Acoustic impedance and interface phonon scattering in Bi$_2$Te$_3$ and other semiconducting materials

TL;DR

This paper uses first principles calculations to analyze phonon dispersions and interface scattering in Bi2Te3, revealing anisotropic acoustic velocities and the importance of the local density approximation for accurate modeling.

Contribution

It introduces a model for interface scattering considering acoustic wave anisotropy and compares phonon behaviors across different semiconducting materials.

Findings

Local density approximation better describes phonon dispersions in Bi2Te3.

Strong anisotropy observed in acoustic phonon velocities.

Developed a model for interface scattering in ceramics considering anisotropy.

Abstract

We present first principles calculations of the phonon dispersions of Bi2Te3 and discuss these in relation to the acoustic phonon interface scattering in ceramics. The phonon dispersions show agreement with what is known from neutron scattering for the optic modes. We find a difference between the generalized gradient approximation and local density results for the acoustic branches. This is a consequence of an artificial compression of the van der Waals bonded gaps in the Bi2Te3 structure when using the generalized gradient approximation. As a result local density approximation calculations provide a better description of the phonon dispersions in Bi$_{2}$Te$_{3}$. A key characteristic of the acoustic dispersions is the existence of a strong anisotropy in the velocities. We develop a model for interface scattering in ceramics with acoustic wave anisotropy and apply this to Bi2Te3 and compare with PbTe and diamond.