10月10日 | 応用物理学輪講 I | 輪講 | 東京大学工学部物理工学科・大学院工学系研究科物理工学専攻

工学部物理工学科

応用物理学輪講 I

10月10日

[注意事項]
発表の10日前までに　office[at]ap.t.u-tokyo.ac.jp　宛てに「氏名」「指導教員」「発表題目（英語）」「要旨（英語）」「発表言語（英語または日本語）」を送付して下さい。

発表日: 2025年10月10日(金) 16：50～18：50

Aグループ

座長: 押金　こよみ
指導 教員名: 齊藤　英治　教授

座長: 香川　巧
指導 教員名: 高橋　陽太郎　准教授

発表者名	青木　幸一
指導教員名	山本　倫久　教授
発表題目（英語）	Edge Magnetoplasmons in Quantum Hall 2DEGs as a Platform for Flying Qubits
要旨（英語）	Edge magnetoplasmons (EMPs) are chiral collective charge excitations that propagate along the boundary of two-dimensional electron gases in the quantum Hall regime. Because of their robustness and tunability through gate structures, they offer a useful way to transfer and manipulate electronic signals coherently. In this talk, I will introduce the basic physics and control of EMPs and explain how they may be applied to the realization of electron flying-qubit architectures.
発表言語	日本語

発表者名	飽田　陽音
指導教員名	森本　高裕　准教授
発表題目（英語）	An effective magnetic field from chiral phonons
要旨（英語）	Chiral phonons are lattice vibrations where atoms rotate unidirectionally around their equilibrium positions. They can be induced by external stimuli such as laser pulses or temperature gradients. Recently, it has been shown that chiral phonons can generate a giant effective magnetic field, with theoretical predictions of over 100 T. Controlling magnetism in materials using this phenomenon is promising for ultrafast and energy-efficient spin manipulation, providing a new tool beyond conventional static magnetic fields. The theory of how chiral phonons produce this effective magnetic field has been studied through various models, such as the phonon analog of the inverse Faraday effect. This presentation will introduce these theories along with their corresponding experimental results.
発表言語	日本語

発表者名	阿讃坊　元
指導教員名	高橋　陽太郎　准教授
発表題目（英語）	Nonlinear gyrotropic byrefrigence in multifferoics
要旨（英語）	When spatial inversion and time-reversal symmetries are broken simultaneously, a linear coupling between static electric and magnetic field emerges via the magnetoelectric tensor. In light–matter interactions this coupling gives rise to nonreciprocal optical magnetoelectric effect(OME). Multiferroics in which electric polarization is induced by magnetic ordering intrinsically couple spin and ferroelectric degrees of freedom. In the terahertz (THz) range multiferroics exhibit giant OMEs originating from conventional magnetic resonances and from electrically active magnetic excitations, i.e., electromagnons. In this study, focusing on the multiferroic perovskite manganites Eu0.7Y0.3MnO3, known to exhibit a large linear OME response, we investigate the nonlinear extension of gyrotropic birefringence, namely, a nonreciprocal rotation of the optical axis.
発表言語	日本語

Bグループ

座長: 梶原　葵
指導 教員名: 求　幸年　教授

発表者名	荒木　良太
指導教員名	中村　泰信　教授
発表題目（英語）	Physics and Coherence of the Integer Fluxonium Qubit
要旨（英語）	Simultaneous protection from both energy relaxation and dephasing is a central challenge in superconducting qubit research for fault-tolerant quantum computers. Currently, we face a fundamental trade-off: transmon qubits protect against dephasing but not from energy relaxation, while fluxonium qubits can achieve protection from both at the π sweet spot but require bias lines that complicate integration. In this work, to resolve this trade-off, I explore an operational regime for the fluxonium circuit at zero bias point, which is called the "integer fluxonium". This regime achieves protection from energy relaxation by optimizing the fluxonium's parameters and reducing wave function overlap-crucially, without requiring the external magnetic field that hinders integration. In this presentation, I will explain the physics of the integer fluxonium and report the results of evaluation of the energy spectroscopy and coherence properties of the three-level system (qutrit), including the ground, first, and second excited states. This research offers new insights into the realization of protected qubits that combine both scalability and noise protection.
発表言語	日本語

発表者名	池田　大輝
指導教員名	関　真一郎　教授
発表題目（英語）	Anisotropic field-temperature phase diagram of zero magnetic field skyrmion material
要旨（英語）	Magnetic skyrmions are topologically protected magnetic structures characterized by a quantized skyrmion number. Not only are skyrmions of fundamental physical interest due to the colossal emergent electromagnetic field they exert on conduction electrons, but they also hold potential for application in high-density magnetic memory, as the skyrmions themselves behave as nanoscale particles that can be driven by small electric current. In particular, nanometer-sized skyrmions in centrosymmetric magnets stabilized by itinerant-electron-mediated interactions have garnered attention in recent years for their potential to realize high-density information storage. However, a major obstacle for practical application is that all currently known material systems require a large external magnetic field to generate the thermodynamically stable skyrmion phase. In this presentation, we will report on the detailed magnetic structure analysis of a single crystal of a material recently discovered in our laboratory that exhibits a skyrmion phase in the absence of a magnetic field. We will present the results of magnetization, electrical transport, and resonant X-ray scattering experiments conducted with magnetic fields applied along different symmetry axes.
発表言語	日本語

発表者名	石田　圭輝
指導教員名	塚﨑　敦　教授
発表題目（英語）	Kagome ferrimagnet Co3Mo films with flat band coming from Co-kagome lattice
要旨（英語）	Recent studies on 3d-transition-metal-based kagome-lattice materials have discovered rich emergent phenomena resulting from interactions between magnetism, nontrivial topological band structure, and electronic correlation [1]. Its unique geometry gives rise to characteristic band features: linearly dispersive Dirac bands, saddle points associated with van Hove singularities (VHS), and a dispersion-less flat band. Especially, Co-kagome materials such as CoSn [2] and Co3Sn2S2 [3] are typical examples exhibiting flatband-induced anisotropic charge transport and Weyl-point-mediated large anomalous Hall conductivity, respectively. Due to their exotic topological properties derived from band structure, kagome magnets are of great interest for the fundamental studies and hold immense promise for next-generation device applications. However, kagome metals with flat bands have been rarely explored in terms of utilizing its distinct characteristics for device functionality. In this presentation, I will introduce our successful fabrication of Co-kagome ferrimagnet Co3Mo films with perpendicular magnetic anisotropy (PMA) at room temperature. By applying band structure calculations and angle-resolved photoemission spectroscopy, we discovered that the Co-kagome flat bands are located close to Fermi energy. Furthermore, we investigated the effect of Pt-substitution in Co3Mo1-xPtx films to enhance PMA. These materials will open a new pathway for demonstration of magnetic devices based on topological concepts and for advancing flat-band physics. [1] J-X. Yin et al., Nature 612, 647 (2022). [2] H. Huang et al., Phys. Rev. Lett. 128, 096601 (2022). [3] E. Liu et al., Nature Phys. 14, 1125 (2018).
発表言語	日本語

応用物理学輪講 I一覧ページへ戻る