極低温フェルミ原子気体における状態方程式の理論的決定と中性子星低密度領域への応用

• Project Area: Nuclear matter in neutron stars investigated by experiments and astronomical observations
• Project/Area Number: 15H00840
• Research Category: Grant-in-Aid for Scientific Research on Innovative Areas (Research in a proposed research area)
• Allocation Type: Single-year Grants
• Review Section: Science and Engineering
• Research Institution: Keio University
• Principal Investigator: 大橋 洋士 慶應義塾大学, 理工学部(矢上), 教授 (60272134)
• Project Period (FY): 2015-04-01 – 2017-03-31
• Project Status: Completed (Fiscal Year 2016)
• Budget Amount: ¥2,600,000 (Direct Cost: ¥2,000,000、Indirect Cost: ¥600,000); Fiscal Year 2016: ¥1,300,000 (Direct Cost: ¥1,000,000、Indirect Cost: ¥300,000); Fiscal Year 2015: ¥1,300,000 (Direct Cost: ¥1,000,000、Indirect Cost: ¥300,000)
• Keywords: フェルミ原子気体 / 超流動 / 中性子星 / 状態方程式 / 有効距離 / ユニタリ領域 / ＢＣＳ－ＢＥＣクロスオーバー / 強結合効果 / BCS-BECクロスオーバー / 比熱 / ユニタリ極限

Outline of Annual Research Achievements

昨年度、NozieresとSchmitt-RinkによるBCS-BECクロスオーバーの理論をユニタリ領域にあるフェルミ原子ガス超流動に拡張、この領域で観測された内部エネルギーを理論的に再現することに成功したが、今年度は、これをｓ波超流動状態にあるとされる中性子星の低密度領域に拡張することを行った。冷却フェルミ原子ガスに対する研究では必要なかった有効距離（effective range: r）の効果を理論に追加し、中性子星での値r=2.7 fmの影響を取り扱えるようにした。更に、それに伴い発生するHartreeエネルギーの効果も取り扱えるよう、理論を発展させた。
有効距離の効果のみを考慮した場合、中性子星の内部に進み密度が上昇するとフェルミ波数が大きくなり、その値が有効距離の逆数程度に達するとCooper対形成に対する引力相互作用の効果が抑制されるため、凝縮エネルギーが減少、結果、内部エネルギーは上昇する。一方、密度の上昇はHartreeエネルギーを上昇させ、これは内部エネルギーを減少させる。この相反する２つの効果が合わさった結果、計算された内部エネルギーは飽和核密度近傍まで既存の計算結果を良く再現することを見出した。既存の結果がAV18などのように非常に多くの実験パラメータを必要としているのに対し、今回の結果は、ｓ波相互作用に対する散乱長と有効距離しか必要としておらず、この単純さは今後理論を中性子星の更なる内深部へ拡張する際に非常に有利であると考えられる。
上記に加え、近年、カリウム40フェルミ原子気体のユニタリ領域で観測された局所光原子分光スペクトルに対する理論研究も行い、この領域で重要となる超流動揺らぎの効果を取り入れることで、フィッティングパラメータを一切用いることなく、実験結果を説明することに成功した。

Research Progress Status

28年度が最終年度であるため、記入しない。

Strategy for Future Research Activity

28年度が最終年度であるため、記入しない。

Research Products

• [Journal Article] Strong-Coupling Properties of a p-Wave Interacting Fermi Gas on the Viewpoint of Specific Heat at Constant Volume (2017)
  • Author(s): Daisuke Inotani, Pieter van Wyk, and Yoji Ohashi
  • Journal Title: Journal of the Physical Society of Japan Volume: 86 Issue: 2 Pages: 024302-024302
  • DOI: 10.7566/jpsj.86.024302
  • Peer Reviewed / Acknowledgement Compliant
• [Journal Article] Specific Heat and Effects of Uniaxial Anisotropy of a p-Wave Pairing Interaction in a Strongly Interacting Ultracold Fermi Gas (2017)
  • Author(s): Daisuke Inotani, Pieter van Wyk, and Yoji Ohashi
  • Journal Title: Journal of the Physical Society of Japan Volume: 86 Issue: 4 Pages: 044301-044301
  • DOI: 10.7566/jpsj.86.044301
  • Peer Reviewed / Acknowledgement Compliant
• [Journal Article] A Novel Route to Reach a p-Wave Superfluid Fermi Gas (2017)
  • Author(s): Tokitake Yamaguchi, Daisuke Inotani, and Yoji Ohashi
  • Journal Title: Journal of the Physical Society of Japan Volume: 86 Issue: 1 Pages: 013001-013001
  • DOI: 10.7566/jpsj.86.013001
  • Peer Reviewed / Acknowledgement Compliant
• [Journal Article] フェルミ原子ガス超流動のＢＣＳ－ＢＥＣクロスオーバー理論と中性子星状態方程式への挑戦 (2016)
