Undamped relativistic magnetoplasmons in lossy two-dimensional electron   systems
  We address electrodynamic effects in plasma oscillations of a lossy 2D electron system whose dc 2D conductivity is comparable to the speed of light. We argue that the perpendicular constant magnetic field B causes astonishing features of magnetoplasma dynamics. We show that plasmon-polariton spectra can be classified using a 'relativistic' phase diagram 2D conductivity divided by the speed of light versus B. An extraordinarily low damping branch in magnetoplasmon-polariton spectra emerges at two phases of this diagram. Some magnetoplasmons at these phases are predicted to be undamped waves. 
V.A. Volkov, A.A. Zabolotnykh
cond-mat.mes-hall physics.plasm-ph