Fig. 4. Plasmon spectral function with amplitude given in color scale for an intrinsic monolayer of TaS₂ computed from first principles.

We consider only decay processes solely from phonon-assisted scatterings, since the plasmon is outside of the Landau damping regions for the plotted range of wavevectors. The plasmon linewidth Γ becomes slightly sharper for modes with higher frequencies due to the smaller density of final states that the plasmon can decay to (see Methods section). The intrinsic plasmon linewidth decreases from 1 meV at ~0.15 ${\AA }^{\mathrm{-1}}$ down to 0.3 meV at q ~ 0.3 ${\AA }^{\mathrm{-1}}$.