  • Author(s): 大橋洋士, Pieter van Wyk, 田島裕之
  • Journal Title: 原子核研究 Volume: 61 Pages: 70-84
  • Peer Reviewed / Acknowledgement Compliant
• [Journal Article] Triplet pair amplitude in a trapped s-wave superfluid Fermi gas with broken spin rotation symmetry. II. Three-dimensional continuum case (2016)
  • Author(s): Daisuke Inotani, Ryo Hanai, and Yoji Ohashi
  • Journal Title: Physical Review A Volume: 94 Issue: 4 Pages: 043632-043632
  • DOI: 10.1103/physreva.94.043632
  • Peer Reviewed / Acknowledgement Compliant
• [Journal Article] Dip-Hump Temperature Dependence of Specific Heat and Effects of Pairing Fluctuations in the Weak-Coupling Side of a P-Wave Interacting Fermi Gas (2016)
  • Author(s): Daisuke Inotani, Pieter van Wyk, and Yoji Ohashi
  • Journal Title: Journal of the Physical Society of Japan Volume: 85 Issue: 12 Pages: 123301-123301
  • DOI: 10.7566/jpsj.85.123301
  • Peer Reviewed / Acknowledgement Compliant
• [Journal Article] Specific heat and effects of pairing fluctuations in the BCS-BEC-crossover regime of an ultracold Fermi gas (2016)
  • Author(s): Pieter van Wyk, Hiroyuki Tajima, Ryo Hanai, and Yoji Ohashi
  • Journal Title: Physical Review A Volume: 93 Issue: 1
  • DOI: 10.1103/physreva.93.013621
  • Peer Reviewed / Acknowledgement Compliant
• [Journal Article] Cooper pairs with zero center-of-mass momentum and their first-order correlation function in a two-dimensional ultracold Fermi gas near a Berezinskii-Kosterlitz-Thouless transition (2016)
  • Author(s): Morio Matsumoto, Daisuke Inotani, and Yoji Ohashi
  • Journal Title: Physical Review A Volume: 93 Issue: 1
  • DOI: 10.1103/physreva.93.013619
  • Peer Reviewed / Acknowledgement Compliant
• [Journal Article] Strong-coupling corrections to spin susceptibility in the BCS-BEC-crossover regime of a superfluid Fermi gas (2016)
  • Author(s): Hiroyuki Tajima, Ryo Hanai, and Yoji Ohashi
  • Journal Title: Physical Review A Volume: 93 Issue: 1
  • DOI: 10.1103/physreva.93.013610
  • Peer Reviewed / Acknowledgement Compliant
• [Journal Article] Proposed method to realize the p-wave superfluid state using an s-wave superfluid Fermi gas with a synthetic spin-orbit interaction (2015)
  • Author(s): Tokitake Yamaguchi and Yoji Ohashi
  • Journal Title: Ｐｈｙｓｉｃａｌ Review A Volume: 92 Issue: 1
  • DOI: 10.1103/physreva.92.013615
  • Peer Reviewed / Acknowledgement Compliant
• [Journal Article] Triplet pair amplitude in a trapped s-wave superfluid Fermi gas with broken spin rotation symmetry (2015)
  • Author(s): Yuki Endo, Daisuke Inotani, Ryo Hanai, and Yoji Ohashi
  • Journal Title: Ｐｈｙｓｉｃａｌ Review A Volume: 92 Issue: 2
  • DOI: 10.1103/physreva.92.023610
  • Peer Reviewed / Acknowledgement Compliant
• [Journal Article] Pairing fluctuations and an anisotropic pseudogap phenomenon in an ultracold superfluid Fermi gas with plural p-wave superfluid phases (2015)
  • Author(s): Daisuke Inotani and Yoji Ohashi
  • Journal Title: Physical Review A Volume: 92 Issue: 6
  • DOI: 10.1103/physreva.92.063638
