1. Department of Materials Physics and Chemistry, University of Science and Technology Beijing, Beijing 100083, People's Republic of China
2. Department of Physics, Aberystwyth University, Aberystwyth SY23 3BZ, United Kingdom
3. Centre for the Physics of Materials and Department of Physics, McGill University, Montreal, Quebec H3A2T8, Canada
4. State Key Laboratory of Heavy Oil Processing, China University of Petroleum-Beijing, Beijing 102249, China