Lattice Dynamics and Specific Heat of $\alpha$ - GeTe: a theoretical and experimental study

TL;DR

This study combines theoretical ab initio calculations and experimental measurements to analyze the lattice dynamics and specific heat of rhombohedral GeTe, revealing the influence of hole concentration on its thermal properties.

Contribution

It provides a comprehensive analysis of GeTe's phonon density of states and specific heat, highlighting the effect of hole doping on thermal behavior, supported by both calculations and experiments.

Findings

Specific heat depends on hole concentration at low temperatures and near the maximum of C_p/T^3.

Ab initio calculations explain the increase in the maximum of C_p/T^3 with hole doping.

Experimental data confirms the theoretical predictions about hole concentration effects.

Abstract

We extend recent \textit{ab initio} calculations of the electronic band structure and the phonon dispersion relations of rhombohedral GeTe to calculations of the density of phonon states and the temperature dependent specific heat. The results are compared with measurements of the specific heat. It is discovered that the specific heat depends on hole concentration, not only in the very low temperature region (Sommerfeld term) but also at the maximum of $C_p/T^3$ (around 16 K). To explain this phenomenon, we have performed \textit{ab initio} lattice dynamical calculations for GeTe rendered metallic through the presence of a heavy hole concentration ($p$ $\sim$ 2$\times$ 10$^{21}$ cm$^{-3}$). They account for the increase observed in the maximum of $C_p/T^3$.