1. Division of Applied Physics, Graduate School of Engineering, Hokkaido University, N13 W8 Kita-ku, Sapporo 060-8628, Japan, Energy Technology Research Institute, AIST, 2-17-2-1 Tsukisamu-higashi, Toyohira-ku, Sapporo 062-8517, Japan, Research Institute of Instrumentation Frontier, AIST, Central 5, Higashi 1-1-1, Tsukuba 305-8565, Japan, and Institute of Low Temperature Science, Hokkaido University, N19 W8 Kita-ku, Sapporo 060-0819, Japan