1. Department of Physics, West Chester University, West Chester, Pennsylvania 19383, USA
2. Department of Physics, Lehigh University, Bethlehem, Pennsylvania 18015, USA
3. Division of Materials and Manufacturing Science, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan
4. Van der Waals-Zeeman Institute, University of Amsterdam, Science Park 904, 1098 XH Amsterdam, The Netherlands