1. Department of Physics, Indian Institute of Technology Hyderabad, Kandi, Medak, 502 285Telangana, India
2. Department of Physics, Applied Physics and Astronomy, Binghamton University, State University of New York, P.O. Box 6000, Binghamton, 13902-6000New York, United States
3. School of Physics, University of Hyderabad, Prof. C. R. Rao Road, Gachibowli, Hyderabad, 500046Telangana, India