Spin blockade and nuclear spin effect in a g-factor modulated vertical double quantum dot

We report on-going research on a low temperature transport properties of a g  -factor modulated vertical double quantum dot device. The double dot consists of GaAs dot and In0.04Ga0.96AsIn0.04Ga0.96As dot, and electron g-factors of two dots are largely different from each other. We observed a step like change of a leakage current in spin-blockade region as a function of magnetic field or source–drain voltage, and found that the position of current step in magnetic field decreases with increasing the source–drain voltage. We attribute the current step comes from nuclear-spin-assisted electron spin scatterings. At this magnetic field the two-electron spin singlet and triplet state energy crossover. Our model consisting of two-electron and two-site Hubbard Hamiltonian with different g-factor on each site gives good agreement between the observed magnetic field and source–drain voltage relation and the calculated one.