Breakdown of effective phonon theory in one-dimensional chains with asymmetric interactions

TL;DR

This paper investigates the limitations of effective phonon theory in one-dimensional chains with asymmetric interactions, showing that asymmetry causes significant deviations from theoretical predictions due to stronger phonon-phonon interactions.

Contribution

The study demonstrates the breakdown of effective phonon theory in asymmetric chains, highlighting the impact of interaction symmetry on phonon behavior.

Findings

Simulation matches theory for symmetric interactions

Significant deviations occur in asymmetric interactions

Asymmetry enhances phonon-phonon interactions

Abstract

Phonons are universal language for solid state theory. Effective phonon theory (self-consistent harmonic approximation) have been extensively used to access the weakly nonlinear effect in solid materials, which are standard content in textbook. In this manuscript, we test the effective phonon theory in one-dimensional chains with asymmetric interactions. It is found that simulation results agree well with theoretical predictions for symmetric cases, while significantly deviate from theoretical predictions for asymmetric cases. Our results imply the asymmetric interaction can provide stronger phonon-phonon interaction, which lead to break down of the effective phonon theory.