2020 Fiscal Year Final Research Report

Visualization of atomic arrangement on the surface of topological Kondo insulators by low-energy positron diffraction

Research Project

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Project/Area Number	18H03476
Research Category	Grant-in-Aid for Scientific Research (B)
Allocation Type	Single-year Grants
Section	一般
Review Section	Basic Section 80040:Quantum beam science-related
Research Institution	High Energy Accelerator Research Organization (2020) National Institutes for Quantum and Radiological Science and Technology (2018-2019)
Principal Investigator	Wada Ken 大学共同利用機関法人高エネルギー加速器研究機構, 物質構造科学研究所, 准教授 (10401209)
Co-Investigator(Kenkyū-buntansha)	望月出海大学共同利用機関法人高エネルギー加速器研究機構, 物質構造科学研究所, 助教 (30579058) 白澤徹郎国立研究開発法人産業技術総合研究所, 計量標準総合センター, 主任研究員 (80451889)
Project Period (FY)	2018-04-01 – 2021-03-31
Keywords	低速陽電子ビーム / 低速陽電子回折 / 低速電子回折 / 表面
Outline of Final Research Achievements	Low-energy positron diffraction is a positron version of low-energy electron diffraction, and it has been proposed as an ideal method for analyzing crystal surface structures, even on surfaces containing heavy elements. However, it is difficult to obtain sufficient beam intensity for diffraction experiments due to the use of antiparticles. We have developed a low-energy positron diffractometer using an accelerator-based high-intensity slow-positron beam and have successfully observed diffraction patterns. The initial detector with a two-layer delay-line anode had a large cross-shaped dead area. We have developed a new low-energy electron/positron diffractometer using a three-layer delay-line anode to observe the diffraction pattern without the cross-shaped dead area. In addition, a surface structure analysis code for LEPD has been developed, which enables us to analyze the surface structure by LEPD.
Free Research Field	陽電子科学
Academic Significance and Societal Importance of the Research Achievements	次世代電子デバイスや先進触媒材料の研究分野において，物質の表面に発現する物理現象の研究は益々その重要度を増している。物質表面の特異な電子状態の観測やその他の機能計測と共に，それら物理現象の発現の源となる原子位置座標に関する研究は重要である。本研究成果によって，理想的な表面構造解析手法として提言されてきた低速陽電子回折法による表面原子位置座標の構造解析手法の整備が進んだことで，同手法による今後の応用研究の進展が期待できるようになった。