Broadband focusing of acoustic plasmons in graphene with an applied current

Nonreciprocal plasmons in current-driven, isotropic, and homogenous graphene with proximal metallic gates are theoretically explored. Nearby metallic gates screen the Coulomb interactions, leading to linearly dispersive acoustic plasmons residing close to its particle-hole continuum counterpart. We show that the applied bias leads to spectral broadband focused plasmons whose resonance linewidth is dependent on the angular direction relative to the current flow due to Landau damping. We predict that forward focused nonreciprocal plasmons are possible with accessible experimental parameters and setup.