1Department of Physics, Faculty of Engineering, Kyushu Institute of Technology, Kitakyushu, Japan
2Institut für Theoretische Physik II, Ruhr-Universität Bochum, Bochum, Germany
3M. Smoluchowski Institute of Physics, Jagiellonian University, Kraków, Poland
4Department of Physics and Astronomy, The University of Iowa, Iowa City, USA