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BCS-BECクロスオーバー領域におけるフェルミ超流体の熱力学と超流動物性

Publicly Offered Research

Project AreaNuclear matter in neutron stars investigated by experiments and astronomical observations
Project/Area Number 25105511
Research Category

Grant-in-Aid for Scientific Research on Innovative Areas (Research in a proposed research area)

Allocation TypeSingle-year Grants
Review Section Science and Engineering
Research InstitutionKeio University

Principal Investigator

大橋 洋士  慶應義塾大学, 理工学部, 教授 (60272134)

Project Period (FY) 2013-04-01 – 2015-03-31
Project Status Completed (Fiscal Year 2014)
Budget Amount *help
¥2,340,000 (Direct Cost: ¥1,800,000、Indirect Cost: ¥540,000)
Fiscal Year 2014: ¥1,170,000 (Direct Cost: ¥900,000、Indirect Cost: ¥270,000)
Fiscal Year 2013: ¥1,170,000 (Direct Cost: ¥900,000、Indirect Cost: ¥270,000)
Keywordsフェルミ原子気体 / BCS-BECクロスオーバー / 擬ギャップ / スピン帯磁率 / 比熱 / スピンギャップ / 圧縮率
Outline of Annual Research Achievements

本年度は、前年度構築した、正常相におけるフェルミ原子気体のスピン帯磁率に対する「拡張されたT行列理論」を、超流動転移温度以下の領域に拡張、BCS-BECクロスオーバー全領域の超流動相におけるこの物理量の振る舞いを明らかにした。BCS-BECクロスオーバー領域の正常相では、クーパー対分子の形成に伴ってスピン帯磁率が抑制されるが、超流動転移温度以下では、逆に超流動揺らぎに伴うクーパー対の解離により、スピン帯磁率の抑制が緩和されることを示した。また、その温度変化の詳細な解析により、そうした効果が見られる温度領域の特定を行った。
本年度は更に、比熱に対する強結合補正も研究した。ユニタリ極限近傍では、強い超流動揺らぎにより、超流動転移温度近傍の比熱が非常にエンハンスされることを、ガウス揺らぎの理論に基づいて数値的に明らかにした。また、超流動転移温度以上での比熱の温度変化の解析から、理想分子ボーズ気体とみなせる領域を特定することに成功、これまで知られていた擬ギャップ温度に加え、分子ボーズ気体の領域と、フェルミ原子と分子ボソンが共存する領域を分ける新しい「特徴的温度」が存在することを見出した。
また、これまでの3次元系に対する理論を2次元フェルミ原子気体に適用できるように拡張、近年観測が報告されたBKT転移を研究した。強結合T行列理論の枠組みで、重心運動量ゼロのクーパー対分子数の温度依存性をBKT転移温度以上で計算、BKT転移の実験的根拠とされたこの物理量の増大が、BKT転移を仮定しなくても強い超流動揺らぎだけで説明できることを明らかにした。この結果に基づき、実験は必ずしもBKT転移を観測したとは断定できないことを指摘した。

Research Progress Status

26年度が最終年度であるため、記入しない。

Strategy for Future Research Activity

26年度が最終年度であるため、記入しない。

Report

(2 results)
  • 2014 Annual Research Report
  • 2013 Annual Research Report
  • Research Products

    (37 results)

All 2015 2014 2013

All Journal Article (9 results) (of which Peer Reviewed: 9 results,  Acknowledgement Compliant: 5 results,  Open Access: 3 results) Presentation (28 results) (of which Invited: 2 results)

  • [Journal Article] Heteropairing and component-dependent pseudogap phenomena in an ultracold Fermi gas with different species with different masses2014

    • Author(s)
      R. Hanai, and Y. Ohashi
    • Journal Title

      Phys. Rev. A

      Volume: 90 Issue: 4

    • DOI

      10.1103/physreva.90.043622

    • Related Report
      2014 Annual Research Report
    • Peer Reviewed / Acknowledgement Compliant
  • [Journal Article] Green’s-function formalism for a condensed Bose gas consistent with infrared-divergent longitudinal susceptibility and Nepomnyashchii-Nepomnyashchii identity2014

    • Author(s)
      S. Watabe, and Y. Ohashi
    • Journal Title

      Phys. Rev. A

      Volume: 90 Issue: 1

    • DOI

      10.1103/physreva.90.013603

    • Related Report
      2014 Annual Research Report
    • Peer Reviewed / Acknowledgement Compliant
  • [Journal Article] Spin-gap phenomenon in a strongly interacting ultracold Fermi gas2014

    • Author(s)
      H. Tajima, R. Hanai, and Y. Ohashi
    • Journal Title

      J. Phys. Conf. Series

      Volume: 568 Issue: 1 Pages: 012019-012019

    • DOI

      10.1088/1742-6596/568/1/012019

    • Related Report
      2014 Annual Research Report
    • Peer Reviewed / Open Access / Acknowledgement Compliant
  • [Journal Article] Hetero-pairing and pseudogap phenomena in an ultracold Fermi gas with mass imbalance2014

