Pauli spin blockade in carbon nanotube double quantum dots
  We report Pauli spin blockade in an impurity defined carbon nanotube double quantum dot. We observe a pronounced current suppression for negative source-drain bias voltages which is investigated for both symmetric and asymmetric coupling of the quantum dots to the leads. The measured differential conductance agrees well with a theoretical model of a double quantum dot system in the spin-blockade regime which allows us to estimate the occupation probabilities of the relevant singlet and triplet states. This work shows that effective spin-to-charge conversion in nanotube quantum dots is feasible and opens the possibility of single-spin readout in a material that is not limited by hyperfine interaction with nuclear spins. 
M.R. Buitelaar, J. Fransson, A.L. Cantone, C.G. Smith, D. Anderson,   G.A.C. Jones, A. Ardavan, A.N. Khlobystov, A.A.R. Watt...