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

• Project/Area Number: 17J01238
• Research Category: Grant-in-Aid for JSPS Fellows
• Allocation Type: Single-year Grants
• Section: 国内
• Research Field: Condensed matter physics I
• Research Institution: Osaka University
• Principal Investigator: 花井 亮 大阪大学, 理学研究科, 特別研究員(PD)
• Project Period (FY): 2017-04-26 – 2020-03-31
• Project Status: Completed (Fiscal Year 2019)
• Budget Amount: ¥4,420,000 (Direct Cost: ¥3,400,000、Indirect Cost: ¥1,020,000); Fiscal Year 2019: ¥1,430,000 (Direct Cost: ¥1,100,000、Indirect Cost: ¥330,000); Fiscal Year 2018: ¥1,430,000 (Direct Cost: ¥1,100,000、Indirect Cost: ¥330,000); Fiscal Year 2017: ¥1,560,000 (Direct Cost: ¥1,200,000、Indirect Cost: ¥360,000)
• Keywords: 非エルミート量子多体理論 / 臨界現象 / 励起子ポラリトン / 非平衡相転移 / 非エルミート量子力学 / ボース・アインシュタイン凝縮 / 半導体レーザー / 励起子 / 非平衡定常状態 / 量子多体効果

Outline of Annual Research Achievements

本年度は、非平衡開放多体量子系の研究を行い、流入と流出のある非平衡二成分凝縮体（例：励起子ポラリトン凝縮体、プラズモニック格子凝縮体、二重井戸ポテンシャル中の流入・流出のあるボーズ凝縮体）において、通常の臨界現象とは本質的に異なる、新しい機構による動的臨界現象が現れることを明らかにした。

通常、臨界現象は、自由エネルギーが臨界点近くで平らになり、振幅モードがソフト化することによって生じる。このとき、振幅モードとゴールドストーンモードは常に直交している。しかし、我々の研究対象である流入と流出のある多体系では、系の集団的運動が非エルミート的となるため、これらが非直交となることが許される。我々は、その結果、振幅モードがゴールドストーンモードと「合流」した点である「臨界例外点」が現れることを明らかにした。臨界例外点では、生じうる集団モードがゴールドストーンモードに限定されているいるため、すべての熱的ノイズ・非平衡ノイズにより生じた揺らぎがゴールドストーンモードへと変換される。これが、空間4次元以下で発散する、異常に大きな揺らぎが発達した、特異な臨界現象をもたらすことを示した。さらに臨界例外点近傍において動的繰り込み群解析を行った結果、空間8次元近傍においてHohenberg and Halperinによる分類にはない、新たなユニバーサリティークラスに属するWilson-Fisher fixed pointが現れることを示し、強相関効果が異常に大きな揺らぎにより異常に発達していることを示すことに成功した。
以上の成果に加え、Pittsburgh大学のSnokeグループおよびNRELのMascarenhasグループと共同で、ポラリトン凝縮体の量子揺らぎによるHiggsモードの観測に成功した他、冷却原子系において、非平衡性による強相関効果の増大する方法を提案した。