  • Peer Reviewed / Acknowledgement Compliant
• [Presentation] Superfluid fluctuations and ground state properties of a strongly interacting Fermi atom gas, and applications to Neutron star physics (2017)
  • Author(s): Pieter van Wyk, Hiroyuki Tajima, Daisuke Inotani, Akira Ohnishi, and Yoji Ohashi
  • Organizer: 第5回ウィンタースクール・研究会「中性子星の核物質」
  • Place of Presentation: 福島飯坂温泉福住旅館(福島県・福島市)
• [Presentation] 基底状態にある超流動フェルミ原子気体に対する強結合補正 (2017)
  • Author(s): 田島裕之, Pieter van Wyk, 花井亮, 鏡原大地, 猪谷太輔, 堀越宗一, 大橋洋士
  • Organizer: 第5回ウィンタースクール・研究会「中性子星の核物質」
  • Place of Presentation: 福島飯坂温泉福住旅館(福島県・福島市)
• [Presentation] Hierarchical structure of matter states and a unified description on the viewpoint of BCS-BEC crossover physics (2017)
  • Author(s): 大橋洋士
  • Organizer: 研究会「クラスターがつなぐクォーク、ハドロン、原子核そして原子」
  • Place of Presentation: 大阪大学（大阪府・吹田市）
  • Invited
• [Presentation] Specific heat in an ultracold Bose-Fermi Mixture with a tunable pairing interaction (2017)
  • Author(s): Digvijay Kharga, Pieter van Wyk, Ryo Hanai, Daisuke Inotani, and Yoji Ohashi
  • Organizer: 日本物理学会
  • Place of Presentation: 大阪大学（大阪府・豊中市）
• [Presentation] BCS-BEC crossover physics in an ultracold Fermi gas with an Orbital Feshbach Resonance (2017)
  • Author(s): Soumita Mondal, Digvijay Kharga, Pieter van Wyk, Ryo Hanai, Daisuke Inotani, and Yoji Ohashi
  • Organizer: 日本物理学会
  • Place of Presentation: 大阪大学（大阪府・豊中市）
• [Presentation] p波超流動フェルミ原子気体における比熱に対する強結合効果 (2017)
  • Author(s): 猪谷太輔, Pieter van Wyk, 大橋洋士
  • Organizer: 日本物理学会
  • Place of Presentation: 大阪大学（大阪府・豊中市）
• [Presentation] ２次元フェルミ原子気体のBKT転移近傍における強結合効果と熱力学的性質 (2017)
  • Author(s): 松本杜青, 井亮, 猪谷太輔, 大橋洋士
  • Organizer: 日本物理学会
  • Place of Presentation: 大阪大学（大阪府・豊中市）
• [Presentation] Superfluid Instability and strong coupling effects in a Bose-Fermi mixture (2016)
  • Author(s): Digvijay Kharga, Pieter van Wyk, Ryo Hanai, Hiroyuki Tajima, Daisuke Inotani, and Yoji Ohashi
  • Organizer: 日本物理学会
  • Place of Presentation: 東北学院大学（宮城県・仙台市）
  • Year and Date: 2016-03-21
• [Presentation] p波相互作用するFermi原子気体における比熱に対する強結合効果 (2016)
  • Author(s): 猪谷太輔、Pieter van Wyk, 大橋洋士
  • Organizer: 日本物理学会
  • Place of Presentation: 東北学院大学（宮城県・仙台市）
  • Year and Date: 2016-03-21
• [Presentation] Strong coupling analysis of the equation of state of an ultracold Fermi gas in the BCS-BEC crossover region, and its application to neutron star physics II (2016)
  • Author(s): Pieter van Wyk, Hiroyuki Tajima, Daisuke Inotani, Akira. Ohnishi, and Yoji Ohashi
  • Organizer: 日本物理学会
  • Place of Presentation: 東北学院大学（宮城県・仙台市）
  • Year and Date: 2016-03-21
• [Presentation] Pairings in an ultracold Fermi gas and application to neutron star physics (2016)
  • Author(s): Yoji Ohashi
  • Organizer: Baymfest in Tokyo, Exploring extreme forms of matter
  • Place of Presentation: 東京大学（東京都・文京区）
  • Year and Date: 2016-03-14
  • Int'l Joint Research / Invited
• [Presentation] EOS of a Strongly Interacting Superfluid Fermi Gas Including an Effective Range, and Applications to Neutron Star Physics (2016)
