1. Department of Physics, Indian Institute of Technology Bombay, Mumbai 400076, India
2. Solid State Physics Division, Bhabha Atomic Research Centre, Mumbai 400085, India
3. Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai 400005, India
4. Helmholtz-Zentrum Berlin, Hahn-Meitner Platz 1, 14-109 Berlin, Germany