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

menu

内部学生向け(物工教務室)

応用物理学輪講 I

2020年11月6日(金)16:50〜 
Aグループ 
 座長:関根 孝彦、髙𣘺 知宏
Bグループ  
座長:曽根 和樹
氏名: 陶山 正裕
指導教員名: 為ヶ井 強 准教授
発表題目(英語): High-Field Magnet Using Stacked Coated Conductors
要旨(英語): Cuprate superconductors (RE)Ba2Cu3O7 (RE: Rare Earth, and it is called REBCO), which have higher critical current density than other superconductors at high temperatures and high fields, are expected to be used for superconducting cables and magnets. The commercially available REBCO coated conductors, which are thin tapes, can be cut and stacked to form a stacked magnet. To date, there have been many studies on stacked magnets because they can be applied for NMR, motor, etc. Our group fabricated a compact and high-field stacked magnet and succeeded in generating 13.6 T at 15 K .
 In this study, we fabricated a stacked magnet using EuBCO coated conductor with BaHfO3 nanorods (Fujikura Ltd.), and aimed at obtaining better stacked magnet than our previous study. We improved the fabrication process so that the effect of cutting-induced damages in coated conductors becomes minimum and guarantee better thermal conductivity by applying stronger force from above. We have succeeded in magnetizing the stacked magnet at lower temperatures than the previous study and trapping 14.1 T of field at 10 K. In addition to this, we succeeded in trapping high magnetic fields in shorter times.
 We will discuss the comparison of the experimental results and calculated trapped field based on the realistic Jc-H characteristics.
発表言語:日本語
氏名: 高木 寛貴
指導教員名: 関 真一郎 准教授
発表題目(英語): Search for antiferromagnetic materials with broken time-reversal symmetry
要旨(英語): Recently, the concept of spintronics, i.e. the technology that utilizes not only charge but also spin degree of freedom of electrons, has attracted attention as the key to enable the innovative devices with rich functionality.
 So far, the spintronics has mainly focused on ferromagnets, where their magnetization and associated time-reversal symmetry breaking allow us to retain, read and write magnetic information. On the other hand, the recent discovery of antiferromagnets with broken time-reversal symmetry suggests that the latter systems can be another platform for the next generation of spintronics.
 A typical example is Mn3Sn with non-collinear antiferromagnetic order which breaks time-reversal symmetry[1]. Despite its antiferromagnetic character, this compound shows giant anomalous Hall effect[1] and anomalous Nernst effect[2], which have previously been reported only in ferromagnetic materials with macroscopic magnetization. Mn3Sn has topological Weyl nodes in its electronic band structure due to time-reversal symmetry breaking [3], and the associated fictitious magnetic field generated via the quantum Berry curvature plays a role equivalent to magnetization. Such antiferromagnets with broken time-reversal symmetry are expected to have a similar function to ferromagnets due to their fictitious magnetic field, but also with potential advantages specific to antiferromagnets, such as the absence of a magnetization-derived stray field. However, there are still only a few reported examples of time-reversal symmetry broken antiferromagnets, and in particular, the one with the collinear antiferromagnetic order has not been established yet. [4,5]. Therefore, the further search of such materials systems is highly demanded.
 In this presentation, I will discuss the current status of our research on such time-reversal symmetry broken antiferromagnets.
[1] S. Nakatsuji et al., Nature 527, 212 (2015).
[2] M. Ikhlas et al., Nature Phys. 13, 1085 (2017).
[3] K. Kuroda et al., Nature Mat. 19, 1090 (2017).
[4] N. J. Ghimire et al., Nature Comm. 9, 3280 (2018).
[5] G. Tenasini et al., Phys. Rev. Lett. 2, 023051 (2020).
発表言語: 日本語
氏名: 園山 樹
指導教員名: 古澤 明 教授
発表題目(英語): Photon-number resolving detector for introducing non-Gaussian state into cluster state
要旨(英語): Our research goal is achieving universal and fault tolerant quantum computation. In order to obtain universality and fault tolerance, non-Gaussian state such as Cubic Phase State and GKP state is needed. In our group, we adopt measurement based computation. We have already demonstrated 2-dimensional cluster states which is the resource of universal quantum computation[1]. So our next step is introduction of non-Gaussian state into cluster state.
 For the preparation of various non-Gaussian state and for fast speed computation, we need fast time response photon number resolving detector. In previous research, photon number resolving detection using transition edge censor(TES) is popular. But recently, the fact that Superconducting nanowire Single Photon Detector(SSPD) can be used as a photon number resolving detector is confirmed[2]. Because SSPD is faster than TES, it is compatible with our research “introduction of non-Gaussian state into cluster state”.
