Theoretical investigation of collective excitation of a multiple-quantum-well system superlattice

Abstract

We consider a finite type-II superlattice with different dielectric media on either side of the surfaces, which consist of unit cells with alternating electron and hole layers in the unit cell. Under some assumptions, we have studied the density-density correlation function including overlap effects between electron and hole wave functions of adjacent layers using the random-phase approximation. We have obtained the dispersion relation for surface and bulk plasmons in a few cases. Furthermore, we have calculated the Raman intensity in order to compare the result with those of others.

Optical properties of a multiple quantum well in a HgTe/CdTe system

“…The model system of N unit cells, each of which contains two layers, HgTe and CdTe layers, has 2N and N quantum wells for the electron-like and the heavy-hole-like states, respectively, in the HgTe layers, and 2N quantum wells for the light-hole-like states in the CdTe layers. The particle states in the unit cell are assumed to be of the form (Kim and Sohn 1994)…”

“…where 0 nm , the polarizability of the non-interacting system, which is due to the polarizability between one zeroth subband which overlaps with the nth subband, and another zeroth subband which overlaps with the mth subband, is layer independent (Hawrylak et al 1986). V nm,rs (l, l ) is the Coulomb interaction between the layers in the unit cells, including the effect of image charges and subband structure (Grecu 1973, Hawrylak et al 1985a, b, Eliasson et al 1987, Kim and Sohn 1994:…”

“…We decompose V ij tw nm,n m (k z , k z ) and ij tw nm,n m (k z , k z ) obtained by the Fourier transform of V nm,nm (l, l ) and ij tw nm,n m (l, l ) into the bulk part and the surface part (Hawrylak et al 1985a, b, 1986, Eliasson et al 1987 and rewrite ij tw nm,n m (k z , k z ) as a matrix Π(k z , k z ). Then the equation gives two coupled equations of Π B (Kim and Sohn 1994) and Π S .…”

“…In section 2, the density-density correlation function is derived under the random-phase approximation for semi-infinite space (Kim and Sohn 1994) described above. Calculations are carried out analytically as far as possible.…”

“…We here include the intersubband scattering of incoming light with the electron-light state and the heavy-hole-like states in HgTe layers and the light-hole-like state in CdTe layers. In section 3, dispersion spectra (Kim and Sohn 1994) of the surface and bulk plasmon for infinite layers are calculated. Dispersion spectra of the bulk plasmons are also calculated as a function of the number of unit cells for various carriers.…”