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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
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セミナー
2026.05.19
講師：Dr. Heo Kyoungsu（Soongsil University, Seoul, Korea）
日時：令和8年6月８日（月）15:00-
場所：本館2階 227C 物理学系輪講室This talk introduces how nuclear potentials are used to understand low-energy nuclear reaction dynamics. In this energy region, reaction observables are strongly affected by nuclear structure, channel coupling, collective motion, cluster correlations, and breakup or fusion processes. Because many reaction channels can contribute coherently, a simple perturbative description is often insufficient as a complete reaction model. A practical strategy is to separate the reaction space into explicitly treated channels and effectively treated channels. The optical model potential accounts for the loss of elastic flux into non-elastic channels, while coupled-channel methods describe selected important excitations and reaction pathways more directly. Microscopic ingredients, such as folding potentials based on nuclear densities and effective nucleon-nucleon interactions, provide a useful bridge between nuclear structure and reaction observables.
The presentation also discusses how interference among different reaction amplitudes shapes the measured cross sections. Recent visualization approaches based on scattering amplitudes offer an intuitive way to interpret near-side, far-side, internal, and barrier-related components of the reaction. Overall, the talk aims to show how phenomenological, coupled-channel, and microscopic potential models can be combined to extract physical reaction mechanisms from low-energy nuclear scattering data.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/2026/05/442.pdf
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セミナー
2026.05.15
講師：Dr. Davide Bossini（University of Konstanz, Germany）
日時：令和8年6月1日（月）16:30-
場所：南5号館1階 103B第2会議室It has been proposed that magnetic waves in solids, i.e. spin waves or magnons, are promising information carriers for future information technology, enabling the processing of data at THz rates with limited energy dissipations. In this talk, I will briefly discuss how these excitations can be coupled to charges, highlighting recent progress involving processes at terahertz frequencies [1-2].
The main part of the talk will address the optical manipulation of magnons. I will show how resonant excitation of specific magnetic and electronic transitions drives the system into non-equilibrium states in which magnon modes, that are not directly excited, become activated and substantially modified. Two distinct physical scenarios will be discussed. In the first, optical excitation of electronic transitions modifies the magnetic anisotropy in a 20-nm-thick magnetic film, leading not only to the generation of coherent magnons but also to an on-demand frequency renormalization [3]. Both redshifts and blueshifts of the magnon frequency are achieved, reaching up to 40% of its equilibrium value at room temperature. In the second scenario, I will present an approach based on high-momentum magnons with wave vectors near the edges of the Brillouin zone, which can be resonantly driven using mid-infrared laser pulses. This excitation pathway activates distinct zone-center modes whose amplitudes and frequencies are strongly renormalized compared to their equilibrium values [4]. I will conclude by outlining future perspectives of this research direction, with the long-term goal of achieving arbitrary optical control over magnon dispersion relations in quantum materials.
References
[1] T. Mezger et al., Physical Review Letters 135, 076702 (2025).
[2] M. Cimander et al., Nature Communications 17, 1480 (2026).
[3] V. Wiechert et al., Nature Communications 17, 145 (2026).
[4] C. Schoenfeld et al., Science Advances 11, 25 (2025).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/2026/05/441.pdf
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セミナー
2026.05.15
講師：Professor Daisuke Takagi（University of Hawaii at Manoa, Honolulu, HI ）
日時：令和8年5月25日（月）10:30-
場所：南5号館5階 503CD 大会議室Bacteria disperse over time and space through random moves and turns. The dynamics of bacteria can be significantly altered in confined spaces of relevance to their native habitats. This talk presents some recent experimental observations of bacteria swimming in confined spaces. The results show surprising phenomena featuring bacterial escapes and migration. These behavioral responses are interpreted using basic physical and hydrodynamic principles. The findings suggest that the physical landscape can profoundly impact the dynamics and distribution of bacteria.
