Singlet-triplet spin blockade and charge sensing in a few-electron double quantum dot

Singlet-triplet spin blockade in a few-electron lateral double quantum dot is investigated using simultaneous transport and charge-sensing measurements. Transport from the 1,1 to the 0,2 electron occupancy states is strongly suppressed relative to the opposite bias 0,2 – 1,1 . At large bias, spin blockade ceases as the 0,2 triplet state enters the transport window, giving a direct measure of exchange splitting of the 0,2 state as a function of magnetic field. A simple model for current and steady-state charge distribution in spin-blockade conditions is developed and found to be in excellent agreement with experiment. Three other transitions 1,1 – 2,0 , 1,3 – 2,2 , and 1,3 – 0,4 exhibit spin blockade while other nearby transitions and opposite bias configurations do not, consistent with simple even-odd shell filling.