1. Center for Nonlinear Studies, Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
2. Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
3. Center for Integrated Nanotechnologies, Center for Nonlinear Studies, and Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA