Intrinsically undamped plasmon modes in narrow electron bands

Surface plasmons in 2-dimensional electron systems with narrow Bloch bands feature an interesting regime in which Landau damping (dissipation via electron-hole pair excitation) is completely quenched. This surprising behavior is made possible by strong coupling in narrow-band systems characterized by large values of the "fine structure" constant \alpha=e^2/\hbar \kappa v_{\rm F} Dissipation quenching occurs when dispersing plasmon modes rise...