1. Research Institute of Superconductor Electronics, Nanjing University, Nanjing 210093, China
2. National Institute for Materials Science, Tsukuba 3050047, Japan
3. Physikalisches Institut and Center for Collective Quantum Phenomena in LISA+, Universität Tübingen, D-72076 Tübingen, Germany
4. Kotel'nikov Institute of Radio Engineering and Electronics, 125009 Moscow, Russia