Collective interband excitations in the Raman spectra of quantum wires

A unifying theory for the collective interband excitations of the interacting electrons in a quantum wire with several occupied subbands is developed by using the bosonization method. Interband spin- and charge-density excitations for two subbands are treated in detail. The results are used to clarify the physical nature of the interband modes detected in recent Raman scattering experiments, especially the so-called single-particle excitations.