1. Department of Molecular Science and Technology Ajou University Suwon 443‐749 Korea
2. Department of Physics Korea Advanced Institute of Science and Technology (KAIST) Daejeon 34141 Korea
3. Institute of Applied Physics University of Bern Bern 3012 Switzerland
4. Institute of Computational Physics Zurich University of Applied Sciences (ZHAW) Winterthur 8401 Switzerland