1. Frontier Research Institute for Interdisciplinary Sciences, Tohoku University, Sendai 980-8578, Japan
2. Department of Physics, Tohoku University, Sendai 980-8578, Japan
3. Department of Electrical and Computer Engineering, Rice University, Houston, Texas 77005, United States
4. School of Mechanical Engineering, Hanoi University of Science and Technology, Hanoi 100000, Viet Nam
5. Department of Chemistry, Zhejiang University, Hangzhou, Zhejiang 310058, China
6. Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
7. Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States