1. Institute of Industrial Science, The University of Tokyo, Meguro, Tokyo 153-8505
2. Graduate School of Integrated Arts and Sciences, Hiroshima University, Higashi-Hiroshima, Hiroshima 739-8521
3. Department of Quantum Matter, Graduate School of Advanced Sciences of Matter, Hiroshima University, Higashi-Hiroshima, Hiroshima 739-8521
4. Institute for Materials Research, Tohoku University, Sendai 980-8577