Plasmonics in graphene at infrared frequencies

We point out that plasmons in doped graphene simultaneously enable low losses and significant wave localization for frequencies below that of the optical phonon branch $\ensuremath{\hbar}{\ensuremath{\omega}}_{Oph}\ensuremath{\approx}0.2\text{ }\text{eV}$. Large plasmon losses occur in the interband regime (via excitation of electron-hole pairs), which can be pushed toward higher frequencies for higher-doping values. For sufficiently large dopings, there is a bandwidth of frequencies from ${\ensuremath{\omega}}_{Oph}$ up to the interband threshold, where a plasmon decay channel via emission of an optical phonon together with an electron-hole pair is nonegligible. The calculation of losses is performed within…