Pauli-spin blockade in a vertical double quantum dot holding two to five electrons

We use a vertical double quantum dot (QD) to study spin blockade (SB) for the twoto five-electron states. SB observed for the twoand four-electron states is both assigned to Pauli exclusion with formation of a spin triplet state, and lifted by singlet-triplet admixing due to fluctuating nuclear field. SB observed for the five-electron state is caused by combined Pauli effect and Hund’s rule. We observe a hysteretic behavior of the SB leakage current for up and down sweep of magnetic field, and argue that SB and its lifting by hyperfine interaction are subtle with the spin configuration and modified depending on the inter-dot detuning and number of electrons.