応用物理学輪講 I
12月12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12月12日(金) 16：50～18：50

Aグループ

座長
西澤　優
指導
教員名
武田　俊太郎　准教授
発表者名 本林　凌
指導教員名 十倉　好紀　卓越教授
発表題目（英語） Giant two-component nonreciprocal transport uniquely revealed in a “low-Tc” cuprate
要旨（英語） High-Tc cuprate remain central to research not only for their high-Tc but also for their rich coexistence of competing and intertwined orders. Recently, charge order has been recognized as a universal phenomenon in cuprates. As a result, La1.6-xNd0.4SrxCuO4 (LNSCO), long studied as a system exhibiting particularly strong charge order, has attracted renewed interest. 

In LNSCO, a stripe order — in which charge and spin align unidirectionally — develops and strongly suppresses superconductivity. We focus on the possibility that stripe order induces broken symmetries and have carried out detailed nonreciprocal transport measurements. We observe exceptionally large nonreciprocal responses, indicating c-axis polar and chiral symmetry breaking. Moreover, we discovered that two distinct contributions with different characteristic magnetic-field ranges overlap in the signal. 

In this presentation, we will discuss possible origins of the symmetry breaking, the mechanism driving nonreciprocity with two components, and why the non-reciprocal response is so pronounced.
発表言語 日本語
発表者名 山内　あおい
指導教員名 齊藤　英治　教授
発表題目（英語） Enhanced magnon Kerr nonlinearity by shape magnetic anistropy
要旨（英語） The realization of quantum states using magnons, the elementary excitations of spin waves in ferromagnets, has attracted increasing attention in recent years. In particular, it is known that the direct generation of Schrödinger's cat states, which are macroscopic superposition states, is achievable through the interplay of parametric nonlinearity and Kerr nonlinearity. Although magnons intrinsically possess both parametric and Kerr nonlinearities, conventional materials exhibit small Kerr nonlinearity, which hinders the formation of quantum states. In this presentation, we report experimental results demonstrating a significant enhancement of the Kerr nonlinearity of magnons compared to conventional materials, achieved by controlling shape magnetic anisotropy.
発表言語 日本語
発表者名 山本　大雅
指導教員名 齊藤　英治　教授
発表題目（英語） Current control of polar order and nonreciprocal transport in charge-ordered material: Fe3O4
要旨（英語） Polar order in solids has been extensively studied in ferroelectric insulators as a key element for memory devices. In conductive materials, however, such polar order is generally considered "hidden" and uncontrollable because itinerant electrons screen the macroscopic polarization. Here, we report the electrical control and detection of microscopic polar order in the charge-ordered system magnetite (Fe3O4). Leveraging the broken inversion symmetry in the charge-ordered phase of Fe3O4, we utilized nonreciprocal transport as a sensitive probe for the polar orientation. We demonstrate that the sign of the nonreciprocal voltage can be reversibly switched by applying current pulses. This current-driven switching mechanism overcomes the screening limit of conventional field-driven methods. Our findings establish polar order in conductors as a new controllable degree of freedom, and we discuss the origin of the nonreciprocal transport in terms of electron correlation.
発表言語 日本語

Bグループ

座長
野田　源文
指導
教員名
関　真一郎　准教授
発表者名 吉岡　統理
指導教員名 福谷　克之　教授
発表題目（英語） Hydrogen Adsorption Properties on FeSi Surface towards Spin Injection
要旨（英語） Spin-dependent phenomena at surfaces and interfaces are crucial for realizing next-generation spintronic devices. Previous studies have advanced the understanding of surface spin dynamics using atomic beams, including demonstrating the spin dependence of hydrogen atom adsorption probability on the ferromagnetic Ni(111) surface and observing spin current-electric current conversion (the inverse Edelstein effect) by irradiating the topological insulator Bi₂Se₃ surface with a spin-polarized hydrogen atom beam (SPH).

In this study, we focus on the strongly correlated insulator FeSi (ferrosilicon) as a new candidate material following these efforts. While bulk FeSi is a nonmagnetic insulator, its surface exhibits a ferromagnetic metallic state at low temperatures and has been reported to possess a giant Rashba splitting originating from strong spin-orbit interactions. This unique surface state is expected to be an efficient site for the inverse Edelstein effect.

To perform spin injection experiments using SPH, it is essential to first understand the surface's chemical stability and adsorption behavior toward hydrogen atoms. Therefore, this study investigates the hydrogen atom adsorption characteristics on the FeSi surface and changes in its surface structure. The experiments employ low-energy electron diffraction (LEED) to identify the surface periodic structure and thermal desorption spectroscopy (TDS) to evaluate the adsorption energy and coverage.
発表言語 日本語
発表者名 吉村　広夢
指導教員名 小芦　雅斗　教授
発表題目（英語） Efficient magic state cultivation with lattice surgery
要旨（英語） In order to realize a fault-tolerant quantum computer (FTQC) capable of universal quantum computation, the generation of magic states is indispensable. Conventionally, magic states have been produced through magic-state distillation; however, the substantial spacetime overhead associated with this procedure has constituted a major bottleneck in the implementation of FTQC. Magic-state cultivation[1] is a novel and promising technique expected to circumvent these limitations. 
In this presentation, I will outline the principles of magic-state cultivation and introduce recent work that achieves additional resource reductions by incorporating lattice surgery into magic-state cultivation[2].

[1]C. Gidney, N. Shutty, and C. Jones, Magic State Cultivation: Growing T States as Cheap as CNOT Gates, arXiv:2409.17595.

[2]Y. Hirano, R. Toshio, T. Itogawa, and K. Fujii, Efficient Magic State Cultivation with Lattice Surgery, arXiv:2510.24615.
発表言語 日本語
発表者名 羅　偲予
指導教員名 香取　秀俊　教授
発表題目（英語） Cold atom preparation for an atom interferometer on strontium clock transition
要旨（英語） Atom interferometry exploits the wave-like nature of atoms to extract information about physical quantities. Atom interferometer’s superiority of sensitivity and accuracy enable highly precise metrology and atom interferometer has been applied to measurements of gravitational acceleration, gravity gradients, and rotational motion, among others.

Strontium clock atom interferometers have recently attracted attention as next-generation quantum sensors for searches for dark matter and the detection of gravitational waves. Their appeal lies in the exceptional stability offered by strontium’s ultra-narrow optical transitions, which provide long coherence times. At the same time, strontium optical lattice clocks have achieved fractional uncertainties at the 10⁻¹⁸ level and have demonstrated differential height measurements with centimeter-scale resolution. The similarity of the systems between these two devices opens possibilities for versatile quantum sensors. In particular, relativistic geodesy requires precise knowledge of both frequency and gravitational acceleration, making the combined clock–interferometer system significant.

In this work, we successfully generated sub-microkelvin strontium atomic clouds suitable for atom interferometry. This presentation will introduce the principles of atom interferometry and the methods used to produce and characterize ultracold atoms.
発表言語 日本語
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