Oscillation modes of two-dimensional nanostructures within the time-dependent local-spin-density approximation

We apply the time-dependent local-spin-density approximation as general theory to describe ground states and spin-density oscillations in the linear response regime of two-dimensional nanostructures of arbitrary shape. For this purpose, a frequency analysis of the simulated real-time evolution is performed. The effect on the response of the recently proposed spin-density waves in the ground state of certain parabolic quantum dots is considered. They lead to the prediction of a new class of excitations, soft spin-twist modes, with energies well below that of the spin dipole oscillation. PACS 73.20.Dx, 72.15.Rn Typeset using REVTEX