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研究成果
2026.07.17
https://www.isct.ac.jp/ja/news/pqogqvqunmob
東京科学大学（Science Tokyo）理学院 物理学系の石塚大晃准教授らの研究グループは、量子ゆらぎと局所磁気相関の協奏効果により非線形電気伝導度（非相反電流）に特徴的な対数温度依存性が生じることを理論的に示しました。
本成果は、磁性金属における量子ゆらぎの効果が非線形輸送特性に与える影響について新しい理論的枠組みを与えるものであり、量子効果によるスピントロニクス素子の性能向上へと応用されることが期待されます。
本研究成果は、米国物理学誌「Physical Review Letters 」に2026年7月15日（米国東部時間）に掲載されました。 -
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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お知らせ
2026.07.09
日時：令和8年7月17日(金)17:15-18:15
場所：本館1階M123講義室
講師：西口大貴氏（理学院物理学系准教授）皆さんは、群れは好きですか？水族館で渦巻くイワシの群れを見て、何を考えますか？
自然界には、鳥の群れからバクテリアや細胞集団まで、様々なスケールの群れが存在します。これらの群れは、しばしばリーダーがいないにもかかわらず、秩序立った集団運動を示します。このような群れを一つの物質とみなし、そこに統計物理学的な観点から普遍法則を探究するのがアクティブマター物理学です。もっと物理的に定義すると、アクティブマターとは、個々の構成要素が自由エネルギーを力学的仕事へ変換して自ら運動するという非平衡な粒子の多体系です。つまり、非平衡な“分子”からなる物質の物性物理学がアクティブマター物理学です。
本談話会では、アクティブマターを概観したうえで、バクテリアや自己駆動コロイド粒子から培養細胞集団まで駆使することで、非平衡系における普遍法則や創発現象を実験から探る、我々の研究を紹介します。さらに、アクティブマターの新奇材料としての可能性や、発生生物学など生命科学への展開についても紹介します。https://www.phys.sci.isct.ac.jp/wp/wp-content/uploads/2026/07/r8_summer.pdf
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研究成果
2026.07.03
https://www.isct.ac.jp/ja/news/wrx6ltojyijx
東京科学大学（Science Tokyo） 理学院 物理学系の古田爽樹大学院生と賀川史敬教授（理化学研究所 創発物性科学研究センター チームディレクター）、理化学研究所 創発物性科学研究センター（CEMS）のYao Guang（ヤオ・グァン）特別研究員（研究当時）、軽部皓介ユニットリーダー、田口康二郎グループディレクター、小椎八重航上級研究員、于秀珍チームディレクターらの研究チームは、金属らせん磁性体であるCo8.5Zn8.5Mn3（コバルト・亜鉛・マンガン化合物）において、磁場下でらせん磁気構造の進む方向を電流で可逆制御できることを初めて実証しました。
本成果は、7月2日付（現地時間）の「Communications Materials」誌に掲載されました。
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お知らせ教員公募
2026.07.02
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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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研究成果
2026.06.10
Revealing optical activity in achiral crystals | Science Tokyo
Raman optical activity, long thought to require chiral molecules or magnetic order, has been demonstrated in an achiral, nonmagnetic crystal by researchers at Institute of Science Tokyo.
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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
