Spin-dependent tunneling into an empty lateral quantum dot

Motivated by the recent experiments of Amasha et al. [Phys. Rev. B 78, 041306 (R) (2008)], we investigate single electron tunneling into an empty quantum dot in presence of a magnetic field. We numerically calculate the tunneling rate from a laterally confined, few-channel external lead into the lowest orbital state of a spin-orbit coupled quantum dot. We find two mechanisms leading to a spin-dependent tunneling rate. The first originates from different electronic g factors in the lead and in the dot, and favors the tunneling into the spin ground (excited) state when the g factor magnitude is larger (smaller) in the lead. The second is triggered by spin-orbit interactions via the opening of off-diagonal spin-tunneling channels. It systematically favors the spin-excited state. For physical parameters corresponding to lateral GaAs/AlGaAs heterostructures and the experimentally reported tunneling rates, both mechanisms lead to a discrepancy of similar to 10% in the spin-up vs spin-down tunneling rates. We conjecture that the significantly larger discrepancy observed experimentally originates from the enhancement of the g factor in laterally confined lead.