Spin charging sequences in three colinear laterally coupled vertical quantum dots

The electronic properties of three colinear and laterally coupled vertical quantum dots are investigated by three-dimensional self-consistent simulations based on the density functional theory within the local spin density approximation. From a simulation viewpoint, it is shown that the physical dimensions of experimentally realizable mesa structures should be optimized to produce equal size quantum dots. Single electron charging sequences are studied as a function of two sets of gate voltage configurations, i.e., center gate variation on the center dot mesa and side gate variation on the two outer dot mesas, separately. In the former, electrons are shown to relocalize from the outer dots to the center dot with the onset of a spin-density wavelike profile for three and four electrons, respectively. In the latter, double charging is seen to take place with the onset of localization in each of the outer dots for N=3 and N=4 electrons. Finally, we obtain the stability diagram of the system, showing features specific to the colinear triple quantum dots (TQD) coupling.