  • Author(s): Pieter van Wyk, Hiriyuki Tajima, Daisuke Inotani, Akira Ohnishi, and Yoji Ohashi
  • Organizer: 新学術研究領域「実験と観測で解き明かす中性子星の核物質」研究会：低密度領域のEOS
  • Place of Presentation: 東京大学（東京都・文京区）
  • Year and Date: 2016-02-27
• [Presentation] ユニタリー領域近傍における超流動フェルミ原子気体の圧縮率の解析 (2016)
  • Author(s): 田島裕之、Pieter van Wyk, 花井亮、大橋洋士
  • Organizer: 新学術研究領域「実験と観測で解き明かす中性子星の核物質」研究会：低密度領域のEOS
  • Place of Presentation: 東京大学（東京都・文京区）
  • Year and Date: 2016-02-27
• [Presentation] Specific heat and phase diagram of a strongly interacting Fermi gas in the BCS-BEC crossover region (2016)
  • Author(s): Pieter van Wyk, Hiroyuki Tajima, Ryo Hanai, Yoji Ohashi
  • Organizer: Many-body Physics in Synthetic Quantum Systems
  • Place of Presentation: Stellenbosch (South Africa)
  • Int'l Joint Research
• [Presentation] Phase diagram of a strongly interacting Bose-Fermi mixture (2016)
  • Author(s): Digvijay Kharga, Daisuke Inotani, Ryo Hanai, Yoji Ohashi
  • Organizer: The 25th International Conference on Atom Physics (ICAP2016)
  • Place of Presentation: Seoul (Korea)
  • Int'l Joint Research
• [Presentation] Thermodynamic properties and effects of pairing fluctuations in a ultracold Fermi gas with a uniaxially anisotropic p-wave interaction (2016)
  • Author(s): Daisuke Inotani, Pieter van Wyk, Yoji Ohashi
  • Organizer: The 25th International Conference on Atom Physics (ICAP2016)
  • Place of Presentation: Seoul (Korea)
  • Int'l Joint Research
• [Presentation] Thermodynamic properties of a strongly interacting superfluid Fermi gas at zero temperature (2016)
  • Author(s): Hiroyuki Tajima, Pieter van Wyk, Ryo Hanai, Daichi Kagamihara, Daisuke Inotani, Munekazu Horikoshi, Yoji Ohashi
  • Organizer: The 25th International Conference on Atom Physics (ICAP2016)
  • Place of Presentation: Seoul (Korea)
  • Int'l Joint Research
• [Presentation] Pseudogapped density of states in a two-dimensional ultracold Fermi gas near the observed BKT transition temperature (2016)
  • Author(s): Morio Matsumoto, Ryo Hanai, Daisuke Inotani, Yoji Ohashi
  • Organizer: The 25th International Conference on Atom Physics (ICAP2016)
  • Place of Presentation: Seoul (Korea)
  • Int'l Joint Research
• [Presentation] Local Photoemission Spectrum in the BCS-BEC Crossover Regime of an Ultracold Fermi Gas in a Harmonic Trap (2016)
  • Author(s): Miki Ota, Hiroyuki Tajima, Ryo Hanai, Daisuke Inotani, and Yoji Ohashi
  • Organizer: The 25th International Conference on Atom Physics (ICAP2016)
  • Place of Presentation: Seoul (Korea)
  • Int'l Joint Research
• [Presentation] Equation of state of a Superfluid Fermi atom gas and Neutron star interior: Similarity and difference on the viewpoint of phase-shift corrections (2016)
  • Author(s): Pieter van Wyk, Hiroyuki Tajima, Daisuke Inotani, Akira Ohnishi, and Yoji Ohashi
  • Organizer: The 25th International Conference on Atom Physics (ICAP2016)
  • Place of Presentation: Seoul (Korea)
  • Int'l Joint Research
• [Presentation] Zero-temperature properties of a strongly-interacting superfluid Fermi gas in the BCS-BEC crossover region (2016)
