1. Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA
2. Geballe Laboratory for Advanced Materials, Departments of Applied Physics, Stanford University, Stanford, California 94305, USA
3. Departments of Physics, Stanford University, Stanford, California 94305, USA
4. Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
5. School of Physics and Astronomy, Tel-Aviv University, Tel-Aviv 69978, Israel