1. CAS Key Laboratory of Nanophotonic Materials and Devices, CAS Key Laboratory of Standardization and Measurement for Nanotechnology, National Center for Nanoscience and Technology, Beijing 100190, P.R. China
2. University of Chinese Academy of Sciences, Beijing 100190, P.R. China
3. Organisch-Chemisches Institut, Universität Münster, Corrensstraße 40, 48149 Münster, Germany
4. Institute for Solid State Theory and Center for Multiscale Theory and Computation, Universität Münster, Wilhelm-Klemm-Straße 10, 48149 Münster, Germany
5. Physikalisches Institut, Universität Münster, Wilhelm-Klemm-Straße 10, 48149 Münster, Germany
6. Center for Nanotechnology, Heisenbergstraße 11, 48149 Münster, Germany