1. Walter Schottky Institute and Physics Department, Technical University of Munich, Am Coulombwall 4a, 85748 Garching, Germany
2. Munich Center for Quantum Science and Technology (MCQST), Schellingstr. 4, 80799 Munich, Germany
3. Institute of Physics and Beijing National Laboratory for Condensed Matter Physics, Chinese Academy of Sciences, 100190 Beijing, China
4. School of Physical Sciences, University of Chinese Academy of Sciences, 100049 Beijing, China
5. Songshan Lake Materials Laboratory, Dongguan 523808, Guangdong, China