1999 Fiscal Year Final Research Report Summary
Quantum diffusion and Bloch waves of atoms in solids
| Project/Area Number |
08240106
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| Research Category |
Grant-in-Aid for Scientific Research on Priority Areas
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| Allocation Type | Single-year Grants |
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| Research Institution | Chuo University |
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Principal Investigator |
FUKAI Yu Department of Physics, Chuo University Professor, 理工学部, 教授 (80055136)
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| Co-Investigator(Kenkyū-buntansha) |
KADONO Ryosuke Institute of Materials Structure Science Professor, 教授 (10194870)
YAMADA Kousaku Department of Physics, Kyoto University Professor, 理学研究科, 教授 (90013515)
SUGIMOTO Hidehiko Department of Physics, Chuo University Professor, 理工学部, 教授 (00187668)
HIGEMOTO Wataru Inst. of Physical and Chemical Research Res. staff, ミュオン科学研究室, 研究員
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| Project Period (FY) |
1996 – 1998
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| Keywords | Quantum diffusion / Hydrogen in metals / muon / muonium / NMR / μSR |
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| Research Abstract |
Fukai aimed at developing a new arena of quantum diffusion in solids, and decided to focus on hydrogen atoms trapped by vacancies in metals. He started by doing systematic experiments on the superabundant vacancy formation, i.e. the formation of a large number of vacancy-hydrogen clusters in metals, and tried to determine their thermal-equilibrium concentrations, their sources and kinetics of formation, their dependence on metal species, etc. By these systematic investigations and theoretical developments (also made by Fukai), the phenomenon of superabundant vacancy formation was clarified adequately, and has become predictable and controllable. Thus he selected the Nb-H system as the most suitable one for the present purpose, and performed NMR measurements down to liq.He temperatures. A proton signal motionally narrowed below 20 K was observed and was attributed to a cage motion of hydrogen atoms trapped by vacancies. Possible quantum states and tunnelling motion of these protons are still under investigation.
Kadono consistently pursued a manifestation of the de Broglie wave nature of atoms in solids by μSR experiments at extremely low temperatures. He built a cryostat operative down to several mK, and measured μSR signals in a KCl crystal as a function of temperature and magnetic field. Novel features observed at the lowest temperature ( < 10 mK ) analyzed in terms of Kondo's theory (also developed during the same period) revealed unambiguously the Bloch character of muonium waves propergating in a KCl lattice. This is the first observation of such a wave nature of atoms in solids.
In this way, the two original aims of this research project have been accomplished to a large extent.
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