    • Author(s)
      R. Hanai, and Y. Ohashi
    • Journal Title

      J. Phys. Conf. Series

      Volume: 568 Issue: 1 Pages: 012004-012004

    • DOI

      10.1088/1742-6596/568/1/012004

    • Related Report
      2014 Annual Research Report
    • Peer Reviewed / Open Access / Acknowledgement Compliant
  • [Journal Article] Pseudogap phenomena in a two-dimensional ultracold Fermi gas near the Berezinskii-Kosterlitz-Thouless transition2014

    • Author(s)
      M. Matsumoto, and Y. Ohashi
    • Journal Title

      J. Phys. Conf. Series

      Volume: 568 Issue: 1 Pages: 012012-012012

    • DOI

      10.1088/1742-6596/568/1/012012

    • Related Report
      2014 Annual Research Report
    • Peer Reviewed / Open Access / Acknowledgement Compliant
  • [Journal Article] Pseudogap phenomenon and effects of population imbalanace in the normal state of a unitary Fermi gas2014

    • Author(s)
      T,Kashimura, R.Watanabe, Y.Ohashi
    • Journal Title

      Physical Review A

      Volume: 89 Issue: 1

    • DOI

      10.1103/physreva.89.013618

    • Related Report
      2013 Annual Research Report
    • Peer Reviewed
  • [Journal Article] Uniform spin susceptibility and spin-gap phenomenon in the BCS-BEC crossover regime of an ultracold Fermi gas2014

    • Author(s)
      H.Tajima, T.Kashimura, R.Hanai, R.Watanabe, Y.Ohashi
    • Journal Title

      Physical Review A

      Volume: 89 Issue: 3

    • DOI

      10.1103/physreva.89.033617

    • Related Report
      2013 Annual Research Report
    • Peer Reviewed
  • [Journal Article] Spin-gap temperature in the BCS-BEC crossover regime of an ultracold Fermi gas2014

    • Author(s)
      H.Tajima, T.Kashimura, R.Hanai, R.Watanabe, Y.Ohashi
    • Journal Title

      JPS Conference Proceedings

      Volume: 1

    • DOI

      10.7566/jpscp.1.012096

    • Related Report
      2013 Annual Research Report
    • Peer Reviewed
  • [Journal Article] Unconventional triplet pairing and effects of Fermi surface deformation in a gas of polarized dipolar Fermi molecules2014

    • Author(s)
      Y.Endo,D.Inotani,Y.Ohashi
    • Journal Title

      JPS Conference Proceedings

      Volume: 1

    • DOI

      10.7566/jpscp.1.012095

    • Related Report
      2013 Annual Research Report
    • Peer Reviewed
  • [Presentation] フェルミ原子気体のBCS-BECクロスオーバー領域における粘性率2015

    • Author(s)
      鏡原大地、大橋洋士
    • Organizer
      日本物理学会年会
    • Place of Presentation
      早稲田大学 (東京都・新宿区)
    • Year and Date
      2015-03-22
    • Related Report
      2014 Annual Research Report
  • [Presentation] 2次元Fermi原子ガスのBKT転移近傍における強結合効果2015

    • Author(s)
      松本杜青、大橋洋士
    • Organizer
      日本物理学会年会
    • Place of Presentation
      早稲田大学 (東京都・新宿区)
    • Year and Date
      2015-03-22
    • Related Report
      2014 Annual Research Report
  • [Presentation] フェルミ原子気体超流動のスピン帯磁率に現れる超流動秩序と対破壊揺らぎの競合Ⅱ2015

    • Author(s)
      田島裕之、花井亮、大橋洋士
    • Organizer
      日本物理学会年会
    • Place of Presentation
      早稲田大学 (東京都・新宿区)
    • Year and Date
      2015-03-22
    • Related Report
      2014 Annual Research Report
  • [Presentation] Specific Heat and Effects of Pairing Fluctuations in an ultracold Fermi gas in the BCS-BEC crossover region2015

    • Author(s)
      Pieter van Wyk, Hiroyuki Tajima, Ryo Hanai, and Yoji Ohashi
    • Organizer
      日本物理学会年会
    • Place of Presentation
      早稲田大学 (東京都・新宿区)
    • Year and Date
      2015-03-21
    • Related Report
      2014 Annual Research Report
  • [Presentation] フェルミ原子気体のBCS-BEC クロスオーバー領域における比熱2015

