Spin-polarized multiexcitons in quantum dots in the presence of spin-orbit interaction

An efficient electron spin-relaxation mechanism has been observed in InAs quantum dots (QDs) that manifests itself as a sharp drop in the circular polarization of the light emitted by Fe spin-light emitting diodes, which incorporate a single layer of InGaAs QDs, for a narrow range of magnetic fields around 5 T. The underlying mechanism occurs when the QDs are occupied by three-electron-hole pairs forming a tri-exciton (3X) and is a two-step process. The first step involves the spin flip of one of the three electrons mediated by the spin-orbit interaction; in the second step the 3X relaxes to its ground state via phonon emission.