Two-laser dynamic nuclear polarization with semiconductor electrons: Feedback, suppressed fluctuations, and bistability near two-photon resonance

摘要

We present how optical coherent population trapping (CPT) of the spin oflocalized semiconductor electrons stabilizes the surrounding nuclear spin bathvia the hyperfine interaction, resulting in a state which is more ordered thanthe thermal equilibrium state. We find distinct control regimes for differentsigns of laser detuning and examine the transition from an unpolarized,narrowed state to a polarized state possessing a bistability. The narrowing ofthe state yields slower electron spin dephasing and self-improving CPT. Ouranalysis is relevant for a variety of solid state systems wherehyperfine-induced dephasing is a limitation for using electron spin coherence.