今月中締切の記事
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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：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
2026.05.01
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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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
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セミナー
2026.03.30
講師：Professor Corentin Coulais（University of Amsterdam, Netherlands ）
日時：令和8年4月8日（水）10:30-
場所：本館2階 290 物理学系輪講室およびZoomWhen metals are magnetized, emulsions phase separate, or galaxies cluster, domain walls and patterns form and irremediably coarsen over time. Such coarsening is universally driven by diffusive relaxation toward equilibrium. Here, we discover a vibrational counterpart—wave coarsening—in active elastic media: vibrations emerge and spontaneously grow in wavelength, period, and amplitude, before a globally synchronized state called a time crystal forms. We observe wave coarsening in one- and two-dimensional mechatronic metamaterials and capture its dynamical scaling. We further arrest the process by breaking momentum conservation and reveal a far-from-equilibrium nonlinear analogue to chiral topological edge modes. Our results open new questions about the transient physics of systems with non-potential interactions and suggest an organizing principle for nonlinear waves in acoustics, optomechanics, living matter, and soft robotics.
＊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/K4FBE190TqeWm0CoObrn8Q
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※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」および
学術変革領域(A)「進化情報アセンブリによる生命機能の創出原理」との共催です。
連絡教員：物理学系 花井 亮（内線2070）・西口 大貴（内線2447）https://www.phys.sci.isct.ac.jp/wp/wp-content/uploads/2026/03/436.pdf
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セミナー
2026.02.27
講師：Dr. Ziga Krajnik（New York University, USA）
日時：令和8年3月3日（火）13:00-
場所：本館2階 290 物理学系輪講室One-dimensional models are a theoretical playground for the investigation of strongly interacting many-body dynamics that have in recent years become experimentally realizable. While mean-field methods and other standard approaches are not applicable, they can often be investigated with techniques of integrability and generalized hydrodynamics that have revolutionized our understanding of their large-scale behavior. Fluctuations around hydrodynamic values display remarkable robustness and have recently been observed to be anomalous, indicating additional processes besides normal diffusion.
We study a family of cellular automata with ballistically propagating charged particles and stochastic scattering. By mapping the dynamics to a “vacancy-dressed” stochastic six-vertex model we derive the exact anomalous distribution of the charge current. Building on macroscopic fluctuation theory, we also give a hydrodynamic description of the model’s anomalous fluctuations. Linear degeneracy arising from charge inertness allows for simultaneous contributions from convective and normal diffusion.
Similar phenomenology of dynamical criticality is observed in equilibrium spin current fluctuations in the easy-axis and isotropic regimes of the XXZ spin chain. The easy-axis regime supports the non-Gaussian distribution of the charged single-file class despite not manifestly satisfying a kinetic constraint. We argue anomalous fluctuations instead arise due to linear degeneracy of the vacuum polarization in the quasi-particle description. At the Heisenberg point the spin structure factor matches that of the Kardar-Parisi-Zhang universality class while spin fluctuations are anomalous but distinct from those of the KPZ class.連絡教員：物理学系 笹本 智弘（内線2736）
https://www.phys.sci.isct.ac.jp/wp/wp-content/uploads/2026/02/435.pdf
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セミナー
2026.01.13
講師：Professor Ahn Jung-Keun（Korea University, Department of Physics, Korea）
日時：令和8年1月26日（月）15:00-
場所：本館2階 227C 物理学系輪講室およびZoom
Zoom：ID: 885 3110 9243 Pass：D5KLPPThis seminar will review experimental searches for the H-dibaryon through various reactions, focusing specifically on the latest results from the J-PARC E42 experiment. This experiment investigates the H-dibaryon near the Lambda Lambda and Xi- p mass thresholds. The E42 has collected thousands of Lambda Lambda production events from (K-, K+) reactions off a 12C target at 1.8 GeV/c. We are on the verge of publishing our results, and this talk will discuss the nature of the H-dibaryon, offering insights into exotic baryon spectroscopy and extending our understanding to further multiquark states.
連絡教員：物理学系 慈道 大介（内線2083）
https://www.phys.sci.isct.ac.jp/wp/wp-content/uploads/2026/01/434.pdf
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セミナー
2026.01.05
講師：中野 裕義 氏（東京大学 物性研究所）
日時：令和8年1月14日（水）15:30-【開始時刻変更】
場所：本館2階 290 物理学系輪講室Standard hydrodynamics serves as a successful macroscopic description of fluid motion, ranging from engineering applications to turbulent flows. However, this framework is inherently deterministic and neglects the fluctuations that inevitably arise due to their underlying atomic structure. In particular, these fluctuations govern fluid phenomena at the mesoscopic scale between the microscopic and macroscopic scales. Fluctuating hydrodynamics extends the classical description by incorporating thermal fluctuations, leading to a more accurate description of such mesoscopic transport phenomena.
Recently, we analyzed the strong non-equilibrium fluctuations exhibited by fluids subjected to uniform gradients, such as single-component fluids under a shear flow or a temperature gradient and multi-component fluids under a concentration gradient [1-3]. These phenomena are one of the most well-established examples requiring a fluctuating hydrodynamic description, having been precisely observed in microgravity experiments. We performed direct numerical simulations (DNS) of the fluctuating hydrodynamic equations, and investigated the properties of energy dissipation and fluid behavior in the inviscid limit. In this seminar, I will present these findings alongside a historical review of the development and analysis of fluctuating hydrodynamics.
[1] HN, and K. Yokota, Phys. Rev. E 111, L063401 (2025)
[2] HN, Y. Minami, and K. Saito, arXiv:2502.15241(2025)
[3] HN, and Y. Minami, arXiv:2511.17851 (2025)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/2026/01/433ーhenkou.pdf