1. Department of Physics and Texas Center for Superconductivity, University of Houston, Houston, Texas 77204-5002, USA
2. Department of Chemistry and Texas Center for Superconductivity, University of Houston, Houston, Texas 77204-5003, USA
3. Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
4. Department of Physics, Boston College, Chestnut Hill, Massachusetts 02467, USA
5. Lawrence Berkeley National Laboratory, Berkeley California 94720, USA