Ultraslow Spin Relaxation Dynamics in Colloidal Copper-Doped CdSe Quantum Dots

Bulk semiconductors doped with copper ions have been heavily studied and employed as phosphors in early display technologies. The properties of copper-doped semiconductor nanostructures are much less studied. In particular, the spin properties of photoexcited carriers in copper-doped colloidal quantum dots are virtually unknown. Understanding the spin processes in these materials can lead to applications in novel information technologies. Moreover, the spin structure of the excited states in Cu-doped dots is analogous to that of Cu(I) molecular complexes, which are widely studied with respect to applications in organic light emitting diodes. Thus, understanding the spin properties of Cu-doped dots can have broad ramifications for other material systems. In this work, we study the dynamics of spin relaxation processes in photoexcited Cu-doped CdSe colloidal quantum dots at helium temperatures and in magnetic fields up to 8 T. We find that a spin polarization is induced by application of the magnetic field....