Department of Physics, The George Washington University, Washington, DC 20052, USA.|Department of Physics, The George Washington University, Washington, DC 20052, USA.|Department of Physics, The George Washington University, Washington, DC 20052, USA.|Department of Physics, The George Washington University, Washington, DC 20052, USA.|Department of Physics, The George Washington University, Washington, DC 20052, USA.|Department of Physics, The George Washington University, Washington, DC 20052, USA.