State Key Laboratory of Surface Physics;
and Department of Physics;
Fudan University;
Shanghai 200433;
China;
Shanghai Qi Zhi Institute;
Shanghai 200232;
China;
Neutron Scattering Division;
Oak Ridge National Laboratory;
Oak Ridge;
Tennessee 37831;
USA;
Laboratory for Computational Physical Sciences(MOE);
Fudan University;
Shanghai 200433;
China;
Institute of Nanoelectronics and Quantum Computing;
Fudan University;
Shanghai 200433;
China;
Shanghai Research Center for Quantum Sciences;
Shanghai 201315;
China;