Weak violation of spin blockade in many-electron ground state resonances of a quantum dot

We present measurements on spin blockade in a laterally integrated quantum dot. The dot is tuned into the regime of strong Coulomb blockade, confining $\sim 50$ electrons. At certain spin states we find an additional mechanism suppressing electron transport, which we identify as spin blockade at zero bias (type-II). We verify this by probing the bias, magnetic field and temperature dependence. Weak violation of this blockade is modelled by detailed calculations of non-linear transport taking into account forbidden spin transitions.