This article is cited in 7 papers

Lattice dynamics

Gap discrete breathers in a two-component two-dimensional crystal in thermal equilibrium

S. V. Dmitriev, L. Z. Khadeeva

Institute for Metals Superplasticity Problems of RAS, Ufa

Abstract: Crystals having a gap in the phonon spectrum can maintain gap discrete breathers (DBs), i.e., nonlinear localized oscillatory modes existing in the absence of defects and having a frequency lying in the gap. The lifetime of gap DBs in a two-dimensional perfect crystal of the composition $A_3B$ in thermal equilibrium has been studied by the molecular dynamics method. As was shown earlier, the existence of gap DBs in such a crystal is provided by the presence of a wide gap in the phonon spectrum if the component mass ratio $m_A/m_B$ is sufficiently large. For comparison, a crystal with a relatively small ratio $m_A/m_B$ is considered when the gap in the spectrum is absent and the existence of gap DBs is impossible in the case of a weak nonlinearity realized in the considered case. It has been shown that, in contrast to the opposite case, in a crystal maintaining gap DBs, long-lived localized oscillatory modes of large amplitude can emerge, whose concentration and lifetime increase with temperature.

Received: 18.10.2010

 English version: Physics of the Solid State, 2011, 53:7, 1425–1430

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