[1] Univ So Calif, Dept Mat Sci & Elect Engn, Los Angeles, CA 90089 USA
[2] Univ Texas Austin, Texas Mat Inst, Dept Mech Engn, Austin, TX 78712 USA
[3] Univ Texas Austin, Texas Mat Inst, Ctr Nano & Mol Sci & Technol, Austin, TX 78712 USA
[4] Univ Maryland, Dept Phys, College Pk, MD 20742 USA
[5] Univ Maryland, Ctr Supercond Res, College Pk, MD 20742 USA
[6] Univ Maryland, Dept Mat Sci & Engn, College Pk, MD 20742 USA