1. Condensed Matter Theory Group, Department of Physics and AstronomyUppsala University Uppsala 75120 Sweden
2. Laboratoire de Physique des Matériaux et Modélisations des SystèmesMoulay Ismail UniversityFaculty of Sciences, Department of Physics (LP2MS), Unité Associée au CNRST‐URAC 08 Meknes B.P. 11201 Morocco
3. Department of Microtechnology and Nanoscience (MC2)Chalmers University of Technology Gothenburg SE‐412 96 Sweden
4. Max‐Planck‐Institut für Physik Complexer Systeme NöthnitzerStr. 38 Dresden D‐01187 Germany
5. Applied Materials Physics, Department of Materials and EngineeringRoyal Institute of Technology (KTH) Stockholm S‐100 44 Sweden
6. Department of Materials Science and NanoEngineeringRice University 6100 Main Street Houston Texas 77005 USA