ABSTRACT The subject of the present paper is a thorough numerical investigation of plasmon expectations, their dispersions and damping within a Lieb lattice. The Lieb lattice is known for its unique low‐energy band structure which consists of a bandgap as well as a flat band intersecting the conduction band at its lowest point. In contrast to previously studied dice lattice, the location of the current flat band exhibits reduced and broken symmetries, which give rise to interesting electronic and optical properties of this new material. In this work, we have investigated the conditions for observing a well‐defined and stable plasmon mode within a wide frequency range. Specifically, we have considered a free‐standing layer with various doping levels, as well as different types of monolayers of the Lieb lattice interacting with a surface‐plasmon mode localized on top of a semi‐infinite conductor. In particular, we have observed and described fully long‐living plasmon modes with unusual energy dispersions. Additionally, we have carried out a detailed investigation on the static screening associated with the Lieb lattice. Our study has further revealed that these predicted features seem to be quite different from those of pseudospin‐1 materials but resemble those of graphene instead.
Iurov et al. (Sun,) studied this question.