1. Key Lab of Materials Physics and Anhui Key Lab of Nanomaterials and Nanotechnology; Institute of Solid State Physics; Chinese Academy of Sciences; Hefei 230031 China
2. College of Chemistry and Pharmaceutical Sciences; Qingdao Agricultural University; Qingdao 266109 P. R. China
3. Key Laboratory of Modern Acoustics; MOE, Institute of Acoustics; Department of Physics; Nanjing University; Nanjing 210093 China