Pauli spin blockade in weakly coupled double quantum dots

In a two-level system, constituted by two serially coupled single level quantum dots, coupled to external leads we find that the current is suppressed in one direction of biasing caused by a fully occupied two-electron triplet state in the interacting region. The efficiency of the current suppression is governed by the ratio between the interdot tunnelling rate and the level offset. In the opposite bias direction, the occupation of the two-electron triplet is lifted which allows a larger current to flow through the system, where the conductance is provided by transitions between one-electron states and two-electron singlet states. It is also shown that a finite ferromagnetic interdot exchange interaction provides an extended range of the current suppression, while an antiferromagnetic exchange leads to a decreased range of the blockade regime.