Discrete breathers of new type in monoatomic chains

TL;DR

This paper introduces a new type of stable discrete breathers in strained monoatomic chains with Lennard-Jones interactions, characterized by smooth decay and arithmetic progression amplitudes, differing from traditional staggered modes.

Contribution

The study reveals a novel static non-homogeneous structure and associated discrete breathers with unique properties, expanding understanding of nonlinear localized modes in monoatomic chains.

Findings

Discovered a stable static non-homogeneous structure in strained chains.

Identified new discrete breathers with smooth decay and arithmetic progression amplitudes.

Demonstrated stability of these breathers up to 20-30% amplitude of interparticle distance.

Abstract

In strained monoatomic chains with Lennard-Jones interactions, we revealed a stable static non-homogeneous structure appearing as a result of a certain phase transition. Positions of individual particles in this structure form an exact arithmetic progression whose difference depends on the value of the strain. For N-particle chain, this structure is characterized by one long and N-1 short interatomic distances (bonds). In the vicinity of the static structure, we found discrete breathers of new type which essentially differ from the traditional breathers in the form of Sievers-Takeno and Page modes. It is well known that these modes possess some staggered structures and demonstrate exponential decay of the particle amplitudes from the core to their tails. In contrast to such properties, our breathers are characterised by smooth decay and amplitudes of the particles form approximately a decreasing arithmetic progression. Core of these breathers is located on two particles with long bond in static structure. Our breathers demonstrate soft type of nonlinearity (the frequency decreases with increasing of amplitudes) and they are stable dynamical objects for amplitudes up to 20%-30% of interparticle distance of the strained equidistant chain. For infinitely small amplitudes these breathers tend to the above described static non-homogeneous structure. We studied dependence of their properties on amplitude, strain and the number of particles in the chain. There exist a reason to suppose that the above static and dynamical structures can exist in real monoatomic chains consisting of carbon, boron, and other atoms.