    • Author(s)
      大橋洋士, Pieter van Wyk
    • Organizer
      新学術領域「実験と観測で解き明かす中性子星の核物質」研究会
    • Place of Presentation
      京都大学基礎物理学研究所 (京都府・京都市)
    • Year and Date
      2015-03-12
    • Related Report
      2014 Annual Research Report
  • [Presentation] Hetero-pairing and pseudogap phenomenon in the BCS-BEC crossover regime of an ultracold Fermi gas with mass imbalance2014

    • Author(s)
      Yoji Ohashi, and Ryo Hanai
    • Organizer
      International workshop on "Probing and Understanding of exotic superconductivity and superfluids"
    • Place of Presentation
      Trieste (Italy)
    • Year and Date
      2014-10-27
    • Related Report
      2014 Annual Research Report
    • Invited
  • [Presentation] フェルミ原子ガス超流動のBCS-BEC クロスオーバー領域における超流動秩序と超流動揺らぎの競合2014

    • Author(s)
      大橋洋士, 田島祐之, 花井亮, Pieter van Wyk
    • Organizer
      新学術領域「実験と観測で解き明かす中性子星の核物質」研究会
    • Place of Presentation
      熱川温泉、熱川ハイツ (静岡県・賀茂郡)
    • Year and Date
      2014-09-24
    • Related Report
      2014 Annual Research Report
  • [Presentation] フェルミ原子気体超流動のスピン帯磁率に現れる超流動秩序と対破壊揺らぎの競合2014

    • Author(s)
      田島祐之、花井亮、大橋洋士
    • Organizer
      日本物理学会
    • Place of Presentation
      中部大学 (愛知県・春日井市)
    • Year and Date
      2014-09-07
    • Related Report
      2014 Annual Research Report
  • [Presentation] Strong-coupling corrections to the specific heat of an ultracold Fermi gas in the BCS-BEC crossover region2014

    • Author(s)
      Pieter van Wyk, Hiroyuki Tajima, Ryo Hanai, and Yoji Ohashi
    • Organizer
      日本物理学会
    • Place of Presentation
      中部大学 (愛知県・春日井市)
    • Year and Date
      2014-09-07
    • Related Report
      2014 Annual Research Report
  • [Presentation] 6Li-40K混合系におけるヘテロクーパー対形成と強結合補正2014

    • Author(s)
      花井亮、大橋洋士
    • Organizer
      日本物理学会
    • Place of Presentation
      中部大学 (愛知県・春日井市)
    • Year and Date
      2014-09-07
    • Related Report
      2014 Annual Research Report
  • [Presentation] 2次元フェルミ原子ガスのBKT転移と励起スペクトル2014

    • Author(s)
      松本杜青、大橋洋士
    • Organizer
      日本物理学会
    • Place of Presentation
      中部大学 (愛知県・春日井市)
    • Year and Date
      2014-09-07
    • Related Report
      2014 Annual Research Report
  • [Presentation] 強結合フェルミ超流動体のスピン帯磁率における超流動揺らぎと秩序の競合現象2014

    • Author(s)
      田島裕之、大橋洋士
    • Organizer
      熱場の量子論とその応用
    • Place of Presentation
      理化学研究所 (埼玉県・和光市)
    • Year and Date
      2014-09-04
    • Related Report
      2014 Annual Research Report
  • [Presentation] 流入と散逸のあるフェルミ粒子系における非平衡強結合効果2014

    • Author(s)
      花井亮、大橋洋士
    • Organizer
      熱場の量子論とその応用
    • Place of Presentation
      理化学研究所 (埼玉県・和光市)
    • Year and Date
      2014-09-04
    • Related Report
      2014 Annual Research Report
  • [Presentation] Specific heat and strong-coupling effects in the BCS-BEC crossover regime of an ultracold Fermi gas2014

    • Author(s)
      Pieter van Wyk, Hiroyuki Tajima, Ryo Hanai, and Yoji Ohashi
    • Organizer
      熱場の量子論とその応用
    • Place of Presentation
      理化学研究所 (埼玉県・和光市)
    • Year and Date
      2014-09-04
    • Related Report
      2014 Annual Research Report
  • [Presentation] Pseudogap phenomena in a two-dimensional ultracold Fermi gas near the Berezinskii-Kosterlitz-Thouless transition2014

    • Author(s)
      Morio Matsumoto, and Yoji Ohashi
    • Organizer
      27th International Conference on Low Temperature Physics (LT27)
    • Place of Presentation
      Buenos Aires (Argentina)
    • Year and Date
      2014-08-08
    • Related Report
      2014 Annual Research Report
  • [Presentation] Hetero-pairing and pseudogap phenomena in an ultracold Fermi gas with mass imbalance2014

    • Author(s)
      Ryo Hanai, and Yoji Ohashi
    • Organizer
      27th International Conference on Low Temperature Physics (LT27)
    • Place of Presentation
      Buenos Aires (Argentina)
    • Year and Date
      2014-08-08
    • Related Report
      2014 Annual Research Report
  • [Presentation] Spin gap phenomenon in a strongly interacting ultracold Fermi gas2014

