1. Department of Quantum Science and Energy Engineering, Tohoku University,, 01 Aramaki-Aza-Aoba, Sendai 980-8579, Japan, Tel.: +81-22 217 7923. E-mail address: akira.hasegawa@qse.tohoku.ac.jp (A. Hasegawa).
2. Department of Material Science, Japan Atomic Energy Research Institute, Tokai, 319-1195, Japan