Theory of the linewidth of intersubband plasmons in quantum wells.

Intersubband (ISB) plasmons in remotely doped wide quantum wells acquire a linewidth even at zero temperature and in-plane wave vector q(parallel) = 0 by a combination of intrinsic (electron-electron interaction) and extrinsic effects (impurities and interface roughness). We present a quantitatively accurate theory of the linewidth that treats both effects on equal footing and from first principles by a combination of time-dependent density-functional theory with the memory function formalism. Comparison with recent optical absorption experiments shows that the ISB plasmon linewidth has a significant contribution from electron-electron interaction, and is only weakly related to the mobility.