New types of one-dimensional discrete breathers in a two-dimensional lattice

Discrete breather (DB) is a spatially localized and periodic in time, large-amplitude vibrational mode in a nonlinear lattice. According to some experimental and a number of molecular dynamics studies, crystal lattices support various types of DBs. The final goal in the study of DBs is to understand their impact on macroscopic crystal properties. This aim cannot be achieved without further data collection on the properties of all types of DBs supported by the crystals. Recently k-dimensional DBs in n-dimensional crystal lattices (k < n) have been introduced. Such DBs are delocalized in k dimensions and localized in n - k dimensions. In the present study 2D triangular lattice with the classical Lennard-Jones potential is considered (n = 2) and new types of one-dimensional DBs (k = 1) are presented. The DBs are localized in one close-packed atomic row and the vibration amplitudes of the atoms decrease exponentially with the distance from this row. Quite general approach for excitation of such DBs is used, which is based on the delocalized nonlinear vibrational modes (DNVMs) derived by Chechin with co-authors for a nonlinear chain. We find that DNVMs reported by them produce one-component and two-component, one-dimensional DBs with relatively long lifetime in the triangular lattice. Our results contribute to the theory of nonlinear lattice dynamics and eventually will help to understand the role of DBs in crystalline solids.