Optical and acoustic plasmons in cylindrical quantum-well wires

We study theoretically the collective electronic excitations of quasi-one-dimensional cylindrical quantum-well wires, the intrasubband and intersubband plasmons in the random-phase approximation. Using a two-subband model we calculate the dispersion curves for the case that two subbands are occupied. We study the influence of the image forces on the intrasubband and intersubband plasmons in detail. These modes are split in two branches. The intrasubband plasmon branches can be classified in an optical and an acoustic branch which are influenced quite differently by the image forces. The intersubband plasmon branches behave like acoustic plasmons.