1. Department of Physics, Brooklyn College and the Graduate Center of the City University of New York, Brooklyn, New York 11210, USA
2. Ioffe Institute, 26 Polyteckhnicheskaya, St. Petersburg 194021, Russia and Peter the Great St. Petersburg Polytechnic University, St. Petersburg, Russia
3. Ioffe Institute, 26 Polyteckhnicheskaya, St. Petersburg 194021, Russia
4. Department of Applied Physics, New York University-Tandon School of Engineering, Brooklyn, New York 11201, USA