1. Department of Physics, Indian Institute of Technology Patna, Bihta Campus, Patna-801106, India
2. The Bremen Center for Computational Materials Science (BCCMS), Universität Bremen, Am Fallturm 1, TAB Building, 28359 Bremen, Germany
3. Department of Microtechnology and Nanoscience, Quantum Device Physics Laboratory, Chalmers University of Technology, SE-412 96 Gothenburg, Sweden
4. Global Innovative Center for Advanced Nanomaterials, University of Newcastle, Callaghan, New South Wales 2308, Australia