1. Institute of Physics, Bijenička 46, HR-10000 Zagreb, Croatia
2. Istituto Officina dei Materiali (IOM)-CNR Laboratorio TASC, I-34149 Trieste, Italy
3. International Centre for Theoretical Physics (ICTP), I-34100 Trieste, Italy
4. Department of Engineering Physics, Electronics and Mechanics, Graduate School of Engineering, Nagoya Institute of Technology, Nagoya 466-8555, Japan
5. University of Zagreb, Faculty of Science, Department of Chemistry, HR-10000 Zagreb, Croatia