1. Department of Applied Physics, School of Science, Xi’an Jiaotong University, Xi’an 710049, China
2. Moscow Institute of Physics and Technology, Dolgoprudny, Moscow Region 141700, Russia
3. Institute of Spectroscopy, Russian Academy of Sciences, Troitsk, Moscow 108840, Russia
4. Department of Physics, University of Bath, BA2 7AY Bath, United Kingdom