1. CNR-IOM Laboratorio Nazionale TASC, Basovizza
SS-14, km 163.5, 34149 Trieste, Italy
2. Faculty of Mathematics and Physics, University of Ljubljana, Jadranska 19, 1000 Ljubljana, Slovenia
3. Institute of Physics, Czech Academy of Sciences, Cukrovarnická 10, Prague 16200, Czech Republic
4. Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton, New York 11973, United States
5. Department of Physics, University of Trieste, via A. Valerio 2, 34127 Trieste, Italy
6. J. Stefan Institute, Jamova 39, SI-1000 Ljubljana, Slovenia