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セミナー
2026.09.01
講師：浅野 元紀 氏（NTT物性科学基礎研究所）
日時：令和8年9月29日（火）14:00-15:30
場所：本館3階 345 理学院第2会議室振り子や弦から、固体、分子、流体に至るまで、物体の振動は物質やスケールを問わず自然界に遍在する普遍的な自由度である。一見単純な調和振動子として記述される一方、現実には揺らぎや散逸を伴う開放系であり、その非線形性は同期やカオスなど多彩なダイナミクスを生み出す。さらに近年では、巨視的な振動の量子的性質も研究対象となっている。それでは、あらゆる振動体を、その量子性が顕在化する極限まで計測・制御できるのだろうか――その極限に迫るほどに顕在化する微小な揺らぎや散逸、非線形性、さらには他の自由度との相互作用こそが、従来の調和振動子像を超えた新たな物理を切り拓く鍵になると期待される。
この問いに迫る実験基盤として、我々は共振器オプトメカニクスに着目している。これまで、光ファイバ上の微小光共振器を基盤に、古典流体中での微小振動計測[1]、多数の振動子からなるオプトメカニカルアレイ[2]、光による振動子間相互作用と非線形ダイナミクスの制御[3]へと研究を展開してきた。本講演ではこれらを概説するとともに、揺らぎと散逸のもとで創発する非線形・非平衡現象、さらにマグノメカニクスや超流動体など新たな振動自由度への展開について紹介する。
[1] M. Asano et al., Sci. Adv. 8, eabq2502 (2022).
[2] M. Asano et al., Phys. Rev. Appl. 21, 024013 (2024).
[3] M. Asano et al., Sci. Adv. 11, eady4167 (2025).連絡教員：物理学系 賀川 史敬（内線2561）
https://www.phys.sci.isct.ac.jp/wp/wp-content/uploads/2026/09/449.pdf
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セミナー
2026.08.28
講師：Professor Kenneth R. Poeppelmeier（Northwestern University, USA）
日時：令和8年9月15日（火）15:30-17:00
場所：南5号館1階 103B 第2会議室
Racemates have been assumed to be optically inactive for the last 170 years. The cancelation of opposite rotations from left- and right-handed enantiomers (racemates) was discussed by Pasteur for tartaric acids and has never been dismissed. However, Pasteur opened a question: “En est-il toujours ainsi? C’est à l’expérience de répondre”, which could be translated as “Is it always true? The experiments should tell us”.
Specific arrangements of racemic units, however, can lead to optical activity, and as many as one in twenty racemic compounds are potential optically active materials. These form an important and often overlooked class of noncentrosymmetric structures with broken inversion symmetry. This talk is based in part on a paper that we published several years ago with the title “Machine-learning-assisted Synthesis of Polar Racemates,” that describes our efforts to synthesize other new members of a peculiar class of noncentrosymmetric (NCS) materials (crystal class mm2, space group Pna21) first reported in “From Racemic Units to Polar Materials,” R. Gautier et al., Cryst. Growth Des., 12, 6267–6271 (2012).
Crystalline solids in general are governed by universal structure-property relationships derived from their crystal symmetry, leading to paradigmatic rules on what properties they can and cannot exhibit. Another long-held structure-property relationship is that centrosymmetric crystals cannot differentially absorb circularly polarized light.