※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。
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/2026/05/119tokubetsu.pdf
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セミナー
2026.05.01
講師：川野 雅敬 助教 （東京大学 大学院総合文化研究科）
日時：令和8年5月18日（月）13:30-
場所：本館2階 290 物理学系輪講室The Hall effect is traditionally associated with the motion of charged particles subjected to an external magnetic field via the Lorentz force. Beyond this classical picture, Hall responses can also arise without an external magnetic field. In magnetic insulators, magnons, charge-neutral bosonic quasiparticles, can exhibit the thermal Hall effect through an emergent gauge field, without relying on the Lorentz force [1]. The thermal Hall effect is of fundamental importance as it provides a powerful probe of charge-neutral carriers and emergent gauge fields in quantum magnets.
In this seminar, I will discuss the realization of the magnon thermal Hall effect in two classes of systems where it was previously thought to be absent or strongly suppressed.
First, I will discuss the realization of this effect in edge-shared lattices, such as square and triangular lattices. The conventional U(1) gauge-field picture imposes a no-go condition that precludes the thermal Hall effect in these geometries [2,3]. We overcome this limitation by introducing a non-Abelian gauge-field picture, in which the noncommutativity of gauge fields generates an additional emergent magnetic flux [4,5]. This flux breaks effective time-reversal symmetry and enables the magnon thermal Hall effect even in edge-shared lattices.
Second, I will discuss the thermal Hall effect in a spin-gapped system: 1/3-plateau phase of a kagome antiferromagnet. Spin-gapped systems are generally expected to suppress low-energy transport due to the absence of mobile excitations. We demonstrate that this picture breaks down in the presence of strong geometric frustration. We observe the coexistence of two distinct types of quasiparticles: localized, magnetically neutral modes that contribute to longitudinal heat transport, and mobile magnetic excitations with topologically nontrivial bands, giving rise to a sizable thermal Hall effect [6].
References
[1] Y. Onose et al., Science 329, 297 (2010)
[2] H. Katsura et al., Phys. Rev. Lett. 104, 066403 (2010)
[3] T. Ideue et al., Phys. Rev. B 85, 134411 (2012)
[4] H. Takeda, M. Kawano et al., Nat. Commun. 15, 566 (2024)
[5] M. Kawano, Phys. Rev. B 112, L060403 (2025)
[6] H. Takeda, M. Kawano et al., submitted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/2026/05/118tokubetsu.pdf
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セミナー
2026.05.01
講師：Professor Martina Basini（Department of Physics, ETH Zurich, Switzerland）
日時：令和8年5月22日（金）16:30-
場所：本館2階 290 物理学系輪講室In the solid state, processes involving angular momentum and its transfer have underpinned numerous foundational phenomena in physics, including magnetism, the conventional and anomalous quantum Hall effects, and orbital magnetism. The advent of laser sources in the terahertz frequency range has opened new avenues for the coherent excitation of phonons that carry angular momentum and enable the exploration of angular momentum transfer among different subsystems. This emerging field has revealed a range of novel phenomena-such as the phonon Hall effect, ultrafast Einstein-de Haas effect, phonon Faraday effect, and phonon Zeeman effect [1, 2], highlighting the role of phonons in angular momentum dynamics.
In this seminar, I will present different methods for preparing an orbital angular momentum state for both IR-active and Raman-active phonons in centrosymmetric perovskites and discuss its coupling to macroscopic properties. Particularly, I will focus on (i) a phonon-associated, magnetic-like contribution generated in SrTiO3 and KTaO₃ by a strong circularly polarised terahertz field, resonant to its soft phonon [3] and, on (ii) evidence of terahertz-driven strain in LaAlO3, revealed by an unconventional decay in the angular momentum dynamics [4].
References
[1] M. Basini et al. Nature 628, 534 (2024).
[2] C. S. Davies et al. Nature 628, 540 (2024).
[3] In preparation, THz field-induced magnetic-like response in the quantum paraelectric diamagnet KTaO3.
