Nago, Yusuke

写真a

Affiliation

Faculty of Science and Technology, Department of Physics ( Yagami )

Position

Research Associate/Assistant Professor/Instructor
Scopus Paper Info  
Paper Count: 32 Citation Count: 269 h-index: 9

Click to view the Scopus page. The data was downloaded from Scopus API in September 06, 2026, via http://api.elsevier.com and http://www.scopus.com .

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Other Affiliation 【 Display / hide 】

  • japan women's university, 非常勤講師

  • 東京大学 低温科学研究センター, 村川研究室, 客員共同研究員

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Career 【 Display / hide 】

  • 2011.10
    -
    2012.03

    大阪市立大学, 理学研究科, 特任助教

  • 2013.04
    -
    2016.03

    東京理科大学, 理学部応用物理学科, 嘱託助教

  • 2014.06
    -
    2018.03

    理化学研究所, 創発物性科学研究センター 量子情報エレクトロニクス部門　量子凝縮相研究チーム, 客員研究員

  • 2019.04
    -
    Present

    東京大学, 低温科学研究センター, 客員共同研究員

  • 2025.04
    -
    Present

    日本女子大学, 理学部　数物情報科学科

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Academic Background 【 Display / hide 】

  • 2001.04
    -
    2005.03

    Osaka City University, 理学部, 物理学科

    University, Graduated, Other

  • 2005.04
    -
    2007.03

    Osaka City University, 理学研究科, 数物専攻

    Graduate School, Completed, Master's course

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Academic Degrees 【 Display / hide 】

  • Doctor of Science, Osaka City University, Coursework, 2011.09

    Vortex Generation Induced by an Object Oscillating in Superfluid 3He-B

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Research Areas 【 Display / hide 】

  • Natural Science / Magnetism, superconductivity and strongly correlated systems (量子流体固体、超流動、量子渦量子乱流、NEMS/MEMS、ジョセフソン接合、SQUID)

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Research Keywords 【 Display / hide 】

  • Superfluidity、Superconductivity

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Papers 【 Display / hide 】

  • 4D-XY Superfluid Transition and Dissipation in 4He Confined in Nanoporous Media

    Tani T., Nago Y., Murakawa S., Shirahama K.

    Journal of the Physical Society of Japan (The Physical Society of Japan)  91   014603-1 - 014603-20 2022.01

    Research paper (scientific journal), Joint Work, Accepted,  ISSN  00319015

    　View Summary

    4He confined in nanoporous Gelsil glass is a unique, strongly correlated Bose system exhibiting quantum phase transition (QPT) by controlling pressure. Previous studies revealed that the QPT occurs with four-dimensional (4D) XY criticality, which appears in the zero-temperature limit of the superfluid density. However, the P-T phase diagram also suggested that the 4D XY nature appears at finite temperatures. Here, we have determined the critical exponent of the superfluid density ρsof 4He in two Gelsil samples that have pore diameter to be about 3 nm, using a newly developed mechanical resonator technique. The critical exponent ζ in the powerlaw fitting ρsα |1 - T=Tc|ζ, where Tcis the superfluid transition temperature, was found to be 1.0 ± 0.1 for all pressures realized in this experiment, 0.1 > P > 2.4 MPa. This value of ζ gives decisive evidence that the finite-temperature superfluid transition belongs to the 4D XY universality class. The emergence of the 4D XY criticality is explained by the existence of many nanoscale superfluid droplets, the so-called localized Bose-Einstein condensates (LBECs), above Tc. Due to the large energy cost for 4He atoms to move between the LBECs, the phase of the LBEC order parameters fluctuates not only in spatial (3D) but imaginary time (+1D) dimensions, resulting in the 4D XY criticality by a temperature near Tc. Since the finite size of the system in the imaginary time dimension Ltis larger than the pore size, the 4D XY critical phenomenon is observed. In the very vicinity of Tcat which the correlation length exceeds Lt, there may be a crossover from 4D to 3D XY criticality. Below Tc, macroscopic superfluidity grows in the nanopores of Gelsil by the alignment of the phases of the LBEC order parameters. An excess dissipation peak observed below Tc is well explained by this phase-matching process.