In our recent paper, “Differential Absorption of Circularly Polarized Light by a Centrosymmetric Inorganic Crystal,” K. A. Parrish et al., Science, doi: 10.1126/science. Adr 5478 (2025); Erratum: doi: 10.1126/science. Aec 1372, we demonstrate the design, synthesis and characterization of the centrosymmetric material Li2Co3(SeO3)4, which violates this relationship, not by defying symmetry-imposed selection rules, but by invoking a photophysical process not previously characterized for crystalline solids. This process originates from an interference between linear dichroism and linear birefringence, referred to as LD-LB, enabling a chiroptical response under centrosymmetry, and involves strong chiroptical signals that invert upon sample flipping.連絡教員：物理学系 佐藤 琢哉（内線2716）
https://www.phys.sci.isct.ac.jp/wp/wp-content/uploads/2026/08/122tokubetsu.pdf
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セミナー
2026.08.24
講師：松下 太樹 氏（大阪大学 大学院基礎工学研究科）
日時：令和8年9月18日（金）10:00-
場所：本館2階 290 物理学系輪講室凝縮身体の集団冷気は、秩序パラメータの振幅、移送、及び内部自由度の揺らぎとして現れ、日従来型超伝導体における対称性の破れを反映する。そのため、集団励起に由来する応答現象を明らかにすることは、超伝導秩序の対称性と内部構造を同定するうえで重要である。
本発表では、まず、多バンド超伝導体におけるLeggettモードの光学応答 [1,2] や、ネマティック超伝導体におけるNematicityモードおよびカイラルHiggsモードの電磁応答 [3] を例として、超伝導集団励起と分光応答の関係を概観する。続いて、カイラル超伝導に固有の集団励起であるClappingモードに焦点を当て、その光学・音響応答に関する我々の研究成果を報告する。
Clappingモードは、カイラル超伝導体におけるCooper対の角運動量の揺らぎに起因する集団励起である。我々は、正常状態における弱い粒子正孔非対称性を考慮すると、音波がClappingモードと結合し、音響波の伝播方向に垂直な交流電流を誘起する異常音響電気効果が引き起こされることを示した [4]。この異常音響電気効果は、音速とFermi速度が同程度の重い電子系において、Clappingモードとの共鳴によって増強されるため、その検出手段を提供する。さらに、多バンドカイラル超伝導体では、Clappingモードがマイクロ波領域の磁気光学応答を支配し、Kerr回転およびFaraday回転に特徴的な共鳴構造を生じることを議論する [5]。本発表では、これらの結果を通じて、磁気光学応答と異常音響電気効果を観測することで、カイラル超伝導秩序における対称性の破れと集団励起を同時に検出できることを示す。
[1] T. Kamatani, S. Kitamura, N. Tsuji, R. Shimano, and T. Morimoto, Phys. Rev. B 105, 094520 (2022).
[2] R. Nagashima, S. Tian, R. Haenel, N. Tsuji, and D. Manske, Phys. Rev. Research 6, 013120 (2024).
[3] H. Uematsu, T. Mizushima, A. Tsuruta, S. Fujimoto, and J. A. Sauls, Phys. Rev. Lett. 123, 237001 (2019).
[4] T. Matsushita, T. Mizushima, I. Vekhter, and S. Fujimoto, Phys. Rev. B 105, 134520 (2022).
[5] T. Matsushita, J. Ieda, Y. Araki, T. Morimoto, I. Vekhter, and Y. Yanase, arXiv:2601.10151 (2026).連絡教員：物理学系 石塚 大晃（内線2488）
https://www.phys.sci.isct.ac.jp/wp/wp-content/uploads/2026/08/448.pdf
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セミナー
2026.07.10
講師：Dr. Oh Changgeun （東京大学 大学院工学系研究科 物理工学専攻）
日時：令和8年7月27日（月）15:30-
場所：本館2階 227C 物理学系輪講室Quantum geometry, which describes the geometric structure of Bloch wave functions in momentum space, has emerged as a key research topic in condensed matter physics. While the Berry curvature has been extensively studied for its role in determining topological properties, the influence of the quantum metric or quantum distance on material properties has only recently gained significant attention. This presentation explores the impact of quantum geometry on various material properties, focusing on the following aspects:
1. Mass-Invariant universal optical conductivity: In isotropic quadratic band touching semimetals, the optical conductivity is universally given by a geometric quantity independent of the detailed band structure.
2. Bulk-interface correspondence in singular flat band systems: Bulk-edge correspondence is a fundamental concept in topological physics. While previous studies have focused on the topological properties of wave functions in relation to boundary modes, we demonstrate that another geometric quantity—the quantum distance—can also establish a bulk-interface correspondence in singular flat band systems.
3. Third harmonic generation of Higgs mode in superconductor: Collective modes in superconductors, such as the Higgs mode, offer deep insights into the nature of condensates. Third-harmonic generation is a primary tool for probing the Higgs mode, but its signal competes with that of quasiparticle excitations depending on impurity scattering rates.
In particular, in the clean regime the standard BCS theory generally predicts the dominance of quasiparticle contributions. Here, we propose and demonstrate that the quantum geometry of electronic bands can be a key mechanism governing this competition.連絡教員：物理学系 藤井 啓資（内線2136）
https://www.phys.sci.isct.ac.jp/wp/wp-content/uploads/2026/07/447.pdf
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セミナー
2026.06.29
講師：Dr. Flavio Ronetti（Aix Marseille University, France）
日時：令和8年7月7日（火）13:30-
場所：本館1階 M112 講義室Anyons, quasiparticles with exchange statistics intermediate between bosons and fermions, are among the most distinctive excitations of fractional quantum Hall systems. Their fractional charge has long been accessed through shot-noise measurements at quantum point contacts, but a direct and robust detection of their braiding statistics remains a central challenge. In this seminar, I will discuss several transport-based approaches to probing anyonic properties in fractional quantum Hall edge states.
