1. Department of Physics, Arizona State University, Tempe, Arizona 85287-1504,
United States
2. School of
Physics and Electronic Engineering, Jiangsu Normal University, 221116, Xuzhou, People’s Republic of China
3. Condensed Matter Theory Group, Department of
Physics and Astronomy, Uppsala University, SE-751 20 Uppsala, Sweden
4. Applied Materials Physics, Department of Materials and Engineering, Royal Institute of Technology (KTH), SE-100 44 Stockholm,
Sweden
5. Department of Materials
and Environmental Chemistry, Stockholm University, SE-10691 Stockholm, Sweden