東京科学大学 理学院 物理学系
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The interior of a neutron star is expected to be occupied by neutron superfluids. While the outer region should be filled by 1S0 superfluids consisting of a conventional singlet pairs of neutrons, the inner core may be 3P2 superfluids consisting of a condensate of spin-triplet p-wave Cooper pairs of neutrons with total angular momentum J=2 . This has rich topological structures in both momentum and real spaces: it is a topological superfluid and admits various topological defects such as half-quantum non-Abelian vortices, domain walls, surface topological defects, boojums, and so on. I will give a review of the current status of 3P2 superfluids with a particular attention to vortices and possible applications to pulsar glitches.

※Zoom情報：https://zoom.us/meeting/register/6aN7eizNRL–W58_kNle8A

連絡教員：物理学系　関澤　一之（内線2463）

https://www.phys.sci.isct.ac.jp/wp/wp-content/uploads/2025/12/432.pdf

https://cmsp.phys.s.u-tokyo.ac.jp/

理学院 物理学系の花井亮准教授が、第20回（2025年度）凝縮系科学賞を受賞しました。表彰式は11月27日に行われました。

The superradiant phase transition (SRPT) is a second-order phase transition where a static electric or magnetic field is ordered spontaneously due to an ultrastrong interaction with matters in thermal equilibrium. Although the SRPT has not been observed since its first prediction in 1973, its magnonic (spin-wave) version was confirmed in a magnetic material ErFeO3 recent years [1-3]. In this seminar, we will present experimental results [1,3] and theoretical background [2] of this magnonic SRPT. In addition, thermal-equilibrium quantum squeezing obtained at the SRPT critical point [4] will also be presented. The quantum technologies like quantum computing have been developed basically based on non-equilibrium phenomena. Because quantum states in those phenomena are usually excited states in systems of interest, such states are easily destroyed due to a variety of decoherence phenomena. In contrast, the SRPT provides quantum squeezing in the most stable state of systems in thermal equilibrium, thus its squeezing is robust against decoherence, which might give us a foundation of decoherence-robust quantum technologies.

[1] X. Li, M. Bamba, N. Yuan, Q. Zhang, Y. Zhao, M. Xiang, K. Xu, Z. Jin, W. Ren, G. Ma, S. Cao, D. Turchinovich, and J. Kono, Observation of Dicke cooperativity in magnetic interactions. Science 361, 794–797 (2018).
[2] M. Bamba, X. Li, N. Marquez Peraca, and J. Kono, Magnonic superradiant phase transition. Communications Physics 5, 3 (2022).
[3] D. Kim, S. Dasgupta, X. Ma, J.-M. Park, H.-T. Wei, X. Li, L. Luo, J. Doumani, W. Yang, D. Cheng, R. H. J. Kim, H. O. Everitt, S. Kimura, H. Nojiri, J. Wang, S. Cao, M. Bamba, K. R. A. Hazzard, and J. Kono, Observation of the magnonic Dicke superradiant phase transition. Sci. Adv. 11, eadt1691 (2025).
[4] K. Hayashida, T. Makihara, N. Marquez Peraca, D. Fallas Padilla, H. Pu, J. Kono, and M. Bamba, Perfect intrinsic squeezing at the superradiant phase transition critical point. Sci. Rep. 13, 2526 (2023).

連絡教員：藤井　啓資（内線2136）

https://www.phys.sci.isct.ac.jp/wp/wp-content/uploads/2025/12/431.pdf

マヨラナ準粒子を始めとする非自明なエッジ状態を有するトポロジカル超伝導は様々な非従来型超伝導体において実現されることが明らかになってきた。このエッジ状態の起源は、ハミルトニアンの有するトポロジカル不変量に帰することが知られている[1-2]。
講演では、トポロジカル超伝導の持つ顕著な性質である1)常伝導金属との接合における零電圧コンダクタンスピーク[3]、2)ジョセフソン電流[3]、3)常伝導金属中の準粒子状態密度がゼロエネルギーでピークを持つ奇周波数電子対による異常近接効果[2,4-5]を紹介する。

[1] Y. Tanaka, M. Sato, N. Nagaosa, J. Phys. Soc. Jpn. 81, 011013, 2012.
[2] 超伝導接合の物理　田仲由喜夫著　名古屋大学出版会　2021年
[3] Y. Tanaka and S. Kashiwaya, Phys. Rev. Lett., 74, 3451, 1995; Phys. Rev. B 56, 892, 1997.
[4] Y. Tanaka and S. Kashiwaya, Phys. Rev. B, 70, 012507, 2004.
[5] Y. Tanaka S. Tamura and J. Cayao, Prog. Theor. Exp. Phys., 08C105 2024.

※「物理学特別講義（発展）第九」を履修する学生は本セミナーも聴講すること。

連絡教員　　打田　正輝（内線2756）

https://www.phys.sci.isct.ac.jp/wp/wp-content/uploads/2025/12/430-henkou.pdf

Our lab uses quantitative microscopy and theory to develop constitutive and closure relations that bridge the particle-to-continuum field scales. In this seminar, I describe our application of feedback control on self-propelled agents to create spatiotemporal patterns and user-specified population distributions. We demonstrate the use of “gray-box models” that incorporate partially-known dynamics and learn the difficult-to-model terms (e.g., many-body interactions). We use the concepts of observability and time-delay embedding to model, forecast, and control the complex behaviors of active matter using continuum density data alone. By forcing the system to sample rare configurations, we can develop new constitutive field relations with appropriate closures. This project is aimed at deepening our understanding of mode coupling in nonlinear dynamics across the length and time scales.

連絡教員：物理学系　西口　大貴（内線2447）

https://www.phys.sci.isct.ac.jp/wp/wp-content/uploads/2025/12/117tokubetsu.pdf