Eur. Phys. J. B 29, 279-283 (2002)
https://doi.org/10.1140/epjb/e2002-00301-0

Standing wave instabilities, breather formation and thermalization in a Hamiltonian anharmonic lattice

¹ Department of Physics and Measurement Technology, Linköping University, 581 83 Linköping, Sweden
² Laboratoire Léon Brillouin (CEA-CNRS), CEA Saclay, 91191 Gif-sur-Yvette Cedex, France
³ Department of Physics, University of Crete, PO Box 2208, 71003, Heraklion, Crete, Greece

Corresponding author: ^a mjn@ifm.liu.se

Received: 6 October 2001
Revised: 1 March 2002
Published online: 2 October 2002

Abstract

Modulational instability of travelling plane waves is often considered as the first step in the formation of intrinsically localized modes (discrete breathers) in anharmonic lattices. Here, we consider an alternative mechanism for breather formation, originating in oscillatory instabilities of spatially periodic or quasiperiodic nonlinear standing waves (SWs). These SWs are constructed for Klein-Gordon or Discrete Nonlinear Schrödinger lattices as exact time periodic and time reversible multibreather solutions from the limit of uncoupled oscillators, and merge into harmonic SWs in the small-amplitude limit. Approaching the linear limit, all SWs with nontrivial wave vectors () become unstable through oscillatory instabilities, persisting for arbitrarily small amplitudes in infinite lattices. The dynamics resulting from these instabilities is found to be qualitatively different for wave vectors smaller than or larger than , respectively. In one regime persisting breathers are found, while in the other regime the system thermalizes.