Inelastic light scattering by electronic excitations in artificial atoms

Abstract

In the paper, we present theoretical calculations of the cross section for inelastic light scattering by electronic excitations in a quantum dot charged with 42 electrons. The many-electron states involved in the computations are obtained in the framework of the Random Phase Approximation. The evaluation of energy-weighted sum rules allowed us to distinguish among single-particle (SPEs), collective charge (CDEs) and collective spin (SDEs) electronic excitations. Raman spectra in polarized and depolarized geometries are computed for a range of incident laser energies. The below-band-gap excitation regime reveals advantages for the identification of individual excited states contributing to the Raman spectra. The computed polarization ratios for Raman intensities show the breakdown of selection rules in the presence of a magnetic field. A new jump rule of Raman intensities at the band gap may help identifying the nature (charge or spin) of electronic excitations. Under extreme resonance (laser energy very close to the band gap), Raman spectra are dominated by SPEs. For incident laser energies 40 -- 50 meV above band gap, a correct desciption of Raman spectra is shown to require the proper account of energy widths of intermediate states.