Plasmons in quantum wires

An interesting way to investigate the properties of porous Si is to look at its plasmons. The reason of it lies on the collective nature of the plasmon excitations, much more sensitive to the dimensions of the medium than the single particle excitations. It is indeed well known that in a free-electron system the plasmon frequency varies from Ωp(infinite solid) to Ωp/√2(planar surface), to Ωp/√3(spherical dot).The comparison between the experimental study of the plasmon on porous silicon and the results of theoretical studies can provide many useful information on the structural and optical properties of this unusual material. An overview of the plasmon features in a (semiconductor) quantum wire is presented. A peculiarity of this system relies on the strong anisotropy of the medium, therefore the full tensorial nature of the dielectric response should be considered.