Magnetic field evolution of spin blockade in Ge/Si nanowire double quantum dots

We perform transport measurements on double quantum dots defined in Ge/Si core/shell nanowires and focus on Pauli spin blockade in the regime where tens of holes occupy each dot. We identify spin blockade through the magnetic field dependence of the leakage current. We find both a dip and a peak in the leakage current at zero field. We analyze this behavior in terms of quantum dot parameters such as coupling to the leads, interdot tunnel coupling, as well as spin-orbit interaction. We estimate a lower bound on the spin-orbit parameter corresponding to an upper bound of lso=500 nm for the Rashba spin-orbit length. We also extract effective Landé g factors up to 8.0 from field-dependent spin blockade measurements.