Spin and density longitudinal response of quantum dots in the time-dependent local-spin-density approximation

The longitudinal dipole response of a quantum dot has been calculated in th e far-infrared regime using local-spin-density-functional theory. We have s tudied the coupling between the collective spin and density modes as a func tion of the magnetic field. We have found that the spin dipole mode and sin gle-particle excitations have a sizable overlap, and that the magnetoplasmo n modes can be excited by the dipole spin operator if the dot is spin polar ized. The frequency of the dipole spin edge mode presents an oscillation wh ich is clearly filling factor (v) related. We have found that the spin dipo le mode is especially soft for even-v values. Results for selected numbers of electrons and confining potentials are discussed. [S0163-1829(99)02223-7 ].