[4] M. Basini et al. Phys. Rev. Lett. 136, 156902 (2026).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/2026/05/440.pdf
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お知らせ教員公募
2026.05.01
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セミナー
2026.04.10
講師：早澤 紀彦 氏（理化学研究所 開拓研究所及び光量子工学研究センター）
日時：令和8年5月7日（木）14:00-
場所：南5号館5階 503CD 大会議室The realization of optical microscopy capable of true nanoscale observation has long been a central goal in science and engineering. With the rapid development of nanomaterials and nanodevices in recent years, analytical techniques that can address increasing structural and functional complexity have become essential. In this context, optical microscopy offers unique advantages, including operation under ambient conditions without the need for cryogenic temperatures or high vacuum, as well as non-contact and non-invasive measurement capabilities.
Our research focuses on the development of advanced nanospectroscopy and sensing methodologies based on plasmonic resonances. The key advantages of plasmonic systems arise from two fundamental properties: the strong enhancement and the extreme localization of electromagnetic fields. These properties are critical for nanoscale measurements, as field localization improves spatial resolution, while field enhancement compensates for inherently weak signals originating from small volumes of material or limited numbers of molecules.
Plasmonic resonances can be broadly classified into two categories: (1) localized surface plasmon resonance (LSPR) and (2) propagating surface plasmon resonance (SPR). In this presentation, I will introduce representative nanospectroscopic techniques based on LSPR, such as tip-enhanced Raman spectroscopy (TERS), as well as sensing approaches based on SPR, including Goos–Hänchen and Imbert–Fedorov shifts (GHS and IFS) and the photonic spin Hall effect (PSHE).
Particular emphasis will be placed on the extension of these techniques to diverse experimental environments, enabling broader applicability to a wide range of target materials. Furthermore, beyond the pursuit of high spatial resolution, recent efforts toward achieving high temporal resolution and rapid sensing—particularly through terahertz (THz) spectroscopy—will also be discussed.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/2026/04/439.pdf
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セミナー
2026.04.09
講師：山本 博章 氏（東京科学大学 理学院 物理学系）
日時：令和8年4月23日（木）13:30-
場所：本館2階 227B 物理学系輪講室（暫定）最初の重力波観測から10年後の今と未来
約13億年前、宇宙で起きたブラックホール同士の衝突。その衝突によって生じた時空のゆらぎは、2015年に地球で初めて観測されました。本講演では、人類が初めて「宇宙の調べ」を聴いた重力波観測の舞台裏と、その画期的な意義について、アメリカで実際に研究開発に携わっていた講師が解説します。光では捉えられなかったブラックホール連星の世界が、なぜ今わかるようになったのか。原子よりも小さな揺れを測る最先端技術と、100年にわたる科学者たちの挑戦をご紹介します。さらに、この10年で進歩した観測技術の成果と、今後さらに数十年をかけて改良を重ね、より遠い宇宙を見つめようとする将来計画についてもお話しします。
連絡教員 宗宮 健太郎（内線3546）
https://www.phys.sci.isct.ac.jp/wp/wp-content/uploads/2026/04/438.pdf
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セミナー
2026.04.03
講師：渡辺 展正 氏（慶應義塾大学 自然科学研究教育センター ）
日時：令和8年4月20日（月）13:30-
場所：本館2階 290 物理学系輪講室（暫定）We propose first-principle calculations of an open system based on the real-time path integral formalism, treating the environment as well as the system of interest together on a computer. We focus on the Caldeira-Leggett model, which is well known, in particular, as a model of quantum decoherence. The calculation simplifies for typical initial conditions, and the relevant complex saddle point can be determined by solving a linear equation. The integration over the saddles can be performed analytically, and the reduced density matrix can be obtained by tracing out a large number of harmonic oscillators in the environment. In particular, we confirm the dependence of the decoherence time on the coupling constant and the temperature that has been predicted from the Lindblad-type master equation in a certain parameter regime. If time allows, we also discuss how to extend this framework to general models, e.g., by using the generalized Lefschetz thimble method to overcome the sign problem.
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/2026/04/437.pdf
