応用物理学輪講 I
6月11日
[注意事項]
発表の10日前までに宛てに「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6月11日(金)16:50〜

Aグループ

座長
張 灵飛
指導
教員名
川﨑 雅司 教授
発表者名 清水 祐樹
指導教員名 齊藤 英治 教授
発表題目(英語) Numerical study on parametric excitation
要旨(英語) In spintronics, the field of research on statistical fluctuations of magnons, which are quantization of spin waves, has been developing recently. In this field of magnonics, non-Gaussian noise distributions beyond the conventionally assumed Gaussian fluctuations due to nonlinearities are of great interest. In this presentation, I will discuss parametric excitations, which are nonlinear phenomena, including fluctuations, by numerically solving the master equation, which is the time evolution of the density matrix.
発表言語 日本語
発表者名 清水 龍之介
指導教員名 岩佐 義宏 教授
発表題目(英語) Nonreciprocal transport in twisted van der waals magnet
要旨(英語) Two-dimensional van der Waals crystals and van der Waals interface are characteristic material platforms of unique functionalities and novel physics. The recent emergence of 2D van der Waals magnets opens new possibilities for exploring new exotic physical phenomena and application for spintronics. For example, emergent phenomena have been observed in heterostructures formed by monolayer WSe2 and magnetic insulator CrI3. In addition, these days, symmetry engineering in van der waals interfaces is focused on as the new research viewpoint.
 To further study exotic physical properties originating from van der Waals interfaces using 2D magnets and symmetry engineering in van der waals interfaces, we performed transport studies on the interface of twisted van der waals magnet.
発表言語 日本語
発表者名 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.
 We have fabricated stacked magnets using EuBCO coated conductor with BaHfO3 nanorods (Fujikura Ltd.). In the previous study [1], we observed extended regions of irregular flux penetration called “flux jet” [2] originated by cutting-induced damages of coated conductors in magneto-optical images. When we compared the experimental results with the calculation result of trapped fields of the stacked magnet, there was discrepancy between them, and it can be understood by considering the reduction of the effective size of the stacked magnet due to the flux jet. In order to obtain better stacked magnet than the previous study, we improved the fabrication process so that the effect of cutting-induced damages in coated conductors becomes minimum. As a result, we have succeeded in magnetizing the stacked magnet than previous study and trapping 16.5 T of field at 10 K.
 I will also discuss the plan to obtain a higher trapped field in the future study.
[1] M. Suyama et al., Supercond. Sci. Technol. 34 065004 (2021).
[2] A. Gurevich et al., Phys. Rev. B 62 4004 (2000).
発表言語 日本語

Bグループ

座長
周 芝苑
指導
教員名
中島 多朗 准教授
座長
王 佳晨
指導
教員名
為ヶ井 強 准教授
発表者名 澤田 太郎
指導教員名 沙川 貴大 教授
発表題目(英語) Several anomalous phenomena from exceptional points
要旨(英語) In recent years, the physics of non-Hermitian systems attracts much attention, as it has been revealed that unusual phenomena which cannot be observed in Hermitian systems can appear in non-Hermitian systems. In particular, band structure with exceptional points emerging in non-Hermitian systems predicts singular (i.e., divergent) behavior of characteristic quantities. Non-Hermitian nature of physical systems typically originates from non-equilibrium property such as gain-loss structure.
 In this presentation, I will introduce the concept of exceptional point and review some known phenomena such as enhanced sensitivity and unidirectional invisibility. I will then present my theoretical observations, which suggests that simultaneous exceptional points of the band structure lead to a novel class of singular phenomena. In particular, some numerical results for unidirectional invisibility will be shown.
発表言語 日本語
発表者名 住谷 大志
指導教員名 小林 洋平 教授
発表題目(英語) The development of laser in glass using direct laser writing
要旨(英語) The femtosecond laser plays an important role in the industry of micromachining, for its ability to produce minuscule structure with smooth morphology. Recently, its usage had been limited to simple processing methods such as drilling and cutting, but complex processing methods that add functionality to materials such as superhydrophobic surfaces and waveguides are now attracting attention.
 Direct laser writing (DLW), the technology which makes waveguides by giving refractive index change to transparent materials like glasses, is one of these complex methods. DLW can help produce micro optical circuits of arbitrary structure, more easily than any other method. Applying this method to gain media doped glasses, one can even build a compact laser. However, this technology is still in development, because it is difficult to accurately predict the waveguide properties such as modes and losses from processing parameters and material properties, and is laborious to search the vast parameter space for the optimal condition that can generate the desired waveguides.
 In this presentation, I will discuss our plan on developing a laser based on laser-induced waveguides, and introduce the processing and measurement system.
発表言語 日本語
発表者名 園山 樹
指導教員名 古澤 明 教授
発表題目(英語) High performance photon-number-resolving detection
要旨(英語) In the field of optical quantum information processing, metrology and imaging, photon detectors which can count photons is required. However, compared to on-off detector which can discriminate only photon's absence, photon-number-resolving detector which can discriminate photon number is difficult to realize experimentally. In particular, photon-number-resolving detector that achieves both high time resolution and high photon number resolution has not yet been realized. This high performance photon-number-resolving detector can be applied to non-Gaussian state preparation which is needed for realizing optical quantum computation for example.
 So I have done research to achieve the high performance photon-number-resolving detector in two directions. First one is photon-number-resolving detection using Superconducting Nanostrip Photon Detector(SNSPD). And second one is photon-number-resolving detection using arraying SNSPD and Transition Edge Sensor(TES).
 In the presentation, I will talk about these two research results.
発表言語 英語
発表者名 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 ferromagnetic resonance observation
要旨(英語) Ferromagnetic resonance (FMR) spectroscopy is a canonical tool for probing spin dynamics. In nanoscale, however, the behavior of localized resonant modes has not been thoroughly understood yet owing to the difficulty in the local
measurement. We are working on the observation of FMR spatially resolved in atomic scale by using a scanning tunneling microscope (STM) combined with microwave measurement system.
 An STM enables us to probe local electronic states of a material’s surface by measuring the tunneling conductance 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 on local electronic spins, conventional electron spin resonance (ESR) technique using microwave has been integrated with SP-STM, which provides the new possibilities in controlling and probing spins in atomic scale. We apply this basic idea to ferromagnetic systems such as Co or Fe nano-island structures formed on
Au(111) substrate.
 In this presentation, I will discuss our methods and progress in the development.
発表言語 日本語