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応用物理学輪講 Ⅰ

        
2017年6月16日(金)16:50~ 
62号講義室(2F) 
 座長:高梨 直人
64号講義室(2F)  
座長:山﨑 翔太、横田 涼輔
氏名: 小澤  孝 拓
指導教員名: 福谷 克之 教授
発表題目(英語): Metastable hydride of Pd and its anomalous electrical property
要旨(英語): Palladium is one of the hydrogen storage metals. In the 1970s, it was discovered that when Pd absorbs H, it behaves as a superconductor with a transition temperature of 10K. Very recently, a possibility of high-temperature superconductivity(HTS) has been indicated with a transition temperature as high as 54 K. Although this HTS may be related to a metastable state regarding the position and concentration of absorbed H atoms in Pd, the mechanism is not yet clear. The purpose of our study is to elucidate the structure and mechanism of the HTS of PdH.
 We tried to fabricate a metastable structure by low-energy hydrogen ion implantation at a low temperature where hydrogen atoms cannot usually diffuse into the bulk. We think that because of its excess energy, H can reach the metastable site and be trapped there at low temperature. The sample is a 5 nm-thick Pd thin film evaporated on a SrTiO3 substrate. We investigated the PdH by the 4-terminal resistance measurement and thermal desorption spectroscopy. In this presentation, I will talk about the anomalous resistance change observed upon PdH formation by low-energy ion implantation as compared to hydrogenation with H2 gas exposure.
発表言語: 日本語
氏名: 北井  賢吾
指導教員名: 田中 肇 教授
発表題目(英語):  Cooling-induced fracture of molecular glasses adhered to substrate
要旨(英語):  Fracture of molecular glasses have been investigated with the objective of researching fracture toughness.
 C.Travis Powell,Yinshan Chen and Lian Yu revealed in 2015 the relationship between temperature at fracture and fracture toughness of material by conducting the experiment using molecular glasses as sample.
 There was some research papers that reports existence of anomalous spiral pattern of fracture, but the mechanism that explains emergence of such pattern of fracture has yet to be defined.
 Today I will introduce the previous study of crack pattern in molecular glasses and results from my study regarding to observed phenomena of spiral cracks.
 Observation of process that molecular glasses fracture was conducted in various range of sample thickness and anomalous phenomena was observed such as extinguishment of spiral cracks.
発表言語: 日本語
氏名: 梶  智博
指導教員名: 芦原 聡 准教授
発表題目(英語): Strong-field effects in solids driven by mid-infrared laser pulses
要旨(英語):  Intense electric field E > 1 V/nm can drive humorous nonperturbative phenomena, called strong-field effects.In our research, we study the control of high harmonic generation (HHG), which is one of the strong-field effects, illuminated by mid-infrared laser pulses. The feature of HHG is that some gases or solids emit light with integer times frequency of the original light's frequency ω by driving electrons with optical electric field unlike the conventional second harmonic generation.Solids are superior to gases in ease of handling and high potential for practical electronics device in the future.Despite the fascinating features, a research of HHG in solids has not reached maturity in comparison to gases yet.
 In this presentation, I introduce basic principles related to our study, HHG in gases and solids.  And then, I discuss some experiments for solids and the future plans.
発表言語: 日本語
氏名: 北原  暁
指導教員名: 長谷川 達生 教授
発表題目(英語):  Low-voltage operation of organic thin-film transistors (OTFTs) composed of high-resolution printed silver electrodes, and prospect for fully printed OTFTs.
要旨(英語):  Fabrication of electronic devices by printing processes, which is called “printed electronics,” has been noticed due to its unique property such as low-cost, energy-saving and large area fabrication of electronic devices. Recently, we have developed a promising electrode printing technique, surface photoreactive nano-metal patterning (SuPR-NaP), which enables high-resolution, high-conductive and strong-adhesive silver electrodes by printing process. In SuPR-NaP technique, we can easily obtain the structure of “electrodes on a fluoropolymer insulator,” leading to relative simple fabrication of bottom-contact OTFTs.
 In my presentation, I’d like to report that, by applying ultra-thin fluoropolymer insulator film for SuPR-NaP technique, relatively large gate capacitance was obtained, and that OTFTs successfully operated with low voltage (less than 2 V). Besides, chemical conversion of printed electrode surface improved characteristics of OTFTs. Also, I’ like to talk about fabrication of organic semiconductor film by printing process, and future prospect of fully printed OTFTs.
発表言語: 日本語 
氏名: 金子  竜馬
指導教員名: 十倉 好紀 教授
発表題目(英語): Novel charge dynamics and thermoelectric effect in hole-doped pyrochlore iridates
要旨(英語): Pyrochlore iridates R2Ir2O7 (RIO, R=Rare earth) is known for a candidate for emerging Weyl semimetal(WSM) phase and indeed the various phenomena suggesting the existence of WSM are observed, such as the anomalous domain-wall conduction or the exotic magnetic transport. While the expectation for WSM raise an interest in RIO, the quantum criticality(QC) on the point of metal-insulator transition(MIT) temperature going to zero also attracts researchers’ attention in recent. This QC of RIO is suggested to be related to topological nature through a novel band structure, quadratic band touching, and it can induce anomalous critical phenomena or fluctuation of order parameter.
 In our research, we choose Pr2Ir2O7 for a target material, which has quadratic band touching at Γ point of its energy bands, and try to observe a coupling between the carrier and the topological QC explained above. As a result, we observed a large enhancement of thermoelectric effect and a generation of a highly flat energy band, through hole doping. 
発表言語: 日本語
氏名: 木村 祥太
指導教員名: 小林 洋平 准教授 
発表題目(英語): Offset frequency detection of multi-GHz mode-locked laser. 
要旨(英語): Large mode spacing of multi-GHz mode-locked laser attract attention due to some novel applications, such as calibration of astronomical spectrograph, breath diagnosis and arbitrary waveform generation. For these applications, the repetition frequency and the offset frequency of mode-locked lasers must be stabilized. Generally, stabilizing the offset frequency is difficult due to the difficulty of detecting it. To detect the offset frequency, high pulse energy (> 1 uJ) and high nonlinear media are needed. However, it is difficult to get enough pulse energy for the detection of the offset frequency in the range that the repetition rate exceeds 1 GHz. Recently, we succeeded detecting the offset frequency of the 2-GHz mode-locked laser at 1 um. It is the highest repetition rate which detects the offset frequency at 1 um. 
発表言語: 日本語 

 
 

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