Affiliation: | 1. Department of Physics, Yantai University, Yantai 264005, China2. School of Physics, Nankai University, Tianjin 300071, China3. Niologic GmbH, Max-Ernst-Str. 4, 50354 Hürth, Germany4. Institute for Theoretical Physics, University of Cologne, Zülpicher Str. 77a, 50937 Cologne, Germany |