1. Department of Physics
2. Zhejiang Sci-Tech University
3. Hangzhou 310018, P.R. China
4. Department of Physics and ITPA
5. Xiamen University
6. Xiamen 361005, P.R. China
7. Leibniz-Institut für Polymerforschung Dresden
8. 01069 Dresden, Germany
9. Department of Engineering Materials University of Sheffield Mappin Street
10. Sheffield S1 3JD, UK
11. Technische Universität Dresden
12. Institute of Theoretical Physics
13. D-01069 Dresden, Germany