応用物理学輪講 I
5月24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
2024年5月24日（金）16：50～18：50

Aグループ

座長
宮本　尚樹
指導
教員名
吉岡　孝高　准教授
発表者名 小口　尚志
指導教員名 井手上　敏也　准教授
発表題目（英語） Epitaxial growth and magnetic properties of CrxTaSe2
要旨(英語) :
要旨（英語） Transition-metal dichalcogenide (TMD) is a group of layered materials labelled with MX2 (M: transition metal, X: chalcogen), which is a promising platform for 2D material research. The layers of TMD are bound together by weak van der Waals (vdW) forces, and various MX2 materials can host additional ions within the vdW gaps through the intercalation process. Our study focuses on the magnetic properties of the 3d transition-metal-intercalated TMD.
We fabricated thin films of Cr-intercalated TaSe2 by molecular-beam epitaxy (MBE). Cr1/4TaSe2 with the 2×2 superstructure could be grown by MBE. The post-growth annealing in ultrahigh vacuum enabled modulation of the superstructure pattern into √3×√3, which turned out to exhibit in-plane ferromagnetism with the finite out-of-plane component as revealed by the anomalous-Hall effect measurements. We also observed unusual magneto-transport properties characterized with the positive component with the out-of-plane fields. In the presentation, we will show those experimental results in detail, and discuss the similarities and differences between CrxTaSe2 and CrxNbSe2.
発表言語 日本語
発表者名 大村　洸翔
指導教員名 志村　努　教授
発表題目（英語） Independent modulation of phase, intensity, and polarization by double-phase dielectric metasurfaces
要旨（英語） Metasurfaces are two-dimensional optical elements that spatially modulate the phase, intensity, and polarization of light (wavefront modulation) by arranging sub-wavelength-sized structures (metaatoms) on a substrate. Recently, metasurfaces have been attracting increasing attention for their potential to make optical products such as cameras lighter and more space-saving. In previous studies of dielectric metasurfaces, most of them modulate two of phase, intensity, and polarization independently, and there are few studies that modulate all three independently. Therefore, we propose a dielectric metasurfaces that can modulate all three parameters independently by incorporating the double-phase concept used in holography.
発表言語 日本語
発表者名 片岡　大輔
指導教員名 川﨑　雅司　教授
発表題目（英語） Topological Hall Effect at heterointerfaces by proximity effect and fabrication of SrVO3/ErCrO3
要旨（英語） Topological Hall effect(THE) is an emergent magnetotransport phenomenon observed in magnetic metals with non-coplanar spin textures. Conducting electrons acquire the Berry phase from the spin texture and feel an emergent field proportional to its scalar spin chirality. This phenomenon has been reported in various materials, including those with skyrmion and spin-ice structures. However, most of these experiments have been performed on single crystals of magnetic metal, where it is challenging to independently  modulate the magnetic and metallic properties. Consequently, advanced experiments to understand the detailed nature of THE  have not been feasible. Recently, THE at heterointerfaces of magnetic insulators and nonmagnetic metals, resulting from the ‘proximity effect of emergent field’ has been reported, paving the way for controlling THE by modulating the parameters of the components. In my study, aiming to enlarge THE, SrVO3/ErCrO3 system is selected. I will talk about sample fabrication by Pulsed Laser Deposition (PLD)  and my future plans.
発表言語 日本語

Bグループ

座長
村田　好登
指導
教員名
高橋　陽太郎　准教授
発表者名 川本　知輝
指導教員名 香取　秀俊　教授
発表題目（英語） Miniaturization of an atom source with a magneto-optical trap in a square pyramidal configuration
要旨（英語） Optical lattice clocks can measure the transition frequency of reference atoms with an accuracy up to the $10^{-18} level, making them suitable for gravitational potential measurements on a centimeter scale. There is a growing initiative to make these clocks portable and facilitate remote comparisons of gravitational potentials. A key step toward this goal involves miniaturizing the magneto-optical trap (MOT), which is the initial step in the atomic cooling process of optical lattice clocks. To generate cold atoms in MOT, it is important to maintain the equilibrium of the radiation pressure inside the MOT.

We discovered that a configuration in which five laser beams are directed from each surface of a four-sided pyramid towards a specific point, meets the required conditions. This configuration can be realized by just one laser and one specially designed mirror, resulting in the miniaturization of an atom source. Based on this idea, we determined the optimal arrangement of both the laser and the magnetic field and set up the overall experimental system. In this presentation, we explain our concept of the a four-sided pyramidal MOT and show the latest results of our experiment.
発表言語 日本語
発表者名 葛西　章也
指導教員名 求　幸年　教授
発表題目（英語） Possible three-dimensional superstructures of magnetic hopfions
要旨（英語） A magnetic hopfion, characterized by the topological index called the Hopf number, is a three-dimensional (3D) topological spin structure, that can be regarded as a magnetic skyrmion string twisted and connected at both ends. The hopfion has attracted much attention in recent years due to its novel controllability stemming from the 3D nature and the emergent electromagnetic phenomena. To date, a single magnetic hopfion has been observed and its stability has been discussed. Furthermore, the magnetic hopfions can form a two-dimensional (2D) superstructure in a confined geometry with broken inversion symmetry. However, while a 3D superstructure was observed in a chiral liquid crystal, the magnetic analogue in a bulk spin system has been largely unexplored. In this study, we theoretically investigate the stability of bulk 3D superstructures of magnetic hopfions by performing large-scale energy optimization with automatic differentiation. We successfully construct a possible hopfion 3D superstructure at zero magnetic field, by introducing magnetic anisotropy.The superstructure can be viewed as a 3D complex of the skyrmion strings and the meron strings. Our finding is a landmark achievement that simultaneously facilitates experimental and theoretical research of the exotic 3D topological spin textures.
発表言語 日本語
発表者名 岡崎　淳哉
指導教員名 長谷川　幸雄　教授
発表題目（英語） Investigation of nanoscale surface transport properties at low temperature
要旨（英語） Two-dimensional electron systems (2DESs) such as van der Waals monolayer, surface systems have attracted a lot of interest because of their low dimensionality and reduced symmetry. Therefore, surface transport properties are one of significant subjects.
In order to investigate the surface transport properties, a scanning tunneling potentiometry (STP) method is a quite powerful tool, which enables us to visualize topography and electrochemical potentials simultaneously with a nanometer spatial resolution and a microvolt potential sensitivity.
However, most STP measurements are conducted at room temperature and without magnetic fields. Then we have performed STP measurements at low temperature and under magnetic fields to demonstrate unique transport properties in the specific conditions.
In this presentation, I will introduce an STP method and discuss the results at low temperature and under magnetic fields.
発表言語 日本語
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