High-density selective excitation effect on excitons in semimagnetic semiconductor CdMnTe

Many body effects among electron-hole pairs and exchange interaction of spins between electron/hole and Mn 2+ ions have been investigated in a semimagnetic semiconductor of CdMnTe under the selective excitation of high-density localized excitons with use of a picosecond pulse laser. A new nonlinear luminescence band (X band) has been found on the high-energy side of conventional exciton magnetic polaron band and its peak energy shows a pronounced red shift with the increase of excitation power and/or with the application of magnetic field. Time-resolved luminescence without magnetic field has revealed the characteristic behaviour of the X band with a longer rise time for the higher energy side. However, this tendency disappears with the application of magnetic field. As the origin of the X band, we propose the high-density spin-polarized electron-hole pairs interacting with microscopic Mn 2+ -ion spins aligned through the exchange interaction.