Pohl Institute of Solid State Physics Tongji University Shanghai 200092;
Institute fur ExperimentalphysikⅢ AG Festkorperspektroskopiej Ruhr-UniversiBochum 44780 Bochum F.R.G. P.O.Box 102148;
Institute fur ExperimentalphysikⅢ AG Festkorperspektroskopiej Ruhr-UniversiBochum 44780 Bochum F.R.G. P.O.Box 102148;
Institute fur ExperimentalphysikⅢ AG Festkorperspektroskopiej Ruhr-UniversiBochum 44780 Bochum F.R.G. P.O.Box 102148;
Pohl Institute of Solid State Physics Tongji University Shanghai 200092;
Institute fur ExperimentalphysikⅢ AG Festkorperspektroskopiej Ruhr-UniversiBochum 44780 Bochum F.R.G. P.O.Box 102148International Center for Materials Physics Academia Sinica Shenyang 110015;