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

Abstract

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.

Propagation effect on photoluminescence of spin-aligned high-density exciton magnetic polarons in Cd 0.8 Mn 0.2 Te

“…The PL intensity increased with the excitation density to the power of 5.8. This change in the PL spectra and the superlinearity of the PL intensity were already reported as typical behavior of the HD-EMPs [14,16,17].…”

“…Therefore, it is possible to achieve spin-aligned HD-EMPs; these are attractive because they are expected to induce a large photo-induced magnetization. To date, in the case of the selective excitation of localized excitons, the PL band arising from HD-EMPs was reported in Cd 0.8 Mn 0.2 Te [14][15][16]. By applying an external magnetic field in a Faraday configuration, the spectral width of the PL band was broadened and the peak energy showed a redshift.…”

Photoinduced magnetization of magnetic polarons in Cd0.8Mn0.2Te under high‐density resonant excitation of free exciton

“…Photoexcitation of electron-hole pairs of a semimagnetic semiconductor results in an exciton and the exciton aligns spins of magnetic ions in its area of the wave function through the s, p-d exchange interaction; finally the exciton becomes an exciton magnetic polaron. In these days, we reported discovery of a nonlinear PL band of Cd 0.8 Mn 0.2 Te (hereinafter referred to as high-density exciton magnetic polaron band: HD-EMP band) by selective excitation of the localized exciton [1]. As the origin of the HD-EMP band, we suggested the high-spin state of HD-EMP.…”

Polarization memory effect on nonlinear photoluminescence of semimagnetic semiconductor Cd0.8Mn0.2Te

“…The X band shows nonlinear growth on excitation power and peculiar low energy shift with application of magnetic field. Therefore, as the origin of the X band, authors presented the high-spin state of the dense magnetic polarons: in this state, every spins of electrons (holes) point one direction and this spin alignment leads to enhanced magnetic polaron effect [7]. Furthermore, the X band shows characteristic oscillation structure with application of a weak magnetic field.…”

“…The polarization memory effect of the X band most likely originates from the sufficiently long phase relaxation time of the photo excited electrons and holes of the X band. The life time of the X band is about 60 ps [7] and the relaxation from excitation energy (1.927 eV in Fig. 2) to the PL energy (1.9134 eV in Fig.…”