Spin-related transport in ultra small Si quantum dots

We investigated electron transport through ultra small Si quantum dots. We found that the $B$-dependence of energy levels is dominated by the Zeeman shift, allowing us to measure the spin difference between two successive ground states directly. In some dots the number of electrons N in the dot can be tuned starting from zero, and the total spin of the dot can be mapped as a function of N and B. For one of the dots we deduced that the dot becomes spontaneously polarized at N=6 with a large spin change \Delta S=3/2, demonstrating the essential features of spin blockade. Surprisingly, for N>20, the transitions with \Delta S>1/2 do not lead to the suppression of the corresponding peaks at low temperatures.