1. Research Center for Exotic Nanocarbons (JST), Shinshu University, 4-17-1 Wakasato, Nagano-city 380-8553, Japan
2. Instituto de Física, Universidade Federal da Bahia, Salvador, Bahia 40.210-340, Brazil
3. Physics and Astronomy Department, Michigan State University, East Lansing, Michigan 48824, United States
4. Faculty of Engineering, Shinshu University, 4-17-1 Wakasato, Nagano-city 380-8553, Japan