1. Department of Physics and Astronomy, West Virginia University, Morgantown, West Virginia 26506, USA
2. Department of Physics, Indian Institute of Technology, Guwahati 781039, Assam, India
3. Key Laboratory of Functional Materials and Devices for Special Environments of CAS, Xinjiang Technical Institute of Physics and Chemistry, 40-1 South Beijing Road, Urumqi 830011, China
4. Leibniz Institute for Solid State and Materials Research (IFW) Dresden e.V., Helmholtzstr. 20, D-01069 Dresden, Germany