（2023年）日本物理学会若手奨励賞

    2022.10   日本物理学会  

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Research Projects

  • 非平衡・非相反的アセンブリの物理則の基礎理論と解析技術の構築

    Grant number：25H01364  2025.4 - 2030.3

    日本学術振興会  科学研究費助成事業  学術変革領域研究(A)

    斉藤 稔

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    Grant amount：\212550000 （ Direct Cost: \163500000 、 Indirect Cost：\49050000 ）

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  • EPIC assembly: emergence of novel functional assembly by Evo-Physico Information Coupling

    Grant number：25A401  2025.4 - 2030.3

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research  Grant-in-Aid for Transformative Research Areas (A)

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  • EPIC Assembly: Emergence of novel functional assembly by Evo-Physico Information Coupling

    Grant number：25H01360  2025.4 - 2030.3

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research  Grant-in-Aid for Transformative Research Areas (A)

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    Grant amount：\209300000 （ Direct Cost: \161000000 、 Indirect Cost：\48300000 ）

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  • 固体電子系における光誘起非相反相互作用/相転移の物理

    Grant number：25K00935  2025.4 - 2028.3

    日本学術振興会  科学研究費助成事業  基盤研究(B)

    花井 亮

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    Grant amount：\18850000 （ Direct Cost: \14500000 、 Indirect Cost：\4350000 ）

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  • Non-reciprocal frustration physics

    Grant number：23K19034  2023.8 - 2025.3

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research  Grant-in-Aid for Research Activity Start-up

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    Grant amount：\2730000 （ Direct Cost: \2100000 、 Indirect Cost：\630000 ）

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  • Non-reciprocal many-body physics

    2023.6 - 2024.2

    National Research Foundation of Korea (NRF)  Individual Basic Research Projects (Leader, General Grant) 

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    Authorship：Principal investigator 

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  • Formation mechanism and dynamic critical phenomena of a non-equilibrium strongly correlated electron-hole condensate

    Grant number：17J01238  2017.4 - 2020.3

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research  Grant-in-Aid for JSPS Fellows

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    Grant amount：\4420000 （ Direct Cost: \3400000 、 Indirect Cost：\1020000 ）

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  • 励起子および励起子ポラリトン系における流入と流出のある凝縮体の非平衡強結合効果

    Grant number：15J02513  2015.4 - 2017.3

    日本学術振興会  科学研究費助成事業  特別研究員奨励費

    花井 亮

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    Grant amount：\2170000 （ Direct Cost: \1900000 、 Indirect Cost：\270000 ）

    励起子および励起子ポラリトン系は、電子・ホール等が強く相互作用すると同時に、対消滅や光子の共振器からの漏れによる粒子の流出が顕著であるため、非平衡性と強相関性が共存した系となっている。その結果、特に励起子ポラリトン系では、閉じた熱平衡系で実現するボース・アインシュタイン凝縮(BEC)から非平衡開放系の光学現象である半導体レーザー(LASER)へと移り変わる現象が観測されており、強相関凝縮系物理学とレーザー物理学をつなぐ架け橋となりうる系として注目を集めている。
    今年度は、Generalized random phase approximation(GRPA)をKeldysh形式に拡張することにより、非平衡定常状態にある励起子ポラリトン凝縮体の光学特性を解析することのできる枠組みを構築することに成功した。この枠組みを用いてphotoluminescenceを解析することで、ポンプ強度が上がるにつれ、励起子ポラリトン凝縮にブルーシフトが生じると同時に、拡散型ゴールドストーンモードのスペクトル強度が強くなっていくことを示した。これは実験結果を定性的に説明するものである。
    また、この系では長らく、（凝縮体のエネルギーを基準として）負のエネルギーを持つBogoliubov分散がphotoluminescenceに強く現れると予想されてきた。にもかかわらず、実際の実験ではこの「負の分散」が観測されないことが大きな謎とされていた。本研究の枠組みで解析した結果、「負の分散」のスペクトル強度は非平衡性により非常に弱くなることが分かり、外部からの連続的な粒子注入が「負の分散」の出現を大きく抑制することを明らかとした。
    本研究結果は、励起子ポラリトン系の多体効果を議論する際には非平衡性による分布の変化をきちんと考慮に入れる必要があることを示す結果として、重要であると考えている。

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