1. Research School of Physics, The Australian National University, Canberra, ACT 2601, Australia
2. Center for Nanoscale Systems, Harvard University, Cambridge, Massachusetts 02138, USA
3. Dipartimento di Fisica e Astronomia “Galileo Galilei,” Universià di Padova, 35131 Padova, PD, Italy
4. U.S. Army Combat Capabilities Development Command—Armament Center, Watervliet, New York 12189, USA