Large systems of discrete breathers in graphene

Abstract

Nonlinear localized vibrational modes or discrete breathers are of great interest nowadays, because their role in different physical properties is still remaining unknown. Elastic strain engineering allows making quite a wide gap in the density of the phonon states of graphene, although undeformed graphene has no such a gap. Gap discrete breathers in graphene can possibly trigger defect or even crack and fracture formation and the investigation of its properties is of great importance nowadays. Clusters of discrete breathers in graphene can contribute to the considerable energy accumulation and, moreover, the energy exchange between discrete breathers was previously found. At the present work, systems composed of dozens of gap discrete breathers in graphene are investigated by molecular dynamics simulation at zero temperature. Different variations of the initial amplitudes of discrete breathers in the cluster and the combination of two initial phases are considered. It is shown that such clusters can survive for a long time during thousands oscillation periods. “Negative” initial displacement when atoms in the breather are moving towards each other is found to be more preferable in comparison with the “positive” initial displacement when atoms in the breather are moving from each other and allows excitation of the long-living breathers.