  • Evidence for 4D XY Quantum Criticality in 4He Confined in Nanoporous Media at Finite Temperatures

    Tomoyuki Tani, Yusuke Nago, Satoshi Murakawa, and Keiya Shirahama

    Journal of the Physical Society of Japan (Physical Society of Japan)  90 ( 3 ) 033601-1 - 033601-5 2021.02

    Research paper (scientific journal), Joint Work, Accepted,  ISSN  00319015

    　View Summary

    4He confined in nanoporous media is a model Bose system that exhibits quantum phase transition (QPT) by varying pressure. We have precisely determined the critical exponent of the superfluid density of liquid 4He in porous Gelsil glasses with pore size of 3.0 nm using the Helmholtz resonator technique. The critical exponent ζ of the superfluid density was found to be 1.0 ± 0.1 for the pressure range 0.1 < P < 2.4 MPa. This value provides decisive evidence that the finite-temperature superfluid transition belongs to the four-dimensional (4D) XY universality class, in contrast to the classical 3D XY one in bulk liquid 4He, in which ζ = 0.67. The quantum critical behavior at a finite temperature is understood by strong phase fluctuations in local Bose-Einstein condensates above the superfluid transition temperature. 4He in nanoporous media is a unique example in which quantum criticality emerges not only at 0K but at finite temperatures.

  • Multiple Diffusion-Freezing Mechanisms in Molecular-Hydrogen Films

    T. Makiuchi, K. Yamashita, M. Tagai, Y. Nago, and K. Shirahama

    Physical Review Letters 123   245301-1 - 245301-5 2019.12

    Research paper (scientific journal), Joint Work, Accepted

    　View Summary

    Molecular hydrogen is a fascinating candidate for novel bosonic and fermionic superfluids. We have
    studied diffusion dynamics of thin films of H2, HD, and D2 adsorbed on a glass substrate by measurements
    of elasticity. The elasticity shows multiple anomalies well below the bulk triple point temperature. They are
    attributed to three different diffusion mechanisms of admolecules and their “freezing” into a localized state:
    classical thermal diffusion of vacancies, quantum tunneling of vacancies, and diffusion of molecules in
    the uppermost surface. The surface diffusion is active down to 1 K, below which the molecules become
    localized. This suggests that the surface layer of hydrogen films is on the verge of quantum phase transition
    to a superfluid state.

  • Elastic Anomaly of Thin Neon Film

    Makiuchi Takahiko, Yamashita Katsuyuki, Tagai Michihiro, Nago Yusuke, Shirahama Keiya

    Journal of the Physical Society of Japan (Physical Society of Japan)  88 ( 3 ) 34601-1 - 34601-6 2019.02

    Research paper (scientific journal), Joint Work, Accepted,  ISSN  00319015

    　View Summary

    © 2019 The Physical Society of Japan. Adsorbed molecular films provide two-dimensional systems that show various emergent phenomena that are not observed in bulk counterparts. We have measured the elasticity of thin neon films adsorbed on porous glass down to 1 K by the torsional oscillator technique. The shear modulus of a neon film anomalously increases at low temperatures with excess dissipation. This behavior indicates a crossover from a soft (fluidlike) state at high temperatures to a stiff (solidlike) state at low temperatures. The temperature dependence of the anomaly is qualitatively similar to that of the elastic anomaly of helium films found in our recent study. The dissipation peak temperature, however, becomes constant at about 5 K, contrary to the case of helium, in which it decreases to 0 K at a critical coverage of a quantum phase transition between a gapped localized phase and a mobile (superfluid) phase. It is concluded that neon films behave as a classical system that does not show a quantum phase transition or superfluidity, although the films may be strongly supercooled to temperatures much lower than the bulk triple point, 24.6 K. Our results suggest that the elastic anomaly is a universal phenomenon of atomic or molecular films adsorbed on disordered substrates.