  • Author(s): Hiroyuki Tajima, Pieter van Wyk, Ryo Hanai, Daichi Kagamihara, Daisuke Inotani, Munekazu Horikoshi, and Yoji Ohashi
  • Organizer: International Conference on Quantum Fluids and Solids (QFS2016)
  • Place of Presentation: Prague (Czech Republic)
  • Int'l Joint Research
• [Presentation] Single-particle properties of a strongly interacting Bose-Fermi mixture above the BEC phase transition temperature (2016)
  • Author(s): Digvijay Kharga, Dausike Inotani, Ryo Hanai, and Yoji Ohashi
  • Organizer: International Conference on Quantum Fluids and Solids (QFS2016)
  • Place of Presentation: Prague (Czech Republic)
  • Int'l Joint Research
• [Presentation] Strong coupling effects on specific heat of a Fermi gas with a p-wave interaction (2016)
  • Author(s): Daisuke Inotani, Pieter van Wyk, and Yoji Ohashi
  • Organizer: International Conference on Quantum Fluids and Solids (QFS2016)
  • Place of Presentation: Prague (Czech Republic)
  • Int'l Joint Research
• [Presentation] Pseudogap phenomena near the BKT transition of a two-dimensional ultracold Fermi gas in the crossover region (2016)
  • Author(s): Morio Matsumoto, Ryo Hanai, Daisuke Inotani, and Yoji Ohashi
  • Organizer: International Conference on Quantum Fluids and Solids (QFS2016)
  • Place of Presentation: Prague (Czech Republic)
• [Presentation] Superfluid Fermi atom gas in the crossover region and neutron star equation of state: Similarity and difference on the viewpoint of phase-shift corrections (2016)
  • Author(s): Pieter van Wyk, Hiroyuki Tajima, Daisuke Inotani, Akira Ohnishi, and Yoji Ohashi
  • Organizer: 理研シンポジウム・iTHES研究会 「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）
• [Presentation] 強く相互作用する２次元冷却フェルミ原子気体における擬ギャップ現象 (2016)
  • Author(s): 松本杜青, 花井亮, 猪谷太輔, 大橋洋士
  • Organizer: 理研シンポジウム・iTHES研究会 「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）
• [Presentation] 絶対零度近傍の超流動フェルミ原子気体の熱力学的性質と量子揺らぎ (2016)
  • Author(s): 田島裕之, Pieter van Wyk, 花井亮, 鏡原大地, 猪谷太輔, 堀越宗一, 大橋洋士
  • Organizer: 理研シンポジウム・iTHES研究会 「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）
• [Presentation] Ground state properties of a strongly interacting superfluid Fermi gas and application to neutron star EOS (2016)
  • Author(s): Yoji Ohashi, Pieter van Wyk, Hiroyuki Tajima, Munekazu Horikoshi, and Akira Ohnishi
  • Organizer: Workshop on Cold atoms
  • Place of Presentation: 理化学研究所（埼玉県・和光市）
  • Int'l Joint Research / Invited
• [Presentation] 強結合超流動フェルミ原子気体の絶対零度における圧縮率の定量的解析 (2016)
  • Author(s): 田島裕之, Pieter van Wyk, 花井亮, 鏡原大地, 猪谷太輔, 大橋洋士
  • Organizer: 日本物理学会
  • Place of Presentation: 金沢大学(石川県・金沢市）
• [Presentation] 一軸異方性を有するｐ波相互作用するフェルミ原子気体における熱力学的性質 (2016)
  • Author(s): 猪谷太輔, Pieter van Wyk, 大橋洋士
  • Organizer: 日本物理学会
  • Place of Presentation: 金沢大学(石川県・金沢市）
• [Presentation] ２次元フェルミ原子気体のBKT転移近傍における強結合効果とクーパー対形成 (2016)
  • Author(s): 松本杜青, 花井亮, 猪谷太輔, 大橋洋士
  • Organizer: 日本物理学会
  • Place of Presentation: 金沢大学(石川県・金沢市）
• [Presentation] Single particle spectral weight and strong coupling effects in a Bose-Fermi mixture (2016)
