1. Department of Physics, Indian Institute of Technology Roorkee 1 , Roorkee 247667, Uttarakhand, India
2. Department of Chemistry, Indian Institute of Technology Roorkee 2 , Roorkee 247667, Uttarakhand, India
3. Department of Physics, Indian Institute of Technology 3 , Hauz Khas, New Delhi 110016, India
4. Institute for Theoretical Solid State Physics, IFW Dresden 4 , Helmholtzstrasse 20, 01069 Dresden, Germany