1. Center for Integrated Nanotechnologies (CINT) Los Alamos National Laboratory Los Alamos NM 87545 USA
2. Nebraska Center for Energy Sciences Research University of Nebraska‐Lincoln Lincoln NE 68583 USA
3. Department of Materials Design and Innovation University at Buffalo–The State University of New York Buffalo NY 14260 USA
4. Division of Quantum Phases and Devices Department of Physics Konkuk University Seoul 143‐701 South Korea