1. Institute for Physics of Microstructures, Russian Academy of Sciences, 603807 Nizhny, Novgorod, Russian Federation
2. Department of Physics, University of Konstanz, 78457 Konstanz, Germany
3. Institute of Physics for Advanced Materials, Nanotechnology and Photonics (IFIMUP)/Departamento de Física e Astronomia, Universidade do Porto, 4169-007 Porto, Portugal
4. Department of Materials Science and Engineering, University of Virginia, 395 McCormik Road, Charlottesville, Virginia 22904-4745, United States