1. Professor Emeritus, Kobe University, Kobe 657-8501, Japan
2. Department of Physical Science, Osaka Prefecture University, Sakai 599-8531, Japan
3. Faculty of Science and Technology, Gunma University, Kiryu, Gunma 376-8515, Japan
4. College of Engineering, Shibaura Institute of Technology, Saitama 337-8570, Japan
5. Condensed Matter Theory Laboratory, RIKEN, Wako, Saitama 351-0198, Japan
6. Graduate School of Material Science, University of Hyogo, Kamigori, Hyogo 678-1297, Japan
7. National Institutes for Quantum and Radiological Science and Technology (QST), SPring-8, Sayo, Hyogo 679-5148, Japan