Updated on 2025/03/25

写真a

 
FURUTANI Koichiro
 
Organization
Institute for Advanced Research Designated assistant professor
Graduate School of Engineering Designated assistant professor
Title
Designated assistant professor

Degree 1

  1. Ph.D. ( 2024.2   University of Padova ) 

 

Papers 12

  1. Predictive power of the Berezinskii-Kosterlitz-Thouless theory based on renormalization group throughout the BCS-BEC crossover in two-dimensional superconductors

    Midei, G; Furutani, K; Salasnich, L; Perali, A

    PHYSICAL REVIEW B   Vol. 110 ( 21 )   2024.12

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    Publisher:Physical Review B  

    Recent experiments on 2D superconductors allow the characterization of the critical temperature and of the phase diagram across the BCS-BEC crossover as a function of density. We obtain from these experiments the microscopic parameters of the superconducting state at low temperatures by the BCS mean-field approach. For LixZrNCl, the extracted parameters are used to evaluate the superconducting phase stiffness and the Berezinskii-Kosterlitz-Thouless (BKT) critical temperature throughout the BCS-BEC crossover by implementing the corresponding renormalization group (RG) approach. In this way, we make a quantitative test of the predictive power of the BKT theory for evaluating the critical temperature. The RG flow equations turn out to give a sizable renormalization of the phase stiffness and of the critical temperature, which is crucial to obtain a satisfactory agreement between the BKT theory and the experiments, in particular, in the BCS-BEC crossover regime. We predict the temperature range where phase stiffness renormalization can be measured in LixZrNCl across the BCS-BEC crossover. Contrary to other microscopic theories of superconductivity, we find that the BKT theory can be exploited to evaluate quantitatively the critical temperature of 2D superconductors in different pairing regimes.

    DOI: 10.1103/PhysRevB.110.214502

    Web of Science

    Scopus

  2. Interaction-induced dissipative quantum phase transition in a head-to-tail atomic Josephson junction Reviewed International coauthorship

    Koichiro Furutani, Luca Salasnich

    Physical Review B     2024.10

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    Authorship:Lead author, Corresponding author   Language:English   Publishing type:Research paper (scientific journal)  

    DOI: https://doi.org/10.1103/PhysRevB.110.L140503

    DOI: 10.1103/PhysRevB.110.L140503

  3. Amplitude, phase, and topological fluctuations shaping the complex phase diagram of two-dimensional superconductors Reviewed International coauthorship

    Koichiro Furutani, Giovanni Midei, Andrea Perali, Luca Salasnich

    Physical Review B   ( 110 )   2024.10

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    Authorship:Lead author, Corresponding author   Language:English   Publishing type:Research paper (scientific journal)  

    DOI: https://doi.org/10.1103/PhysRevB.110.134501

    DOI: 10.1103/PhysRevB.110.134501

  4. Fokker-Planck equations for a trapped particle in a quantum-thermal Ohmic bath: general theory and applications to Josephson junctions Invited Reviewed International coauthorship

    Koichiro Furutani, Luca Salasnich

    AAPPS Bulletin   ( 33 )   2023.9

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    Authorship:Lead author, Corresponding author   Language:English   Publishing type:Research paper (scientific journal)  

    DOI: https://doi.org/10.1007/s43673-023-00087-2

    DOI: 10.1007/s43673-023-00087-2

  5. Berezinskii-Kosterlitz-Thouless phase transition with Rabi-coupled bosons Reviewed International coauthorship

    Koichiro Furutani, Andrea Perali, Luca Salasnich

    Physical Review A   ( 107 )   2023.4

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    Authorship:Lead author, Corresponding author   Language:English   Publishing type:Research paper (scientific journal)  

    DOI: https://doi.org/10.1103/PhysRevA.107.L041302

    DOI: 10.1103/PhysRevA.107.L041302

  6. First and Second Sound in Two-Dimensional Bosonic and Fermionic Superfluids Invited Reviewed International coauthorship

    L. Salasnich, A. Cappellaro, K. Furutani, A. Tononi, G. Bighin

    Symmetry   ( 14 )   2022.10

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    Language:English   Publishing type:Research paper (scientific journal)  

    DOI: https://doi.org/10.3390/sym14102182

    DOI: 10.3390/sym14102182

  7. Quantum effective action for the bosonic Josephson junction Reviewed International coauthorship

    Koichiro Furutani, Jacques Tempere, Luca Salasnich

    Physical Review B   ( 105 )   2022.4

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    Authorship:Lead author, Corresponding author   Language:English   Publishing type:Research paper (scientific journal)  