First, I will show how the finite spatial width of anyons can strongly affect braiding-induced transport signatures, even when this width is extremely small. This effect is especially relevant for hierarchical states and provides a possible explanation for recent experiments at filling factor (ν=2/5). I will then discuss
photo-assisted shot noise as a tool to identify multiple tunneling charges in states with several edge modes, focusing on the case (ν=2/3), where different quasiparticle charges may tunnel simultaneously at a quantum point contact.
Finally, I will present proposals for directly measuring the anyonic statistical angle using controlled time-dependent transport. These setups rely on anyons emitted from a QPC source and braided either around a fractional quantum Hall droplet or through a closed-loop geometry on a single chiral edge. In these schemes, the time-dependent current and current cross-correlations carry signatures governed by the statistical phase, while suitable protocols allow the extraction of the anyonic angle without requiring independent knowledge of non-universal parameters. Together, these results highlight how edge transport can provide experimentally accessible and theoretically sharp probes of fractional charge, braiding, and anyonic statistics.
The following published papers are related to this work:
https://arxiv.org/abs/2311.15094
https://arxiv.org/abs/2502.15909
https://arxiv.org/abs/2503.17008
https://arxiv.org/abs/2506.09774連絡教員：物理学系 藤澤 利正（内線2750）
https://www.phys.sci.isct.ac.jp/wp/wp-content/uploads/2026/06/446.pdf
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セミナー
2026.06.24
講師：Professor Sven van Teeffelen（The University of Montreal, Montreal, CANADA ）
日時：令和8年7月1日（水）13:30-
場所：南5号館5階 503CD 大会議室 および Zoom*All living cells are bounded by envelopes that protect them from the environment and confer their sizes and shapes. These shapes help cells to spatially organize their internal biological processes, allowing them to divide and faithfully segregate genetic material to each daughter. Yet, we still know very little about how cells obtain and control cell shape, even in the arguably simplest and best understood organism: the rod-shaped Escherichia coli.
To resist a high intracellular osmotic pressure, bacteria and many other single-celled organisms are surrounded by a cell wall, an elastic, covalent meshwork of sugars and peptides. For walled cells to grow, they must enzymatically cut cell-wall bonds while inserting new cell-wall material to prevent envelope rupture. How do cells control a straight rod-like cell geometry with a well-defined diameter, while also maintaining cell-wall integrity and increasing cell length at a rate that accommodates biomass growth? We have made important progress in the past two decades.
Here, I will present two related vignettes that answer aspects of these questions in Gram-negative rod-shaped bacteria: First, I will present experiments showing that cells couple the global rate of envelope growth to metabolism, i.e., they increase their envelope in proportion to the production of biomass, likely at the level of the outer membrane. Second, I will present how mechanical forces and envelope curvature contribute to the regulation of cell shape locally, through cytoskeletal proteins and autolytic enzymes, based on coarse-grained computer simulations.※本セミナーは学術変革領域(A)「動的物質科学の創成 量子と古典の枠を超える」との共催です。
＊本 ZOOM セミナーに参加されます場合には、事前に下記より登録を済ませてください。https://zoom.us/meeting/register/_HDG8eelQfa4fMUVRtLP3A
当日会場にお越しいただけます方は、登録不要ですので、是非、対面でご参加ください。
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/2026/06/445.pdf
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セミナー
2026.06.02
【開催日変更】
講師：Dr. Ho Hsiao（Center for Computational Sciences, University of Tsukuba）
日時：令和8年6月24日（水）16:00-
場所：本館2階 290 物理学系輪講室In the context of Composite Higgs Models, where the standard model Higgs is interpreted as a pseudo Nambu-Goldstone Boson emerging from a new strong sector, baryons formed by matters in different representations, known as chimera baryons, could serve as top partners. The chimera baryon sharing the same quantum number as the top quark can mix with it, effectively lifting the mass of the top quark. We report our results of the spectrum of low-lying chimera baryons in the quenched approximation on a Sp(4) gauge theory. We perform spin and parity projections to separate the states and study their mass hierarchy. Particularly, we investigate the chiral extrapolation of chimera baryon masses. To accomplish this, we use a fitting function inspired by QCD chiral Effective Field Theory (EFT). Lastly, we present our current results using the dynamical fermions. 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/2026/06/120tokubetsu-henkou.pdf
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セミナー
2026.05.28
講師：Dr. Alexis Poncet（CNRS, Laboratoire de physique à l'ENS de Lyon, Lyon, France ）
日時：令和8年6月8日（月）10:30-
場所：南5号館5階 503CD 大会議室 および Zoom*In systems far from thermal equilibrium, structure and dynamics are intertwined, leading to emergent phenomena such as collective motion in active matter or anomalous wave propagation in nonreciprocal systems. This talk explores the role of microscopic interactions in shaping these behaviors: What forms do they take? What are their consequences at macroscopic scales? And how can we infer them from experiments?