 In this presentation, I will talk about the experiment of photon number resolving detection using SSPD.
[1] W. Asavanant,et al. Science 366, 373 (2019).
[2] Clinton Cahall ,et al. Optica 4,12(2017).
発表言語: 英語
氏名: 高原 規行
指導教員名: 川﨑 雅司 教授
発表題目(英語): Growth of EuxGd(1-x)TiO3 epitaxial thin films and its transport property
要旨(英語): Many of rare earth perovskite titanates (RTiO3) are consisted of trivalent R(=La, Gd…) and trivalent Ti, which takes 3d(1) electron configuration, and they are known to be the prototypical Mott insulators with orthorhombic distorted structure. But, exceptionally, EuTiO3 is a band-insulator with cubic perovskite structure  because Eu can get divalent state, which enables Ti to be tetravalent (3d(0)).
 In this study, we focus on the EuTiO3 and GdTiO3 whose both of A site ion (Eu2+ or Gd3+) take 4f(7)6s(2) electron configuration and have 7mu_B magnetic moment. By using the molecular beam epitaxy method, the epitaxial thin films of the solid solution between EuTiO3 (magnetic band insulator) and GdTiO3 (magnetic Mott insulator) are fabricated on LSAT or SrTiO3 substrates and we aim to study the metal-insulator transition of EuxGd(1-x)TiO3 by systematic control of Ti 3d orbital filling under the A site magnetic moment.
 In this presentation, I will briefly explain the research background and introduce the film fabrication and its transport property.
発表言語: 日本語 
氏名: 多賀 光太郎
指導教員名: 長谷川 幸雄 教授
発表題目(英語): The development of STM for electron spin resonance observation
要旨(英語): A scanning tunneling microscope (STM) is a powerful tool which enables us to probe the electronic state of a material’s surface by measuring the tunneling electrons between a sharp metal tip and the material. In particular, spin-polarized STM (SP-STM) can reveal the static spin structure on the surface with atomic resolution through the tunnel magnetoresistance effect between a magnetic tip and the sample.
 Recently, in order to obtain dynamic information of local electronic spins, conventional electron spin resonance (ESR) technique using microwave has been integrated with SP-STM, which provides the new possibilities of coherent control and probe of spins in the atomic scale.
 In this presentation, I will discuss the previous methods and our plans for development of ESR-STM.
発表言語: 日本語
氏名: 武田 和大
指導教員名: 賀川 史敬 准教授
発表題目(英語): Real space observation of intermittent and stochastic phase transition  kinetics
要旨(英語): Phase control between stable and metastable states are based on  comprehension of phase-transition kinetics. First-order phase transitions are often initiated by nucleation of a stable phase, followed by growth of it.  Although the nucleation events are stochastic, behaviors of the whole system can be understood as statistical expectations when many nucleation events contribute to the phase transition kinetics. Meanwhile, when a few nucleation is enough to  complete a phase transition, it is expected that the whole system behaves stochastically. However, such stochasticity is rarely examined experimentally in macroscopic systems.
 In the present study, we performed scanning Raman microscopy on the transition-metal dichalcogenide IrTe_2 , which exhibits a first-order charge ordering transition. We prepared a thin plate form of IrTe_2 so that the whole sample can be dominated by a few stochastic events. When the sample is kept at a certain temperature, a volume fraction of the most stable charge-ordered phase increases intermittently. The same procedure does not reproduce the time of intermittent events, indicating its stochastic nature. Thus, we found that a small sample exhibits intermittent and stochastic phase transition kinetics.
発表言語: 日本語 
氏名: 竹内 晴哉
指導教員名: 酒井 啓司 教授
発表題目(英語): Viscosity measurement under low shear rate by Electro Magnetically Spinning sytem
要旨(英語): Viscosity is a parameter that expresses the viscosity of a fluid, and is the ratio of shear stress and shear rate, whichIt is the ratio of the sliding speed to the sliding speed .Viscosity is one of the most important mechanical properties characterizing fluid dynamics. Viscosity values in most fluids are not always constant and depend on the shear rate.As it changes, it is required to measure the viscosity of various regions both industrially and physically necessity.However, in the conventional viscosity measurement technique, only the viscosity with a shear rate of about 100 n (/ s), which is the lowest, can be measured.Therefore, in this presentation, we will present a method for measuring viscosity at a shear rate of 10n (/ s) using the newly developed EMS system.
発表言語:日本語
氏名:
指導教員名:
発表題目(英語):
要旨(英語):
発表言語: