Optical response of two-dimensional few-electron concentric double   quantum rings: A local-spin-density-functional theory study
  We have investigated the dipole charge- and spin-density response of few-electron two-dimensional concentric nanorings as a function of the intensity of a perpendicularly applied magnetic field. We show that the dipole response displays signatures associated with the localization of electron states in the inner and outer ring favored by the perpendicularly applied magnetic field. Electron localization produces a more fragmented spectrum due to the appearance of additional edge excitations in the inner and outer ring. 
Francesc Malet, Mart\'i Pi, Manuel Barranco, Enrico Lipparini, and   Lloren\c{c} Serra