Spin-dependent tunneling of single electrons into an empty quantum dot

Using real-time charge sensing and gate pulsing techniques we measure the ratio of the rates for tunneling into the excited and ground spin states of a single-electron quantum dot at an AlGaAs/GaAs interface in a magnetic field parallel to the interface. We find that the ratio decreases with increasing magnetic field until tunneling into the excited spin state is completely suppressed. However, we find that by adjusting the voltages on the surface gates to change the orbital configuration of the dot, we can restore tunneling into the excited spin state and that the ratio reaches a maximum when the dot is symmetric.