応用物理学輪講 I
11月5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11月5日(金)16:50〜

Aグループ

座長
陶山 正裕
指導
教員名
為ヶ井 強 准教授
座長
園山 樹
指導
教員名
古澤 明 教授
発表者名 澤村 駿
指導教員名 高橋 陽太郎 准教授
発表題目(英語) Shift current by soft phonon excitation of SbSI
要旨(英語)  Recently, nonlinear electromagnetics in quantum materials has been studied because it provides the means to probe and control new phase of matter. Above all, "shift current", which can be accounted for in terms of geometric phase, has been attracting much attention. As apposed to the previous photovoltaic effect at the interface, shift current has defect tolerance, and its direction can be reversed by the rotation of the polarization of light. These features lead to new mechanism for generation of electricity.
 We focused on a ferroelectric semiconductor SbSI to measure shift current by soft phonon excitation under the radiation of terahertz pulses. In this presentation, I will explain the backgrounds of bulk photovoltaic effect including shift current. Then, the property of SbSI and the method of this research are introduced. After that, the results, which indicate large efficiency of the shift current, are shown. Finally, future plans for more precise computation of physical quantity are discussed.
発表言語 日本語
発表者名 正力 健太郎
指導教員名 高橋 陽太郎 准教授
発表題目(英語) Topological magneto-optical response in Dirac/Weyl semimetals
要旨(英語)  Light combines with magnetism to produce magneto-optical effects such as the magneto-optical Kerr effect and the Faraday effect. This effect has been applied to technologies such as optical isolators, magnetic domain imaging, and MO disks. Under these circumstances, in the field of material science, the concept of topology, which deals with invariant properties due to continuous deformation, has been attracting attention in recent years, and topological electrons such as Dirac/Weyl fermion have been found in the band structure of k-space.
 In recent years, it has been recognized that this Dirac Weyl fermion plays an important role in nonlinear optical responses such as high-order harmonic generation and photocurrent. Topological electronic structure can be regarded as having a magnetic monopole in the k-space, and it is expected that it will be strongly coupled with the magneto-optical response and new charge dynamics will be generated.
 In this presentation, we will introduce the characteristic charge dynamics of Dirac/Weyl fermion coupled with magnetism.
発表言語 日本語

Bグループ

座長
多賀 光太郎
指導
教員名
長谷川 幸雄 教授
座長
高木 寛貴
指導
教員名
関 真一郎 准教授
発表者名 末包 海
指導教員名 香取 秀俊 教授
発表題目(英語) Development of a compact, high-power 813 nm laser
要旨(英語)  Optical lattice clocks are atomic clocks with a stability of 18 orders of magnitude over several hours of measurement, and since clocks with 18 orders of magnitude stability can also function as "gravitational potential meters" capable of measuring height differences of 1 cm, they are expected to be applied to relativistic geodesy. In order to improve the portability of the clock for applications, I have miniaturized and increased the power of the 813 nm laser that forms the optical lattice.
 First, I will explain the principle of optical lattice clocks and the conditions required for the optical lattice. Then, I will explain the configuration of the laser and the performance evaluation of the obtained laser. Finally, a summary and future prospects are given.
発表言語 日本語
発表者名 高木 翼
指導教員名 石坂 香子 教授/小川 直毅 委嘱教授
発表題目(英語) Topological photocurrent
要旨(英語)  There are a variety of nonlinear optical effects in solid including bulk photovoltaic effect, harmonic generations, optical rectification, and nonlinear Kerr rotations. They are typically realized by light irradiation on non-centrosymmetric materials that results in nonlinear polarizations of electron systems. These phenomena are of great importance in studying excited-state physics s of the system as well as for applications in optical devices and solar cells.
 Recent studies have revealed that the geometry or topology of the electronic wave function in crystals, especially their phase factors, can describe remarkable physical phenomena such as ferroelectricity, nonlinear optical effects, and quantum and spin Hall effect. So-called topological photocurrent, including shift current and injection current, is such a nonlinear optical effect driven by the phase (Berry phase) of a wavefunction. Further understandings of these topological currents are highly demanded from not only fundamental, but also practical point of view.
 In this presentation, I will introduce the above topological photocurrents and discuss present status of my research on shift- and injection current spectroscopy on ferroelectrics and topological material. As for experiments, I’ll talk about the results on MnBi2Te4, an antiferromagnetic Weyl semimetal which predicted to give a giant photocurrent.
発表言語 英語
発表者名 高橋 安德
指導教員名 賀川 史敬 准教授
発表題目(英語) Exploration of the relationship between phase diagram and metastable states
要旨(英語)  In recent years, in controlling electronic states, a kinetic approach (especially rapid cooling) using metastable states has been made in addition to the usual thermodynamic approach of controlling parameters such as pressure and chemical composition. However, it is not known what materials can produce metastable states using rapid cooling. Therefore, we focused on the relationship between the phase diagram and the metastable state feasibility.
 In this study, focusing on phase competition, we were able to achieve a metastable state with W-doped VO2. In this presentation, I will talk about the mechanism of metastable state by rapid cooling and the experimental results.
発表言語 日本語