  • Elastic anomaly of helium films at a quantum phase transition

    Makiuchi T, Tagai M, Nago Y, Takahashi D, Shirahama K

    Physical Review B (Physical Review B)  98 ( 23 ) 235104-1 - 235104-10 2018.12

    Research paper (scientific journal), Joint Work, Accepted,  ISSN  24699950

    　View Summary

    © 2018 American Physical Society. Helium films show various quantum phases that undergo quantum phase transitions by changing coverage n. We found anomalous elastic phenomena in bosonic He4 and fermionic He3 films adsorbed on a glass substrate. The films stiffen under ac strain at low temperature with an excess dissipation. The onset temperature of the stiffening decreases to 0 K as n approaches a critical coverage nc. The elastic anomaly is explained by thermal activation of helium atoms from the localized to extended states with a distributed energy gap. We determine the energy band structure of helium films from elasticity. The ground states of He4 and He3 at n<nc, which are possibly a sort of Mott insulator or Mott glass, are identically gapped and compressible.

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Papers, etc., Registered in KOARA 【 Display / hide 】

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Reviews, Commentaries, etc. 【 Display / hide 】

  • 信貴賞受賞者からのメッセージ 「信貴賞受賞から現在の低温物性研究に至るまで」

    永合祐輔

    「低温工学・超電導の未来に向けて」関西支部発足50周年記念特集 (公益社団法人 低温工学・超電導学会関西支部)   2023.12

    Other, Single Work, Lead author

  • 4次元相転移は実在する– ナノ多孔体中ヘリウムの有限温度量子臨界現象

    白濱圭也、谷智行、永合祐輔

    固体物理 (アグネ技術センター)  57 ( 6 ) 33 - 43 2022.06

    Article, review, commentary, editorial, etc. (scientific journal), Joint Work

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Presentations 【 Display / hide 】

  • Dielectric anomaly of 4He films adsorbed on alumina nanopowder

    S. Nakajima, Y. Nago and K. Shirahama

    [International presentation]  International Symposium on Quantum Fluids and Solids(QFS2026) (University of Notre Dame) , 

    2026.08
    , 

    Poster presentation

  • Effect of helium adsorption on the dielectric properties of LiNbO3

    So Hirao, Hiroki Tsuchiya, Yusuke Nago, Keiya Shirahama

    [International presentation]  International Symposium on Quantum Fluids and Solids(QFS2026), 

    2026.08
    , 

    Poster presentation

  • Heat-capacity measurement of 4He films adsorbed on hexagonal boron nitride

    Jean-Paul van Woensel, Yusuke Nago and Keiya Shirahama

    [International presentation]  International Symposium on Quantum Fluids and Solids(QFS2026), 

    2026.08
    , 

    Poster presentation

  • Multiple Phase Slip Phenomenon in 4He Superflow through a Newly Developed Microslit Structure

    Tomoyuki Tani, Ryoma Wada, Kohei Kaiya, Yusuke Nago, Satoshi Murakawa, and Keiya Shirahama

    [International presentation]  30th International Conference on Low Temperature Physics(LT30) (Bilbao Exhibition Centre) , 

    2025.08
    , 

    Poster presentation

  • Freezing of surface TLS-induced electric dipoles by helium adsorption

    Kohei Okamura, Ryuku Iwama, Yusuke Nago, and Keiya Shirahama

    [International presentation]  30th International Conference on Low Temperature Physics(LT30) (Bilbao Exhibition Centre) , 

    2025.08
    , 

    Poster presentation

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Research Projects of Competitive Funds, etc. 【 Display / hide 】

  • 超流動流が誘起する揚力と量子化循環生成の検証

    2026.04
    -
    2029.03

    Research grant, Principal investigator

  • 液体ヘリウムにおける超高速超流動の実現と速度誘起超固体転移の探索

    2024.04
    -
    2027.03

    Research grant, Coinvestigator(s)

  • 液体ヘリウム3における近藤効果の探索

    2023.04
    -
    2025.03

    Research grant, Coinvestigator(s)

