1. State Key Laboratory of Electronic
Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu, Sichuan 610054,
P. R. China
2. Center for Integrated Nanotechnologies, Los Alamos National Laboratory, Los Alamos, New Mexico
87545, United States
3. Department of
Physics and Astronomy, University of Texas at San Antonio, San Antonio, Texas
78249, United States
4. Department
of Physics and the
Texas Center for Superconductivity, University of Houston, Houston, Texas 77204, United States