MOE Key Laboratory for Nonequilibrium Synthesis and Modulation of Condensed Matter;
Xi'an Jiaotong University;
Xi'an 710049;
CAS Key Lab Time&Frequency Primary Standard;
National Time Service Center;
Xi'an 710600;
Institute of Space Physics and Applied Technology;
Peking University;
Beijing 100871;
Rice University;
Department of Physics&Astronomy and Rice Institute;
Houston;
Texas;
USA;