Stark shift in single and vertically coupled type-I and type-II quantum dots

We theoretically studied the Stark effect on an exciton in single and vertically coupled type-I and type-II quantum dots. Only for the single type-I dot does the exciton energy show a parabolic dependence on the applied field. A dipole moment is induced by the applied electric field for vertically coupled type-I dots and for type-II dots, leading to a linear dependence of the Stark shift on the electric field. Furthermore, we predict that spontaneous symmetry breaking can occur for vertically coupled type-II dots leading to a permanent dipole moment.