Coupling of 2D plasmons to nonlocal bulk plasmons

An explicit closed-form position-space expression for the highly inhomogeneous inverse dielectric response function of a quantum well (QW) of finite width (with a single bound subband state) embedded in a bulk medium having a continuum of extended states is derived here analytically. The resulting position-dependent nonlocal dynamic inverse dielectric function epsilon (-1)(z,z';q(\ \),omega), given in position representation for the z-direction across the well, depends on the in-plane wave vector q(\ \) and frequency w as well as on the positional variables z, z'. Spatial inhomogeneity arises from the lack of translational invariance in the z-direction due to the presence of the QW. The frequency poles of epsilon (-1)(z, z'; q(\ \),omega) obtained here represent the coupling of nonlocal bulk plasmons with two-dimensional (2D) intrasubband plasmons of the QW. The dispersion relation of the coupled modes is examined. The bulk particle-hole modes damp the collective excitations of the coupled 2D and bulk systems and we estimate the damping rate. (C) 2001 Elsevier Science B.V. All rights reserved.