Addition energies and density dipole response of quantum rings under the influence of in-plane electric fields

Within density functional theory, we address the effect of an in-plane electric field [script E] on the ground state and the density dipole response of a many-electron quantum ring, which is also submitted to a perpendicular magnetic field B. Addition energies and density dipole spectra are discussed as a function of [script E]. For the two-electron case, an exact numerical calculation is performed, obtaining the spin-phase diagram in the [script E]-B plane and showing that transitions between singlet and triplet spin states can be induced by varying the fields. We also find that, in spite of the deformation that [script E] causes in the electronic density, the spin of the ground state of a given electron number ring is very robust, changing little as the strength of the electric field is reasonably increased.