1. Department of Physics and Engineering Physics, Tulane University, New Orleans, Louisiana 70118, United States
2. Technological Institute for Superhard and Novel Carbon Materials, Moscow, 142190, Russian Federation
3. Moscow Institute of Physics and Technology, Dolgoprudny, 141700, Russian Federation
4. National University of Science and Technology “MISiS”, Moscow, 119049, Russian Federation
5. Department of Physics, University of Warwick, Coventry, CV4 7AL, United Kingdom