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Strasser, P.*; 阿部 充志*; 青木 正治*; Choi, S.*; 深尾 祥紀*; 東 芳隆*; 樋口 嵩*; 飯沼 裕美*; 池戸 豊*; 石田 勝彦*; et al.
EPJ Web of Conferences, 198, p.00003_1 - 00003_8, 2019/01
被引用回数：13 パーセンタイル：98.93(Quantum Science & Technology)High precision measurements of the ground state hyperfine structure (HFS) of muonium is a stringent tool for testing bound-state quantum electrodynamics (QED) theory, determining fundamental constants of the muon magnetic moment and mass, and searches for new physics. Muonium is the most suitable system to test QED because both theoretical and experimental values can be precisely determined. Previous measurements were performed decades ago at LAMPF with uncertainties mostly dominated by statistical errors. At the J-PARC Muon Science Facility (MUSE), the MuSEUM collaboration is planning complementary measurements of muonium HFS both at zero and high magnetic field. The new high-intensity muon beam that will soon be available at H-Line will provide an opportunity to improve the precision of these measurements by one order of magnitude. An overview of the different aspects of these new muonium HFS measurements, the current status of the preparation for high-field measurements, and the latest results at zero field are presented.
下村 浩一郎*; 伊藤 孝
Journal of the Physical Society of Japan, 85(9), p.091013_1 - 091013_5, 2016/09
被引用回数：3 パーセンタイル：27.6(Physics, Multidisciplinary)Hydrogen in semiconductors and insulators plays a crucial role in their electric conductivity. Substantial experimental and theoretical efforts have been made to establish this hypothesis in the last decade, and the muon spin rotation technique has played a pioneering role. Positive muons implanted into such low-carrier systems often form a muonium (a hydrogen analogue). Although its dynamical aspect may be different from the heavier hydrogen, the electronic structure of the muonium is expected to be identical to that of hydrogen after a small correction of the reduced mass. Since the discovery of a shallow muonium in CdS, its properties have been intensively studied in many semiconductors and insulators, and then it was interpreted as a possible origin of 
-type conductivity under the context of a classical shallow donor model. In this article, we will describe the principle of muonium experiments and survey recent achievements in this field.
; Electronic structure of the hydrogen-like defects and their potential use in depth-resolved detection of oxygen vacancies伊藤 孝; 髭本 亘; 幸田 章宏*; 下村 浩一郎*
no journal, ,
Recent 
SR studies in SrTiO focusing on the following two aspects will be presented. (i) Electronic structure of interstitial Mu in SrTiO: The formation of a Mu
-Ti
polaron complex was observed upon implantation of positive muons into stoichiometric SrTiO. The small activation energy of 30(3) meV found for the thermal dissociation of the Mu-Ti polaron complex suggests that the strain energy required to distort the lattice is comparable to the electronic energy gained by localizing the electron. (ii) Potential use of SR for oxygen vacancy detection in SrTiO
: The oxygen vacancy (V
) is a major defect species in perovskite titanates, having a strong impact on their electrical, optical, and dielectric properties. In spite of the importance of the defect, experimental techniques that can directly detect V are still limited. Through a series of SR measurements on oxygen-deficient SrTiO we revealed that there is a clear positive correlation between the muon spin relaxation rate and the carrier concentration, which is expected to be roughly proportional to the V concentration. This, together with the variability of muon implantation depth, suggests that the SR spectroscopy is potentially suitable for the depth-resolved analysis of V distribution in perovskite oxides, which is complementary to cation vacancy-sensitive techniques, such as positron annihilation spectroscopy.
