Graphene quantum dot with a hydrogenic impurity

We investigate the electronic energy levels of a circular graphene quantum dot with a hydrogenic impurity placed at the center of the dot. We have adopted a variational scheme in such a way that the trial wave functions take into account the carrier confinement due to the dot geometry as well as the effect of the magnetic field. We found that the presence of impurity strongly modifies the electronic spectrum of the graphene quantum dot. We also calculated the critical value of the impurity strength as a function of dot radius.