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応用物理学輪講 Ⅰ

        
2017年10月20日(金)16:50~ 
62号講義室(2F) 
 座長:小坂 雄大、小澤 孝拓
64号講義室(2F)  
座長:梶 智博
氏名: 内田  太一
指導教員名: 長田 俊人 准教授
発表題目(英語): Spin current generation and detection on graphene
要旨(英語): Spintronics is a fascinating topic in recent physics, which is a technology using electron spin as information carrier. The spintronics is expected to have less energy loss because spin current does not cause Joule heating in contrast to ordinary charge current. Some studies focusing on controlling transport property of spin current have been reported, and it is known that the spin-orbit interaction (SOI) greatly affects spin relaxation length.
Because of its extremely small SOI, graphene has very long spin relaxation length, so that it is expected as a material for spin transport device. However, small SOI of graphene also result in difficulties of spin current generation and its detection. In this talk, I will talk about experiments for spin current injection into graphene, its detection, and futures if graphene as a spintronics device material.
発表言語: 日本語
氏名: 岡崎  大樹
指導教員名: 芦原 聡 准教授
発表題目(英語):  Development of a compact ultrafast light source in the Mid-IR
要旨(英語):  Ultrafast Mid-IR light sources are in great demand for various experiments such as nonlinear vibrational spectroscopy and strong field effects. So far, Ti:Sapphire laser, regenerative amplification, and OPA/DFG units are generally used as a light source for these experiments. However, these optical systems are complex and costly.
 Recent years, Cr or Fe doped II-VI chalcogenides are attracting a lot of attention as alternative ultrafast light sources directly emitting in the mid-IR. In my research, for the first step to realize a compact experiment system in the mid-IR region, I am developing a Kerr-lens mode-locked Cr:ZnS laser. In this talk, I will introduce some fundamentals about these topics and mention the progress of my research.
発表言語: 日本語
氏名: 大川  尭郁
指導教員名: 石渡 晋太郎 准教授
発表題目(英語): Synthesis of the carrier doped infinite layer cuprate and cuprate high temperature superconductors
要旨(英語):  After the first discovery of cuprate high-temperature superconductors by IBM researchers Georg Bednorz and K. Alex Müller in 1986, many researchers have studied cuprate high temperature superconductors.The highest Tc of cuprate superconductors reported so far is above 150K at high pressure. All of the cuprate superconductors have copper-oxide (CuO2) layers and it is thought that this layers play a principal role in superconductivity. Some cuprates such as CaCuO2 or SrCuO2 have CuO2 layers and therefore have the potentioal of superconducting. We have studied their physical properties under the high-temperature and high pressure conditions. Especially, I have studied hole-doped CaCuO2 and this study is aimed at discovering new cuprate supercondunctor by using high pressure apparatus called cubic anvil type high pressure high temperature device.In this presentation, I will introduce the basis of cuprate superconducting and the method to generate carrier-doped cuprate materials.
発表言語: 日本語 
氏名: 岡本  史也
指導教員名: 古澤 明 教授
発表題目(英語):  All-optical storage of superimposed states
要旨(英語):   A quantum memory is essential for realizing scalable quantum computation and communication. So far, some experiments of the quantum memory using atoms have been demonstrated. Whereas, there are some all-optical memories, which consist of optical cavity or optical fiber. In these schemes, the wavelength is not limited by transition energy of atoms, so they can be applied to communication wavelength band. Therefore, all-optical quantum memory is practically important.
 There are some experiments of all-optical quantum memory. For example, an experiment of heralded single-photon storage using optical cavity has been demonstrated. In that experiment, by using two concatenated cavities, a single-photon state is generated in the cavity by detecting a herald photon, and the state is stored. In this scheme, phase information of the state is not stored since it is phase-insensitive. However, photon-number superimposed states are phase-sensitive, and for application, it is necessary to store these states with their phase information kept.
 Here, we propose the scheme of all-optical storage of superimposed states. It is based on single-photon storage with two concatenated cavities. One is an optical parametric oscillator (OPO), and in the OPO, a photon pair, signal photon and idler photon, is generated by non-degenerate parametric down conversion. The other cavity is a shutter cavity. It determines which photon passes through it. The signal photon stays in the OPO, and the idler photon passes through the shutter cavity. The idler photon is displaced, and finally detected by a photon detector. Then a superposition of vacuum state and single-photon state is induced in the OPO. The superimposed state is emitted after storage time we set. The emitted state is phase-sensitive, so we verified the emitted states by phase-sensitive homodyne tomography. In conclusion, we succeeded in experimentally demonstrating storage of superimposed states including its phase information.
発表言語: 英語 
氏名: 大黒  文和
指導教員名: 長谷川 幸雄 准教授
発表題目(英語): Development of ESR-STM 
要旨(英語): Scanning tunneling microscope (STM) is a powerful instrument in nanoscience that enables local spectroscopy with atomic resolution. In addition to electronic information, STM can also provide magnetic information by detecting spin-polarized tunneling current (SP-STM). Now, by using such a locality on atomically resolved ESR (ESR: electron spin resonance) measurement, our laboratory is developing an ESR-STM that is applicable for observation of nanoscale ferromagnetic resonance, spin excitation of a single electron, etc. While SP-STM (or ordinary STM) measurement is conducted for stationary spins, ESR-STM allows us to obtain spin dynamics, which complements stationary information taken by former STMs. Here, I will introduce various types of STMs mentioned above and explain how the ESR-STM system can be realized.
発表言語:  日本語
氏名: 荻野 槙子
指導教員名: 高橋 陽太郎 准教授
発表題目(英語):  Gyrotropic birefringence on electromagnon driven by exchange-striction in multiferroic perovskite manganite
要旨(英語):  According to classical electromagnetism, static electric field and magnetic field are independent of each other. However, some materials show magnetoelectric effect, in which electric polarization is induced by magnetic field and magnetization is induced by electric field. In particular, gigantic magnetoelectric effect occurs in multiferroics represented by perovskite manganite because of its ferroelectricity generated by spin order. The effect also appears in optical response of material (Optical magnetoelectric effect, OME). This time, we focus on gyrotropic birefringence out of OME. The phenomenon is rotation of optical axis arising from magnetoelectric coupling. It has odd parity about the direction of optical propagation, electric polarization, and magnetization, so the direction of rotation of optical axis can be controlled by inversion of these degrees of freedom. Gigantic effect is expected to occur by using an electromagnon resonance, a magnetic resonance originated from frustration of magnetoelectric coupling. In this research, we observed gyrotropic birefringence taking advantage of electromagnon resonance driven by lattice distortion induced by magnetic exchange interaction.
発表言語: 日本語 

 
 

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