1. KTH Royal Institute of Technology, AlbaNova University Center, SE-10691 Stockholm, Sweden
2. Department of Physics, Presidency University, 86/1 College Street, Kolkata 700073, India
3. Department of Physics and Astronomy, Uppsala University, Box 516, SE-75120 Uppsala, Sweden
4. S.N. Bose National Centre for Basic Sciences, JD-III, Salt Lake, Kolkata 700098, India