  • Author(s): Digvijay Kharga, Daisuke Inotani, Ryo Hanai, Pieter van Wyk, Hiroyuki Tajima, and Yoji Ohashi
  • Organizer: 日本物理学会
  • Place of Presentation: 金沢大学(石川県・金沢市）
• [Presentation] Superfluid Fermi atom gas in the crossover region and Neutron star interior: Similarity and difference on the viewpoint of phase-shift corrections to equation of state (2016)
  • Author(s): Pieter van Wyk, Hiroyuki Tajima, Daisuke Inotani, Akira Ohnishi, and Yoji Ohashi
  • Organizer: 日本物理学会
  • Place of Presentation: 金沢大学(石川県・金沢市）
• [Presentation] Strong-coupling properties of a superfuid Fermi gas and application to neutron-star equation of state (2016)
  • Author(s): Yoji Ohashi
  • Organizer: International Symposium on Neutron Star Matter (NSMAT2016)
  • Place of Presentation: 東北大学（宮城県・仙台市）
  • Int'l Joint Research / Invited
• [Presentation] Many-body quantum corrections to ground state properties of a superfluid Fermi gas and application to neutron star physics (2016)
  • Author(s): 大橋洋士
  • Organizer: グローバル創造クラスター「量子コミュニティ」シンポジウム
  • Place of Presentation: 慶應義塾大学（神奈川県横浜市）
• [Presentation] BCS-BEC crossover phenomena in an ultracold Fermi gas and application to neutron star physics (2015)
  • Author(s): 大橋洋士
  • Organizer: 「高密度核物質と中性子星」研究会
  • Place of Presentation: 京都大学（京都府・京都市）
  • Year and Date: 2015-12-20
  • Invited
• [Presentation] EOS of an ultracold Fermi gas in the BCS-BEC crossover region and application to neutron stars (2015)
  • Author(s): 大橋洋士, Pieter van Wyk, 大西明
  • Organizer: 新学術研究領域「実験と観測で解き明かす中性子星の核物質」第4回研究会
  • Place of Presentation: 湘南国際村センター（神奈川県・三浦郡）
  • Year and Date: 2015-09-18
• [Presentation] Strong coupling analysis of the equation of state of an ultracold Fermi gas in the BCS-BEC crossover region, and its application to neutron star physics (2015)
  • Author(s): Pieter van Wyk, Hiroyuki Tajima, Daisuke Inotani, Akira. Ohnishi, and Yoji Ohashi
  • Organizer: 日本物理学会
  • Place of Presentation: 関西大学（大阪府・吹田市）
  • Year and Date: 2015-09-17
• [Presentation] 調和ポテンシャル中の冷却フェルミ原子気体の局所スピン帯磁率における非一様な強結合効果 (2015)
  • Author(s): 田島裕之、大橋洋士
  • Organizer: 「熱場の量子論」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: 2015-08-31
• [Presentation] Spin susceptibility and effects of inhomogeneous strong pairing fluctuations in a trapped ultracold Fermi gas (2015)
  • Author(s): Hiroyuki Tajima, Ryo Hanai, and Yoji Ohashi
  • Organizer: International symposium on Quantum Fluids and Solids (QFS2015)
  • Place of Presentation: New York (USA)
  • Year and Date: 2015-08-13
  • Int'l Joint Research
• [Presentation] Strong Coupling Effects on the Specific Heat of an Ultracold Fermi Gas in the Unitarity Limit (2015)
  • Author(s): Pieter van Wyk, Hiroyuki Tajima, Ryo Hanai, and Yoji Ohashi
  • Organizer: International symposium on Quantum Fluids and Solids (QFS2015)
  • Place of Presentation: New York (USA)
  • Year and Date: 2015-08-13
  • Int'l Joint Research
• [Remarks] 慶應義塾大学研究者情報総覧（理工学部物理学科 大橋洋士）
  • URL: http://k-ris.keio.ac.jp/Profiles/123/0012288/profile.html