    DOI: https://doi.org/10.1103/PhysRevB.105.134510

    DOI: 10.1103/PhysRevB.105.134510

  8. Superfluid properties of bright solitons in a ring Reviewed International coauthorship

    Koichiro Furutani, Luca Salasnich

    Physical Review A   ( 105 )   2022.3

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    Authorship:Lead author, Corresponding author   Language:English   Publishing type:Research paper (scientific journal)  

    DOI: https://doi.org/10.1103/PhysRevA.105.033320

    DOI: 10.1103/PhysRevA.105.033320

  9. Quantum and thermal fluctuations in the dynamics of a resistively and capacitively shunted Josephson junction Reviewed International coauthorship

    Koichiro Furutani, Luca Salasnich

    Physical Review B   ( 104 )   2021.7

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    Authorship:Lead author, Corresponding author   Language:English   Publishing type:Research paper (scientific journal)  

    DOI: https://doi.org/10.1103/PhysRevB.104.014519

    DOI: 10.1103/PhysRevB.104.014519

  10. Dissipation and fluctuations in elongated bosonic Josephson junctions Reviewed International coauthorship

    Francesco Binanti, Koichiro Furutani, Luca Salasnich

    Physical Review A   ( 103 )   2021.6

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    Language:English   Publishing type:Research paper (scientific journal)  

    DOI: https://doi.org/10.1103/PhysRevA.103.063309

    DOI: 10.1103/PhysRevA.103.063309

  11. Sound modes in collisional superfluid Bose gases Reviewed International coauthorship

    Koichiro Furutani, Andrea Tononi, Luca Salasnich

    New Journal of Physics   ( 23 )   2021.4

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    Authorship:Lead author, Corresponding author   Language:English   Publishing type:Research paper (scientific journal)  

    DOI: https://doi.org/10.1088/1367-2630/abed0c

    DOI: 10.1088/1367-2630/abed0c

  12. Strong-coupling Effects on Quantum Transport in an Ultracold Fermi Gas Reviewed

    Koichiro Furutani, Yoji Ohashi

    Journal of Low Temperature Physics   ( 201 ) page: 49 - 57   2020.6

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    Authorship:Lead author, Corresponding author   Language:English   Publishing type:Research paper (international conference proceedings)  

    DOI: https://doi.org/10.1007/s10909-020-02482-7

    DOI: 10.1007/s10909-020-02482-7

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Presentations 4

  1. Dissipative quantum phase transition in a head-to-tail atomic Josephson junction International conference

    Koichiro Furutani

    APS Global Physics Summit  2025.3.19 

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    Event date: 2025.3

    Language:English   Presentation type:Oral presentation (general)  

    Venue:Anaheim   Country:United States  

  2. Dissipative dynamics and quantum phase transition in an atomic Josephson junction Invited

    Koichiro Furutani

    Seminar (Condensed Matter Theory Group, University of Padova)  2024.11.26 

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    Event date: 2024.11

    Language:English   Presentation type:Public lecture, seminar, tutorial, course, or other speech  

    Venue:Padova   Country:Italy  

  3. Berezinskii-Kosterlitz-Thouless transition in a two-dimensional binary Bose mixture Invited International conference

    Koichiro Furutani

    SuperFluctuations2024  2024.9.18 

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    Event date: 2024.9

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

    Venue:Salerno   Country:Italy  

  4. Berezinskii-Kosterlitz-Thouless transition in a Rabi-coupled binary Bose superfluid Invited International conference

    Koichiro Furutani

    Ultracold Atoms Japan 2024  2024.4.9 

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    Event date: 2024.4

    Language:English   Presentation type:Oral presentation (general)  

    Venue:Okinawa   Country:Japan  

Research Project for Joint Research, Competitive Funding, etc. 1

  1. 機械学習を用いた多成分量子多体系におけるトポロジカル相転移の解析

    2024.6 - 2025.3

    牧誠記念研究助成 

    古谷浩一朗

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    Authorship:Principal investigator  Grant type:Competitive

    Grant amount:\1000000

KAKENHI (Grants-in-Aid for Scientific Research) 1

  1. スピノル超流動を用いた多成分量子多体系の量子相制御

    Grant number:24K22858  2024.7 - 2026.3

    科学研究費助成事業  研究活動スタート支援

    古谷 浩一朗

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    Authorship:Principal investigator 

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

    原子種やスピンといった多自由度によって実現する多成分量子多体系の静的・動的制御手法を理論的に開拓する。多成分系では、その自由度のため単成分系よりも多彩なトポロジカル励起が現れ、相転移や動的応答といったマクロな物理現象に新たな可能性を拓くが、その系統的理解は未だ得られていない。その包括的解明のため、本研究では操作性の高い冷却原子系を舞台とし、スピン自由度を持った超流動に現れるトポロジカル励起の代数構造の観点から、多成分量子系における相転移や動的応答の新奇な物理的性質とその制御手法を探索する。