1. Department of Physics, University of Birjand, Birjand 97175-615, Iran
2. Department of Physics, Institute for Advanced Studies in Basic Sciences, Zanjan 45195-1159, Iran
3. Department of Physics, Shahid Bahonar University, Kerman 76169-73439, Iran
4. Department of Chemical Engineering and Materials Science, University of Southern California, Los Angeles, California 90089-1211, United States