Phonons scattering off discrete asymmetric solitons in the absence of a Peierls-Nabarro potential

TL;DR

This study investigates how phonon wave-packets scatter off asymmetric kink solitons in a discrete $$ model without Peierls-Nabarro potential, revealing frequency-dependent transmission, reflection, and kink velocity changes.

Contribution

It introduces a method to analyze phonon-kink interactions in a discrete $$ model without Peierls-Nabarro potential, highlighting frequency-dependent scattering and kink motion.

Findings

Large lattice spacing leads to complete phonon reflection.

Smaller lattice spacing results in frequency-dependent transmission and reflection.

Kinks can acquire velocity from wave-packet interactions.

Abstract

We analyze the interaction of lattice vibrations (phonon wave-packets) with an asymmetric kink soliton initially at rest. We employ the $\phi^6$ model in one space and one time dimensions for various lattice spacings and consider two different discretization prescriptions for the field potential that do not generate Peierls-Nabarro potentials, i.e. the kink can be placed anywhere along the lattice beyond discrete translational invariance. Since the $\phi^6$ model kink is neither symmetric nor anti-symmetric under spatial reflections we simulate the cases where the wave-packet approaches the kink from negative or positive spatial infinity. We extract the energy transmission and reflection coefficients as functions of the central frequency of the phonon wave-packet for the different lattice spacings. For large lattice spacings the wave-packet is always fully reflected while for smaller spacing the amount of reflection and transmission depends on the central frequency. We also identify scenarios in which the target kink acquires a non-zero velocity from its interaction with the wave-packet.