Nanosecond spin coherence of excitons bound to acceptors in a CdTe quantum well.

We have studied the coherent spin dynamics of excitons bound to acceptors, A⁰X, immersed in a CdTe quantum well by using time resolved photo-induced Faraday rotation. We have also measured the time-resolved differential transmission in order to determine a A⁰X lifetime of 220 ps, which is independent of the applied magnetic field. We show that at low magnetic field, the spin of A⁰X is completely frozen during a time, ≅ 4.5 ns, at least twenty times longer than its lifetime. We compare the spin properties of A⁰X with the spin properties of other charged excitons systems, and we conclude that the hyperfine interaction of the photo-created electron spin with nuclear spins is very likely to be at the origin of the observed spin dephasing times. [ABSTRACT FROM AUTHOR]