FUNDAMENTAL STEPS OF THE GROUP-VELOCITY FOR SLOW SURFACE-POLARITONS IN THE 2-DIMENSIONAL ELECTRON-GAS IN A HIGH MAGNETIC-FIELD

A new type of collective electromagnetic excitation, namely surface po laritons (SP) - in a 2D electronic layer in a high magnetic field, is predicted. We have found the spectrum, damping, and polarization of th e SP over a wide range of frequencies omega and wavevectors k. it is s hown that near the cyclotron resonance (CR) (omega similar to Omega = eB/mc) the phase velocity of the SP is drastically slowed down and the group velocity is quantized into fundamental steps defined by the fin e-structure constant cr = e(2)/hc. In the vicinity of a CR subharmonic (omega similar to 2 Omega), negative (anomalous) dispersion of the SP occurs. The relaxation of electrons in the 2D layer gives rise to a n ew dissipative collective threshold-type mode of the SP. We suggest a method for calculating the kinetic coefficients for the 2D electronic layer in a high magnetic field, using the Wigner distribution function formalism, and determine their spatial and frequency dispersions. Usi ng this method we have calculated the lineshapes of the CR, which are in goad agreement with experimental data.