We show for the first time that highly localized in-plane breathers can propagate in specific directions with minimal lateral spreading in a model 2-D hexagonal non-linear lattice. The lattice is subject to an on-site potential in addition to longitudinal nonlinear inter-particle interactions. This study investigates the prediction that stable breather-like solitons could be formed as a result of energetic scattering events in a given layered crystal and would propagate in atomic-chain directions in certain atomic planes. This prediction arose from a long-term study of previously unexplained dark lines in natural crystals of muscovite mica.63.20.Pw, 63.20.Ry, 03.40.Kf.The response of a nonlinear 2D atomic lattice when embedded in a surrounding 3D lattice is presently of much interest in connection with transport phenomena in layered crystals. Two examples of such crystals are the copper-oxide based high temperature superconductors and the potassium based silicate muscovite mica. Fortunately the optical transparency of the latter allows the study of energetic events at the atomic level. This is possible in mica because of tracks made visible by impurities of transient defects, through triggered solid-state phase transitions. A study of these tracks arising from nuclear scattering events led to the suggestion that energy could be transported over large distances through the crystal by some sort of energetic intrinsic localized mode (ILM) on the lattice [1]. The interesting and novel aspect of this prediction was that these ILMs would travel along the crystal axes and remain localized in both longitudinal and transverse directions with little or no lateral spreading. This is despite the fact that the 2D lattice has full hexagonal symmetry. This one-dimensional behavior in a two-dimensional lattice was called quasi-onedimensional (QOD) and the resulting ILMs were called "quodons" [2].The purpose of this present letter is to demonstrate numerical simulations of a mica-like model which support the QOD conjecture. Our intention is not to provide a detailed model of the mica system at this stage, but merely to present a simplified model which maintains much of the overall qualitative features of the mica system and yet can be easily studied. The model is general enough to suggest the possibility of QOD effects in other hexagonal crystal structures, and even other geometries such as square lattices.Muscovite mica has a layered structure. A conspicuous feature of this structure is the mono-atomic planes of *

We report the ejection of atoms at a crystal surface caused by energetic breathers which have travelled more than 10 7 unit cells in atomic chain directions. The breathers were created by bombardment of a crystal face with heavy ions. This effect was observed at 300K in the layered crystal muscovite, which has linear chains of atoms for which the surrounding lattice has C2 symmetry. The experimental techniques described could be used to study breathers in other materials and configurations.

No abstract

All high-Tc superconductors have a layered structure, but the importance of this remains unclear. Some of these layers have chains of atoms with a local symmetry, which facilitates quasi-one-dimensional effects. We describe numerical simulations which suggest that lattice nonlinearities allow the transport of strongly localized and robust packets of vibrational energy (discrete breathers) along these chains. The results support previous studies which correlated these particular structural properties with superconductivity in these cuprates.