The Nuclear Dark State under Dynamical Nuclear Polarization

We analyze aspects of nuclear dark states.The formation of the dark states prevents the further establishment of nuclear polarizations,while inhomogeneous nuclear spin precessions can result in leakage from these states.An optimal efficiency for pumping nuclear polarization is achieved when the dynamical nuclear polarization(DNP)cycling rate is comparable to the dark-state leakage rate.When the DNP rate is much larger,the nuclear spin bath can be locked on the dark states.We propose schemes where the inhomogeneous precessions can be suppressed for the realization of large-scale dark states.As the dark states correspond to low transverse nuclear field fluctuations,they can be used to suppress the decoherence of the electron induced by the nuclear spins.