応用物理学輪講 I
10月29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
2021年10月29日(金)16:50〜

Aグループ

座長
澤田 太郎
指導
教員名
沙川 貴大 教授
座長
清水 祐樹
指導
教員名
齊藤 英治 教授
発表者名 大西 嘉祐
指導教員名 川﨑 雅司 教授
発表題目(英語) Fabrication and characterization of pyrochlore oxide hetero-interfaces Pb2Ru2O6.5/ Dy2Ti2O7
要旨(英語)  Dy2Ti2O7 is a ferromagnetic insulator that exhibits 2-in/2-out and 3-in/1-out states at low temperatures, which are called “spin ice” materials. These 2-in/2-out and 3-in/1-out states have scalar spin chirality and are expected to exhibit the topological Hall effect. On the other hand, Pb2Ru2O6.5 is a paramagnetic metal that retains its metallicity down to low temperatures. In this work, Pb2Ru2O6.5/ Dy2Ti2O7 hetero-interfacial thin films were fabricated on YSZ (111) substrate by pulsed laser deposition method to measure the transport properties of the insulator material Dy2Ti2O7. In this presentation, we will discuss the respective physical properties of Pb2Ru2O6.5 and Dy2Ti2O7, the results of transport properties and the optimization of the thin film fabrication.
発表言語 日本語
発表者名 梶原 駿
指導教員名 岩佐 義宏 教授
発表題目(英語) Fabrication of layered magnetic material and two-dimensional magnetism by Using the molecular beam epitaxy method
要旨(英語)  In this study, I used the molecular beam epitaxy method (MBE) to prepare a substance in which a magnetic element was intercalated into a transition metal dichalcogenide (TMD) and evaluated its physical properties. A compound consisting of Cr and Te was prepared, and it was clarified that this was Cr3Te4 in which 0.5 Cr was intercalated between the layers of CrTe2. By evaluating its magnetic properties, it was found that the thick film exhibits room temperature ferromagnetism (Tc~310K).On the other hand, Tc decreases to 200 K in the two-dimensional limit (three layers). We also discovered a new phase in which Tc is constant (160 K) up to the two-dimensional limit (two layers) by changing the film forming conditions.
 The results indicate that it is possible to develop various material phases by using MBE for TMD crystal growth. By developing various combinations of materials in the future, it is expected that it will lead to the development of two-dimensional physical properties of intercalated TMD.
発表言語 日本語
発表者名 齋藤 真幸
指導教員名 中村 泰信 教授
発表題目(英語) Measurement of single photon state by exploiting Brillouin scattering
要旨(英語)  Interfacing a single photon with another quantum system is a key capability in modern quantum information science. It has the potential to enable us to prepare and manipulate the quantum system by photon counting, and transfer it over long distances.
 In my presentation, I will introduce the well-known DLCZ protocol[1] and a related previous research[2], in which non-classical correlations between single photons and phonons were observed by using the behavior of Stokes and anti-Stokes process of Raman scattering. I will also give an explanation of the experimental scheme to achieve photon-phonon interference by using Brillouin scattering in optical fiber, and introduce the experiments of Brillouin scattering I have done so far.

[1] L.-M. Duan et al., Nature 414, 413 (2001)
[2] R. Riedinger et al., Nature 530, 313 (2016)
発表言語 日本語

Bグループ

座長
清水 龍之介
指導
教員名
岩佐 義宏 教授
座長
住谷 大志
指導
教員名
小林 洋平 教授
発表者名 沖上 和希
指導教員名 速水 賢 講師
発表題目(英語) Spiral states and skyrmion crystals under inter-orbital frustration
要旨(英語)  Magnetic skyrmions, topologically protected swirling spin textures, have drawn extensive interest as origins of emergent electromagnetic responses. So far, their stabilization mechanisms have been mainly investigated in noncentrosymmetric systems with the Dzyaloshinskii-Moriya interaction. On the other hand, the skyrmion crystals have recently been observed in several centrosymmetric magnets [1] that might be stabilized by frustrated exchange interactions [2] and/or higher-order exchange interactions that arise from the itinerant nature of electrons [3]. More recently, a new scenario stabilizing the skyrmion crystals in centrosymmetric systems has been proposed by considering the inter-orbital frustration on the basis of the ab-initio calculations [4], which implied that a competition between the ferromagnetic interaction originating from Gd-5d electrons and the antiferromagnetic interaction from Gd-4f electrons is important for the formation of the spiral state in the case of Gd compound [1]. As the skyrmion crystals consist of a superposition of three spiral states, one can expect that the skyrmion crystals can be stabilized in such a situation. Motivated by this implication, we examine the effect of the inter-orbital frustration on the stabilization of the skyrmion crystals. Specifically, we analyzed a bilayer triangular-lattice model with the different exchange interactions to mimic the inter-orbital frustration. I will discuss a possibility of the emergent skyrmion crystals in such inter-orbital frustration.

[1] T. Kurumaji et al., Science 365, 914 (2019).
[2] T. Okubo et al., Phys. Rev. Lett. 108, 017206 (2012).
[3] S. Hayami et al., Phys. Rev. B 95, 224424 (2017).
[4] T. Nomoto et al., Phys. Rev. Lett. 125, 117204 (2020).
発表言語 日本語
発表者名 黒川 亮
指導教員名 十倉 好紀 卓越教授
発表題目(英語) Spectroscopic study on topological electronic states in half-Heusler GdPtBi
要旨(英語)  The topological electronic state of matter is one of the most important topics in solid state physics. Recently, topological semimetals have attracted considerable interest because they show unique magnetic responses including giant anomalous Hall effect and negative magnetoresistance. In order to investigate the origin of such phenomena, I have performed the optical spectroscopy on topological materials. My target material is a zero-gap semiconductor RPtBi (R = rare-earth ions and Y) that hosts a band-inverted quadratic band touching point at the Brillouin zone center while is gapped in other momentum space. When the magnetic field is applied and the time-reversal symmetry is broken, the band degeneracy is lifted. As a result, the non-degenerate linear band crossings (Weyl points) show up in the momentum space, giving rise to salient magnetotransport properties. However, the electronic states in this family of materials are less explored so far and hence the direct evidence of Weyl fermions is indispensable. In this presentation, I will talk about the background of physical characteristics of Half-Heusler compounds and especially about my current result of the transport and optical properties in GdPtBi.
発表言語 日本語
発表者名 櫻井 快
指導教員名 木村 隆志 准教授
発表題目(英語) Soft X-ray microscopic imaging of living cells with a micro-solution holder
要旨(英語)  Many high-resolution microscopes have been developed and have shown great results. However, their application to living cells has generally been difficult because they require vacuum environments and fixation operations.
 I am working on the imaging of living cells by utilizing the following features of soft X-rays. First, soft X-rays are electromagnetic waves with a wavelength of about 1 nm, 1/100th that of visible light, which enables high spatial resolution. Second, soft X-rays have less interaction with cells than charged particles such as electrons, and living cells in liquid can be directly observed. Third, the distribution of elements and chemical states can be investigated using a spectroscopic technique called X-ray absorption fine structure.
 In this presentation, I will introduce the soft X-ray microscopy system installed at SACLA BL1, the Japanese X-ray Free Electron Laser facility, and the analysis of cell images using neural networks.
発表言語 日本語