1. Clean Energy and Nano Convergence Centre (CENCON), Hindustan Institute of Technology and Science, 603103 Chennai, Tamil Nadu, India
2. School of Molecular Sciences, The University of Western Australia, Perth, Western Australia 6009, Australia
3. Condensed Matter Theory Group, Department of Physics and Astronomy, Uppsala University, Box
516, S-75120 Uppsala, Sweden
4. Applied Materials Physics, Department of Materials and Engineering, Royal Institute of Technology, (KTH), S-100 44 Stockholm, Sweden