1. Department of Physics and Astronomy and Nebraska Center for Materials and Nanoscience, University of Nebraska-Lincoln, Lincoln, Nebraska 68588, USA
2. Racah Institute of Physics, Hebrew University of Jerusalem, Jerusalem 91904, Israel
3. Department of Physics and Astronomy, George Mason University, Fairfax, Virginia 22030, USA
4. Quantum Science and Engineering Center, George Mason University, Fairfax, Virginia 22030, USA