Depolarization shift in quasi-one-dimensional quantum-well wires

The collective antisymmetric intersubband resonances of a quasi-one-dimensional quantum-well wire are analyzed in detail in the case of many occupied subbands. It is shown that for a lateral parabolic electron confinement potential the collective resonances form bands with a small depolarization shift. Split from these bands, separate collective resonances exist, showing a large depolarization shift. The various resonances should be observable in far-infrared optical-spectroscopy experiments. If the lateral confinement potential consists of an initial ideal parabolic potential, which is screened by the electrons in the well, it is shown analytically by first-order perturbation theory that the depolarization shift vanishes.