Crossover between different universality classes: Scaling for thermal transport in one dimension

TL;DR

This study uses direct dynamics simulations to explore how different phonon dispersions and parameters cause crossover between universality classes in 1D thermal transport, revealing tunable scaling behaviors.

Contribution

It demonstrates the existence of a crossover between universality classes in 1D thermal transport and links this to phonon dynamics modeled as continuous-time random walks.

Findings

Crossover between different universality classes observed.

Scaling exponents can be tuned by anharmonicity and temperature.

Phonon transport resembles Levy walks influenced by dispersion and nonlinearity.

Abstract

For thermal transport in one-dimensional (1D) systems, recent studies have suggested that employing different theoretical models and different numerical simulations under different system's parameter regimes might lead to different universality classes of the scaling exponents. In order to well understand the universality class(es), here we perform a direct dynamics simulation for two archetype 1D oscillator systems with quite different phonon dispersions under various system's parameters and find that there is a crossover between the different universality classes. We show that by varying anharmonicity and temperatures, the space-time scaling exponents for the systems with different dispersions can be feasibly tuned in different ways. The underlying picture is suggested to be understood by phonons performing various kinds of continuous-time random walks (in most cases, be the L\'{e}vy walks but not always), probably induced by the peculiar phonon dispersions along with nonlinearity. The results and suggested mechanisms may provide insights into controlling the transport of heat in some 1D materials.