Sequential magnetotunneling in a vertical quantum dot tuned at the crossing to higher spin states

We have calculated the linear magnetoconductance across a vertical parabolic quantum dot with a magnetic field in the direction of the current. Gate voltage and magnetic field are tuned at the degeneracy point between the occupancies $N=2\mathrm{}$ and $N=3,$ close to the singlet-triplet transition for $N=2.\mathrm{}$ We find that the conductance is enhanced prior to the transition by nearby crossings of the levels of the three-particle dot. Immediately after it is depressed by roughly 1/3, as long as the total spin S of the three-electron ground state doesn’t change from $S=1/2\mathrm{}$ to $S=3/2,$ due to spin selection rule. At low temperature this dip is very sharp, but the peak is recovered by increasing the temperature.