1. Research Institute of Superconductor Electronics, Nanjing University, Nanjing 210093, China
2. National Institute for Materials Science, Tsukuba 3050047, Japan
3. Electronics and Photonics Research Institute, Advanced Industrial Science and Technology, Tsukuba 3058568, Japan
4. Physikalisches Institut and Center for Collective Quantum Phenomena in LISA+, Universität Tübingen, Tübingen D-72076, Germany