    • Author(s)
      Hiroyuki Tajima, Ryo Hanai, and Yoji Ohashi
    • Organizer
      27th International Conference on Low Temperature Physics (LT27)
    • Place of Presentation
      Buenos Aires (Argentina)
    • Year and Date
      2014-08-08
    • Related Report
      2014 Annual Research Report
  • [Presentation] Spin-gap phenomena and pseudogap effects in a strongly interacting ultracold Fermi gas2014

    • Author(s)
      Yoji Ohashi, and Hiroyuki Tajima
    • Organizer
      International Workshop, "Intersection of cold-atomic and nuclear physics"
    • Place of Presentation
      Pohang (Korea)
    • Year and Date
      2014-05-13
    • Related Report
      2014 Annual Research Report
    • Invited
  • [Presentation] Magnetic excitations and spin-gap phenomenon in the BCS-BEC crossover regime of an ultracold Fermi gas2014

    • Author(s)
      Hiroyuki Tajima, Takashi Kashimura, Ryo Hanai, Ryota Watanabe, and Yoji Ohashi
    • Organizer
      APS March Meeting
    • Place of Presentation
      Denver, Colorado, US
    • Related Report
      2013 Annual Research Report
  • [Presentation] Collective properties of two-dimensional Dirac electron system with a superconducting pairing interaction2014

    • Author(s)
      Daisuke Inotani, Yoji Ohashi, Susumu Okada
    • Organizer
      APS March Meeting
    • Place of Presentation
      Denver, Colorado, US
    • Related Report
      2013 Annual Research Report
  • [Presentation] 2次元ディラック電子系における超伝導状態での集団励起II2014

    • Author(s)
      猪谷太輔,大橋洋士、岡田晋
    • Organizer
      日本物理学会
    • Place of Presentation
      東海大学
    • Related Report
      2013 Annual Research Report
  • [Presentation] Unconventional triplet pairing and effects of Fermi surface deformation in a gas of polarized dipolar Fermi molecules2013

    • Author(s)
      Yuki Endo, Daisuke Inotani, Yoji Ohashi
    • Organizer
      The 12th Asia Pacific Physics Conference (APPC12)
    • Place of Presentation
      International conference hall, Makuhari Messe, Japan
    • Related Report
      2013 Annual Research Report
  • [Presentation] Spin gap temperature in the BCS-BEC crossover regime of an ultracold Fermi gas2013

    • Author(s)
      Hiroyuki Tajima, Takashi Kashimura, Ryo Hanai, Ryota Watanabe, Yoji Ohashi
    • Organizer
      The 12th Asia Pacific Physics Conference (APPC12)
    • Place of Presentation
      International conference hall, Makuhari Messe, Japan
    • Related Report
      2013 Annual Research Report
  • [Presentation] Superfluid theory of a gas of polarized dipolar Fermi molecules2013

    • Author(s)
      Yuki Endo, Daisuke Inotani, Yoji Ohashi
    • Organizer
      International Symposium on Quantum Fluids and Solids (QFS2013)
    • Place of Presentation
      Kunibiki Messe, Matsue, Japan
    • Related Report
      2013 Annual Research Report
  • [Presentation] Spin Susceptibility and Strong Coupling Effects in an Ultracold Fermi Gas2013

    • Author(s)
      Hiroyuki Tajima, Ryo Hanai, Ryota Watanabe, Yoji Ohashi
    • Organizer
      International Symposium on Quantum Fluids and Solids (QFS2013)
    • Place of Presentation
      Kunibiki Messe, Matsue, Japan
    • Related Report
      2013 Annual Research Report
  • [Presentation] BCS-BECクロスオーバー領域におけるフェルミ超流体の熱力学と超流動物性2013

    • Author(s)
      大橋洋士
    • Organizer
      新学術領域「実験と観測で解き明かす中性子星の核物質(中性子核物質)」公募研究交流会
    • Place of Presentation
      東北大学理学部
    • Related Report
      2013 Annual Research Report
  • [Presentation] 冷却フェルミ原子ガスのBCS-BECクロスオーバーにおけるスピンギャップ現象の解析2013

    • Author(s)
      田島祐之、花井亮、渡邉亮太、大橋洋士
    • Organizer
      日本物理学会
    • Place of Presentation
      徳島大学
    • Related Report
      2013 Annual Research Report
  • [Presentation] 2次元ディラック電子系における超伝導状態での集団励起2013

    • Author(s)
      猪谷太輔,大橋洋士、岡田晋
    • Organizer
      日本物理学会
    • Place of Presentation
      徳島大学
    • Related Report
      2013 Annual Research Report

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Published: 2013-05-15   Modified: 2019-07-29  

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