Finite temperature dynamical polarization and plasmons in gapped graphene

Abstract

In this study we report our numerical results on finite temperature non-interacting dynamical polarization function, plasmon modes and electron energy loss function of doped single layer gapped graphene within the random phase approximation. We find that the interplay of linear energy band dispersion, chirality, bandgap and temperature endow single layer gapped graphene with strange polarizability behaviour which is a mixture of 2DEG, single layer and bilayer graphene and as a result the plasmon spectrum also manifests strikingly peculiar behaviour. The plasmon dispersion is observed to be suppressed till temperatures up to ~0.5Tf, similar to the gapless graphene case but beyond 0.5Tf a reversal in trend is seen in gapped graphene, for all values of band gap. This behaviour is also corroborated by the density plots of electron energy loss function. The opening of a small gap also generates a new undamped plasmon mode which is found to disappear at high temperatures. The plasmonic behaviour of gapped graphene is further found to be hugely influenced by the substrate on which the gapped graphene sheet rests, which signifies the need for a careful substrate selection in the making of desirable graphene based plasmonics devices.