Success and breakdown of the T-matrix approximation for phonon-disorder scattering

TL;DR

This paper assesses the accuracy of the T-matrix approximation for phonon-disorder scattering, revealing its limitations for low-energy flexure phonons in 2D materials and explaining its success in highly disordered systems.

Contribution

It introduces an unfolding algorithm for large-scale simulations and analyzes the conditions under which the T-matrix approximation is valid or breaks down.

Findings

T-matrix approximation fails for low-energy flexure phonons in 2D materials.

The approximation is effective in describing maximally disordered mass systems.

An unfolding formalism is developed for large-scale phonon simulations.

Abstract

We examine the validity of the widely used T-matrix approximation for treating phonon-disorder scattering by implementing an unfolding algorithm that allows simulation of disorder up to tens of millions of atoms. The T-matrix approximation breaks down for low-energy flexure phonons that play an important role in thermal transport in two-dimensional materials. Furthermore, insights are developed into the success of the T-matrix approximation in describing maximally mass disordered systems. To achieve this, the phonon unfolding formalism is generalized to describe mass disorder and strongly nonperturbative features of the spectrum are connected to the Boltzmann quasiparticle picture.