Effect of off-center positively charged Coulomb impurity on Dirac states in graphene magnetic dot

Using numerical diagonalization, we study the effect of the position of an off-center positively charged Coulomb impurity in a graphene magnetic dot, whose magnetic field profile is chosen as a Gaussian type. Numerical results show that the electron-hole symmetry is broken by the Coulomb potential and the originally zero energy states become nondegenerate and split into hole-like states. For the higher Landau levels shown, owing to the competition between the repulsive Coulomb potential and the magnetic confinement, the level orderings are reversed in the hole states at critical magnetic fields. Similar results are also obtained in the dot-size dependence of the low-lying spectra. © 2014 Elsevier Ltd.