Research Progress Status

令和元年度が最終年度であるため、記入しない。

Strategy for Future Research Activity

令和元年度が最終年度であるため、記入しない。

Research Products

• [Journal Article] Nonequilibrium strong-coupling theory for a driven-dissipative ultracold Fermi gas in the BCS-BEC crossover region (2020)
  • Author(s): Kawamura Taira、Hanai Ryo、Kagamihara Daichi、Inotani Daisuke、Ohashi Yoji
  • Journal Title: Physical Review A Volume: 101 Issue: 1 Pages: 013602-013602
  • DOI: 10.1103/physreva.101.013602
  • Peer Reviewed
• [Journal Article] Non-Hermitian Phase Transition from a Polariton Bose-Einstein Condensate to a Photon Laser (2019)
  • Author(s): Hanai Ryo、Edelman Alexander、Ohashi Yoji、Littlewood Peter B.
  • Journal Title: Physical Review Letters Volume: 122 Issue: 18 Pages: 185301-185301
  • DOI: 10.1103/physrevlett.122.185301
  • Peer Reviewed / Int'l Joint Research
• [Journal Article] Strong-Coupling Theory for a Non-equilibrium Unitary Fermi Gas (2019)
  • Author(s): Kawamura T.、Kagamihara D.、Hanai R.、Ohashi Y.
  • Journal Title: Journal of Low Temperature Physics Volume: - Issue: 1-2 Pages: 41-48
  • DOI: 10.1007/s10909-019-02310-7
  • Peer Reviewed
• [Journal Article] Photoluminescence and gain/absorption spectra of a driven-dissipative electron-hole-photon condensate (2018)
  • Author(s): Hanai Ryo、Littlewood Peter B.、Ohashi Yoji
  • Journal Title: Physical Review B Volume: 97 Issue: 24 Pages: 245302-245302
  • DOI: 10.1103/physrevb.97.245302
  • Peer Reviewed / Int'l Joint Research
• [Journal Article] Pairing fluctuations in a strongly interacting two-dimensional Fermi gas (2018)
  • Author(s): Matsumoto Morio、Hanai Ryo、Inotani Daisuke、Ohashi Yoji
  • Journal Title: Journal of Physics: Conference Series Volume: 969 Pages: 012012-012012
  • DOI: 10.1088/1742-6596/969/1/012012
  • Peer Reviewed / Open Access
• [Journal Article] Pseudogap Regime of a Two-dimensional Uniform Fermi Gas (2018)
  • Author(s): Morio Matsumoto、Ryo Hanai、Daisuke Inotani、Yoji Ohashi
  • Journal Title: Journal of the Physical Society of Japan Volume: 87 Issue: 1 Pages: 014301-014301
  • DOI: 10.7566/jpsj.87.014301
  • NAID: 210000134666
  • Peer Reviewed
• [Journal Article] Strong-coupling corrections to ground-state properties of a superfluid Fermi gas (2017)
  • Author(s): Hiroyuki Tajima, Pieter van Wyk, Ryo Hanai, Daichi Kagamihara, Daisuke Inotani, Munekazu Horikoshi, and Yoji Ohashi
  • Journal Title: Physical Review A Volume: 95 Issue: 4 Pages: 043625-043625
  • DOI: 10.1103/physreva.95.043625
  • Peer Reviewed / Acknowledgement Compliant
• [Journal Article] Spin susceptibility and effects of a harmonic trap in the BCS-BEC crossover regime of an ultracold Fermi gas (2017)
  • Author(s): Hiroyuki Tajima, Ryo Hanai, and Yoji Ohashi
  • Journal Title: Physical Review A Volume: 96 Issue: 3 Pages: 033614-033614
  • DOI: 10.1103/physreva.96.033614
  • Peer Reviewed
• [Journal Article] Single-Particle Excitations and Effects of Hetero-Pairing Fluctuations in a Bose-Fermi Mixture with a Feshbach Resonance (2017)
  • Author(s): Digvijay Kharga, Daisuke Inotani, Ryo Hanai, and Yoji Ohashi
  • Journal Title: Journal of the Physical Society of Japan Volume: 86 Issue: 8 Pages: 084301-084301
  • DOI: 10.7566/jpsj.86.084301
  • Peer Reviewed
• [Journal Article] Local Photoemission spectra and effects of spatial inhomogeneity in the BCS-BEC crossover regime of a trapped ultracold Fermi gas (2017)
