COLLECTIVE ELECTROMAGNETIC EXCITATIONS IN A DOUBLE-LAYER 2-DIMENSIONAL ELECTRON-SYSTEM IN A HIGH MAGNETIC-FIELD

A new type of collective electromagnetic excitations, namely the surfa ce polaritons (SP's), in a double-layer two-dimensional electron syste m (DL2DES) (of nn-type, pp-type, and np-type) in a high magnetic field is predicted. Using a Wigner distribution function formalism, we inve stigate the spectrum, damping, and polarization of the SP's in a wide range of the frequencies omega and the wave vectors k. It is shown tha t near the cyclotron resonance (CR) (omega similar to Omega=eB/mc) the phase velocity of the SP's is drastically slowed down, and the group velocity undergoes the fundamental steps defined by the fine-structure constant alpha=e(2)/(h) over bar c (as well as for the one-layer 2DES ). For the nn-type DL2DES, each dispersion curve splits, and strongly correlated collective electromagnetic excitations propagate in the sys tem. The group velocity of these excitations is defined by the interla yer distance d, and is much smaller than that for the one-layer 2DES. In the vicinity of a CR subharmonic (omega similar to 2 Omega) the neg ative (anomalous) dispersion of the SP occurs. For the np-type DL2DES the branches of the dispersion curves are intercrossed in the long-wav e region, near the subharmonic (hole) CR, and in the short-wave region , due to the resonance interaction between the principal (electron) CR mode and the subharmonic (hole) CR made. The relaxation of the electr ons (or holes) in the DL2DES leads to the occurrence of a dissipative collective mode of the SP type-the ''additional SP's'' (ASP's). This m ode exists under certain threshold condition, which is determined by a fine-structure constant alpha. As a consequence, the dispersion curve s for these excitations exhibit spectrum endpoints, and mode's conflue nce. The threshold condition for the ASP's in the DL2DES has a ''geome trical oscillating'' form due to the coherence effects between the spl it ASP modes, The potential Importance for various applications in mic roelectronics is discussed.