1. College of Science Institute of Materials Physics and Chemistry Nanjing Forestry University Nanjing 210037 P. R. China
2. Theoretical Physics and Applied Mathematics Department Ural Federal University Mira Street 19 620002 Ekaterinburg Russia
3. Consiglio Nazionale delle Ricerche (CNR)—Istituto Officina dei Materiali (IOM) Laboratorio TASC in Area Science Park, S.S. 14 km 163.5 34149 Trieste Italy
4. Dipartimento di Fisica Università della Calabria via ponte Bucci cubo 31/C 87036 Rende Cosenza Italy
5. Institute of Physics Academia Sinica Nankang Taipei 11529 Taiwan
6. Center for Condensed Matter Sciences National Taiwan University Taipei 10617 Taiwan
7. Department of Physics Pennsylvania State University 104 Davey Lab University Park PA 16802‐6300 USA
8. Department of Physics Institute for Nanoscience and Engineering University of Arkansas Fayetteville AR 72701 USA
9. Dipartimento di Scienze Fisiche e Chimiche Università dell'Aquila Via Vetoio 10 I‐67100 L'Aquila Italy