LAUSR

1 Department of Physics, Università degli Studi di Trieste, 34127 Trieste, Italy 2 Elettra Sincrotrone Trieste S.C.p.A., 34127 Basovizza Trieste, Italy 3 Joseph Henry Laboratories of Physics, Princeton University, Princeton, New Jersey 08544, USA Quantum Matter Institute, University of British Columbia, Vancouver, BC V6T 1Z4, Canada Department of Physics & Astronomy, University of British Columbia, Vancouver, BC V6T 1Z1, Canada 6 Centre Énergie Matériaux Télécommunications, Institut National de la Recherche Scientifique, Varennes, Québec J3X 1S2, Canada 7 Nanoelectronics Research Institute, National Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaraki 305-8568, Japan 8School of Physics and Astronomy, University of Minnesota, Minneapolis, Minnesota 55455, USA 9 Dipartimento di Fisica “E.R. Caianiello,” Universita` degli Studi di Salerno, I-84084 Fisciano (SA), Italy 10 CNR-SPIN, UOS di Salerno, I-84084 Fisciano (SA), Italy