Underlying mechanisms for normal heat transport in one-dimensional anharmonic oscillator systems with a double-well interparticle interaction

TL;DR

This study investigates the mechanisms behind the transition from superdiffusive to normal heat transport in one-dimensional anharmonic oscillator systems with double-well interactions, revealing complex energy and momentum spreading behaviors.

Contribution

It provides a detailed simulation-based analysis of heat, energy, and momentum spreading, clarifying the conditions for normal heat conduction and the decoupling of energy and heat diffusion.

Findings

Verified crossover from superdiffusive to normal heat transport.

Energy spreading is distinct from heat diffusion, with localization effects.

Unusual non-ballistic momentum transport occurs at specific temperatures.

Abstract

Previous studies have suggested a crossover from superdiffusive to normal heat transport in one-dimensional (1D) anharmonic oscillator systems with a double-well type interatomic interaction like $V(\xi)=-\xi^2/2+\xi^4/4$, when the system temperature is varied. In order to better understand this unusual manner of thermal transport, here we perform a direct dynamics simulation to examine how the spreading processes of the three physical quantities, i.e., the heat, the total energy and the momentum, would depend on temperature. We find three main points that are worth noting: (i) The crossover from superdiffusive to normal heat transport is well verified from a new perspective of heat spread; (ii) The spreading of the total energy is found to be very distinct from heat diffusion, especially that under some temperature regimes, energy is strongly localized, while heat can be superdiffusive. So one should take care to derive a general connection between the heat conduction and energy diffusion; (iii) In a narrow range of temperatures, the spreading of momentum implies clear unusual non-ballistic behaviors; however, such unusual transport of momentum cannot be directly related to the normal transport of heat. An analysis of phonons spectra suggests that one should also take the effects of phonons softening into account. All of these results may provide insights into establishing the connection between the macroscopic heat transport and the underlying dynamics in 1D systems.