Spin Blockades in Linear and Nonlinear Transport through Quantum Dots

The transport properties of a quantum dot that is weakly coupled to leads are investigated by using the exact quantum states of a finite number of interacting electrons. It is shown that, in addition to the Coulomb blockade, spin selection rules strongly influence the low temperature transport and lead to experimentally observable effects. Transition probabilities between states that correspond to successive electron numbers vanish if the total spins differ by $\left|\Delta S\right|>\mathrm{}\frac{1}{2}$. In nonlinear transport, this can lead to negative differential conductances. The linear conductance peaks are suppressed if transitions between successive ground states are forbidden.