Supersonic motion of high frequency vibrational soliton in monatomic chain

TL;DR

This paper investigates the supersonic and subsonic movement of vibrational solitons in monatomic chains with anharmonicities, highlighting the role of cubic and quartic anharmonicities in stabilizing these localized vibrations.

Contribution

It introduces the concept of supersonic vibrational solitons stabilized by cubic anharmonicity in monatomic chains, expanding understanding of nonlinear lattice dynamics.

Findings

Subsonic solitons occur with weak cubic anharmonicity and hard quartic anharmonicity.

Supersonic solitons are stabilized by cubic anharmonicity-induced lattice deformation.

Quartic anharmonicity can be absent or soft in the supersonic case.

Abstract

Moving self-localized vibration of large size (vibrational soliton) in monatomic chain with cubic and quartic anharmonicities is considered. Two types of motion of such vibrations are found: the subsonic and the supersonic ones. First type of motion is possible for chains with hard quartic anharmonicity supposing that cubic anharmonicity is weak. This motion was earlier observed in numerical simulations. For the second type of motion the cubic anharmonicity plays the decisive role: the moving mode is stabilized by co-moving deformation of the lattice caused by this anharmonicity. The quartic anharmonicity in this case may be absent or even soft.