[1] Department of Physics, University of California, Santa Barbara,CA,93106-9530, United States
[2] Materials Department, University of California, Santa Barbara,CA,93106-5050, United States
[3] Department of Physics and Astronomy, Rutgers University, Piscataway,NJ,08845-0849, United States
[4] Center for Physical Sciences and Technology, Vilnius,LT-10257, Lithuania