1. Department of Physics, Indian Institute of Technology Patna, Bihta Campus, Bihta, Bihar 801106, India
2. Indiana University-Purdue University Indianapolis, Indianapolis, Indiana 46202, United States
3. School of Optical and Electronic Information, Huazhong University of Science and Technology, Luoyu Road 1037, Wuhan 430074, China
4. University at Buffalo−SUNY, 3435 Main Street, Buffalo, New York 14214, United States
5. Theoretical Sciences Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Bangalore 560064, India
6. University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
7. University of Illinois at Urbana−Champaign, 1304 West Springfield Ave, Urbana, Illinois 61801, United States