Discrete gap breathers in a two-dimensional diatomic face-centered square lattice

In this paper we study the existence and stability of two-dimensional discrete gapbreathers in a two-dimensional diatomic face-centered square latticeconsisting of alternating light and heavy atoms, with on-sitepotential and coupling potential. This study is focused ontwo-dimensional breathers with their frequency in the gap thatseparates the acoustic and optical bands of the phonon spectrum. Wedemonstrate the possibility of the existence of two-dimensional gapbreathers by using a numerical method. Six types of two-dimensionalgap breathers are obtained, i.e., symmetric, mirror-symmetric andasymmetric, whether the center of the breather is on a light or aheavy atom. The difference between one-dimensional discrete gapbreathers and two-dimensional discrete gap breathers is alsodiscussed. We use Aubry's theory to analyze the stability ofdiscrete gap breathers in the two-dimensional diatomic face-centeredsquare lattice.