  • Author(s): M. Ota, H. Tajima, R. Hanai, D. Inotani, Y. Ohashi
  • Journal Title: Physical Review A Volume: 95 Pages: 053623-053623
  • Peer Reviewed
• [Journal Article] Dynamical instability of a driven-dissipative electron-hole condensate in the BCS-BEC crossover region (2017)
  • Author(s): Ryo Hanai, Peter B. Littlewood, and Yoji Ohashi
  • Journal Title: Physical Review B Volume: 96 Issue: 12 Pages: 125206-125206
  • DOI: 10.1103/physrevb.96.125206
  • Peer Reviewed / Int'l Joint Research
• [Presentation] Critical exceptional point in a driven-dissipative coupled condensate (2020)
  • Author(s): Ryo Hanai, Alexander Edelman, Yoji Ohashi, and Peter B. Littlewood
  • Organizer: 10th International Conference on Spontaneous Coherence in Excitonic systems (ICSCE10)
  • Int'l Joint Research
• [Presentation] Non-Hermitian phase transition and the rise of a critical exceptional point in driven-dissipative condensates (2019)
  • Author(s): Ryo Hanai
  • Organizer: Yale Quantum Institute Talk (YQI Talk)
  • Int'l Joint Research / Invited
• [Presentation] Non-Hermitian phase transition from polariton BEC to photon laser and the critical exceptional point (2019)
  • Author(s): Ryo Hanai, Alexander Edelman, Yoji Ohashi, and Peter B. Littlewood
  • Organizer: MURI: Polaritronics, Second-Annual Review
  • Int'l Joint Research
• [Presentation] 非エルミート凝縮体に現れる臨界例外点 (2019)
  • Author(s): 花井亮、Peter B. Littlewood
  • Organizer: 日本物理学会秋季大会
• [Presentation] Phase transition/crossover from a polariton Bose-Einstein condensate to a photon laser (2018)
  • Author(s): Ryo Hanai, Alexander Edelman, Yoji Ohashi, Peter B. Littlewood
  • Organizer: Correlation and entanglement with photons in cavities (CEPC2018)
  • Int'l Joint Research
• [Presentation] POLARITON TO PHOTON LASER TRANSITION AND THE EMERGENCE OF A NONEQUILIBRIUM CRITICAL POINT (2018)
  • Author(s): Ryo Hanai, Alexander Edelman, Yoji Ohashi, Peter B. Littlewood
  • Organizer: The 9th International Conference on Spontaneous Coherence in Excitonic Systems (ICSCE-9)
  • Int'l Joint Research
• [Presentation] A nonequilibrium phase transition and critical phenomena in a polariton condensate (2018)
  • Author(s): Ryo Hanai, Alexander Edelman, Yoji Ohashi, Peter B. Littlewood
  • Organizer: Correlated electron systems --- novel developments
  • Int'l Joint Research
• [Presentation] 励起子ポラリトン系における第二閾値の出現およびPT対称な例外点周りのクロスオーバー現象 (2018)
  • Author(s): 花井亮, Alexander Edelman, 大橋洋士, Peter B. Littlewood
  • Organizer: 日本物理学会秋季大会
• [Presentation] Optical properties of highly-excited exciton-polariton condensate (2018)
  • Author(s): R. Hanai, P. B. Littlewood, Y. Ohashi
  • Organizer: APS March Meeting 2018
  • Int'l Joint Research
• [Presentation] Photoluminescence of a highly excited exciton-polariton condensate with pumping and decay (2017)
  • Author(s): R. Hanai, P. B. Littlewood, Y. Ohashi
  • Organizer: The 18th International Conference on Physics of Light-Matter Coupling in Nanostructures (PLMCN18)
  • Int'l Joint Research
• [Presentation] PHOTOLUMINESCENCE OF A DRIVEN-DISSIPATIVE EXCITON-POLARITON CONDENSATE IN THE HIGHLY-EXCITED REGIME (2017)
  • Author(s): R. Hanai, P. B. Littlewood, Y. Ohashi
  • Organizer: International School and Workshop on Electronic Crystals (ECRYS-2017)
  • Int'l Joint Research
• [Presentation] 電子正孔気体における非平衡強結合効果 (2017)
  • Author(s): 花井亮
  • Organizer: 日本物理学会秋季大会