In the first part, I will present a study of self-propelled Janus particles (developed in the Nishiguchi lab), which exhibit coherent flocking at the collective level. Using a recent framework known as Stochastic Force Inference, we learned the microscopic interactions between particles [1]. These interactions not only reproduce experimental observables in simulations but also reveal a mechanism for flocking: pairwise torques that cause particles to turn away from their neighbors.
The second part focuses on flowing droplets with nonreciprocal hydrodynamic interactions, where left/right asymmetry gives rise to unexpected dynamics. Despite being overdamped, a 1D stream of such droplets supports nonlinear waves due to nonreciprocal coupling. Theoretically, we predict solitary waves described by the Korteweg–de Vries (KdV) equation (or KdV-Burgers with damping) [2]. A physics-informed neural network further uncovers this dynamics directly from experimental data.
If time permits, I will briefly discuss two ongoing theoretical projects on active and nonreciprocal systems: (1) how memory effects in viscoelastic media alter Motility-Induced Phase Separation of active particles, and (2) how Kardar-Parisi-Zhang fluctuations are evidenced in a 1D lattice model with nonreciprocal interactions.
[1] Hem, Poncet, Ronceray, Nishiguchi & Démery, Soft Matter 21 (37), 7257-7269 (2025)
[2] Colen, Poncet, Bartolo & Vitelli, Physical Review Letters 133 (10), 107301 (2024)
※本セミナーは学術変革領域(A)「動的物質科学の創成 量子と古典の枠を超える」との共催です。
＊Zoom 登録リンク：https://zoom.us/meeting/register/qw3pWA-kTjW7F01RXWqJSg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/2026/05/121tokubetsu.pdf
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セミナー
2026.05.22
講師：鈴木 史花 氏（東京大学 素粒子物理国際研究センター）
日時：令和8年6月10日（水）13:30-
場所：本館2階 290 物理学系輪講室The Kibble–Zurek mechanism (KZM) combines Kibble’s observation of topological defects formation in cosmological phase transitions with Zurek’s theory relating their density to critical slowing down, and hence to the universality class of a second-order phase transition. The resulting KZM predicts defect density as a function of the quench rate in second-order phase transitions, in both classical and quantum settings. It has applications across a wide range of fields, including condensed matter physics, cosmology, and quantum computing.
In this talk, I will discuss extensions of KZM beyond its original formulation. I will show how KZM can be combined with nucleation theory to describe weakly first-order phase transitions, how nonadiabatic excitation formulas can be generalized to exotic quantum phase transitions, and how order-parameter dynamics offers a new perspective on KZM. I will also discuss how machine learning can provide deeper insight into second-order phase transitions beyond the conventional KZM framework.連絡教員：物理学系 藤井 啓資（内線2136）
https://www.phys.sci.isct.ac.jp/wp/wp-content/uploads/2026/05/444.pdf
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セミナー
2026.05.19
講師：Professor Miyatsu Tsuyoshi（Soongsil University, Seoul, Korea）
日時：令和8年6月８日（月）16:00-
場所：本館2階 227C 物理学系輪講室The quark-meson coupling (QMC) model describes nuclear many-body systems in terms of quark degrees of freedom. In this model, quarks are confined inside each baryon and interact self-consistently with scalar- and vector-meson fields generated by the surrounding nuclear medium. As a result, the internal structure of baryons changes with density, producing density-dependent effective masses and baryon-meson couplings. This mechanism offers a microscopic interpretation of nuclear saturation and provides a natural bridge between baryon structure and nuclear many-body dynamics.
In this seminar, I will review the basic idea of the original QMC model and its applications to nuclear matter and finite nuclei, following the developments summarized in the review by Saito, Tsushima, and Thomas. I will then discuss several extensions and applications, including hyperonic matter, chiral effects, neutron-star equations of state, and the role of Fock terms and tensor couplings in dense matter. Finally, I will introduce a recent development toward quarkyonic matter, where baryonic and quark degrees of freedom coexist in a high-density regime. This talk aims to clarify how in-medium baryon structure variations can connect finite nuclei, dense matter, neutron stars, and possible quarkyonic phases within a common microscopic perspective.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/2026/05/443.pdf
