Abstract

We demonstrate how coherent population trapping (CPT) of donor-bound electron spins in GaAs results in autonomous feedback producing stabilized states for the spin polarization of nuclei around the electrons. The feedback mechanism arises from the interplay between CPT and dynamic nuclear spin polarization (DNP). CPT was realized by two-laser excitation of a bound-exciton state, see Fig. 1a,e. In order to probe the feedback response, we use transmission studies of the spectral CPT feature on an ensemble of electrons which directly reveals the underlying statistical distribution of the prepared nuclear spin states. Fig. 1 shows how tuning the laser driving from blue (∆> 0) to red detuned (∆< 0) drives a transition from one to two stable states. Laser detuning drives a transition from an unpolarized, narrowed state to a polarized state possessing a bistability. After the control scheme is applied, the narrowing of the state protects the electron spin against dephasing for over 20 minutes (via the Knight field) and yields self-improving CPT.

© 2015 IEEE