Supersonic motion of high frequency vibrational soliton in monatomic chain

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.