1. Department of Physics, Indian Institute of Science, Bangalore 560012, India
2. Theoretical Sciences Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Bangalore 560064, India
3. Institute of Physics, Bhubaneshwar 751005, India
4. Department of Physics, Ch. Charan Singh University, Meerut 250004, India
5. Center for Nano Science and Engineering, Indian Institute of Science, Bangalore 560012, India