Spin correlations in spin blockade

We investigate spin currents and spin-current correlations for double quantum dots in the spin blockade regime. By analysing the time evolution of the density matrix, we obtain the spin resolved currents and derive from a generating function an expression for the fluctuations and correlations. Both the charge current and the spin current turn out to be generally super-Poissonian. Moreover, we study the influence of ac fields acting upon the transported electrons. In particular, we focus on fields that cause spin rotation or photon-assisted tunnelling.