[1] Chinese Acad Sci, Inst Solid State Phys, Hefei 230031, Peoples R China
[2] Australian Natl Univ, Dept Theoret Phys, Res Sch Phys Sci & Engn, Canberra, ACT 0200, Australia
[3] Sichuan Univ, Dept Phys, Chengdu 610064, Peoples R China
[4] Univ Antwerp, Dept Phys, B-2020 Antwerp, Belgium