  • Nonlinear wave phenomena excited on vortex lines in quantum turbulence

    2022.04
    -
    2026.03

    MEXT,JSPS, Grant-in-Aid for Scientific Research, 基盤研究(C), Principal investigator

  • Novel Quantum Phenomena in 2D Helium with Aspects of Quantum Phase Transition

    2020.04
    -
    2023.03

    Keio University, Grant-in-Aid for Scientific Research (A), No Setting

    　View Summary

    ヘリウム薄膜は「2次元強相関量子多体系」として、トポロジカル超流動、量子液晶、非平衡などの新現象を示しうる。申請者は2次元ヘリウムの性質が「励起にエネルギーギャップをもつ局在固体」と「超流動」間の「量子相転移」という見方―量子相転移描像―で統一的に理解できることを提案している。
    本研究ではこの量子相転移描像に基づき、2次元ヘリウムに期待される新奇量子現象を開拓する。具体的には、(1)フォノン照射による非平衡超流動状態の実現、(2)純2次元トポロジカル超流動ヘリウム3の探索、(3)ヘリウム4薄膜における固体と超流動の共存の検証、という3つの新奇量子凝縮相・量子現象の解明に取り組む。

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Awards 【 Display / hide 】

  • 領域6若手奨励賞受賞

    永合 祐輔, 2018.03, 日本物理学会, 超流動ヘリウムにおける量子渦・量子乱流発生機構の実験的解明

    Type of Award： Award from Japanese society, conference, symposium, etc.

  • 第10回低温工学・超伝導若手合同講演会信貴賞

    永合祐輔, 2011.12, 低温工学協会, 超微細超伝導線振動子による超流動ヘリウム中の量子渦検出

    Type of Award： Award from Japanese society, conference, symposium, etc.

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Other 【 Display / hide 】

  • 振動物体を用いた超流動ヘリウム中量子渦・量子乱流生成

    2017年12月

    　View Details

    大阪市立大学　2017年度 物理教室年末研究発表会　招待講演

  • Transition to Turbulence Generated by a Vibrating Wire in 3He – B phase

    2008年04月

    　View Details

    ヘルシンキ工科大学(現アールト大学)低温物性グループセミナー　口頭発表

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Courses Taught 【 Display / hide 】

  • PHYSICS LABORATORIES 2

    2026

  • LABORATORIES IN SCIENCE AND TECHNOLOGY

    2026

  • PHYSICS SEMINAR 2

    2026

  • LABORATORY IN SCIENCE

    2026

  • PHYSICS LABORATORIES 1

    2026

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Courses Previously Taught 【 Display / hide 】

  • 物理学セミナー第4

    Keio University

    2022.04
    -
    2023.03
    , 

    Autumn Semester, Undergraduate (specialized), Seminar, Within own ｆaculty, 2h, 9people

  • 理工学基礎実験

    Keio University

    2019.04
    -
    2025.03
    , 

    Autumn Semester, Undergraduate (specialized), Laboratory work/practical work/exercise, Within own ｆaculty, 3h

  • 物理学実験第１

    Keio University

    2018.04
    -
    2025.03
    , 

    Spring Semester, Laboratory work/practical work/exercise, Within own ｆaculty, 6h

  • 物理学実験第２

    Keio University

    2018.04
    -
    2025.03
    , 

    Autumn Semester, Laboratory work/practical work/exercise, Within own ｆaculty, 6h

  • 自然科学実験

    Keio University

    2018.04
    -
    2025.03
    , 

    Spring Semester, Laboratory work/practical work/exercise, Within own ｆaculty, 3h

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Social Activities 【 Display / hide 】

  • 絶対零度の世界～超伝導の不思議～

    慶應義塾大学, 2023年度 塾内高校生のための夏休み研究体験 (慶應義塾大学矢上キャンパス)

    , 
    2023.08

  • 絶対零度の世界～超伝導の不思議～

    慶應義塾大学, 2019年度 塾内高校生のための夏休み研究体験　 (慶應義塾大学矢上キャンパス)

    , 
    2019.08

  • 超低温物理の世界：超流動と超伝導

    慶應義塾大学, 慶應義塾大学オープンキャンパス 一般向け講演 学問のすゝめ (慶應義塾大学矢上キャンパス)

    , 
    2016.08
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Memberships in Academic Societies 【 Display / hide 】

  • 公益社団法人　応用物理学会, 

    2014.02
    -
    Present

  • 一般社団法人　日本物理学会, 

    2006.01
    -
    Present
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Committee Experiences 【 Display / hide 】

  • 2019.10
    -
    2020.09

    日本物理学会領域6運営委員

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