1. Catalan Institute
of Nanoscience and Nanotechnology (ICN2), CSIC and The Barcelona Institute of Science and Technology, Campus UAB, 08193 Barcelona, Spain
2. Institute of Structural Mechanics, Bauhaus-Universität Weimar, Marienstrasse
15, D-99423 Weimar, Germany
3. CINaM - Centre Interdisciplinaire de Nanoscience
de Marseille, Aix-Marseille Université, Campus Luminy,
Case 913, 13288 Marseille Cedex 9, France
4. Dipartimento
di Fisica, Universit di Cagliari, Cittadella Universitaria, I-09042 Monserrato, Cagliari, Italy
5. ICREA - Institució Catalana de Recerca i Estudis Avançats, 08010 Barcelona, Spain