Electronic structure of superconducting gallium-doped germanium from ab-initio calculations

TL;DR

This paper uses ab-initio calculations to analyze the electronic structure of gallium-doped germanium, a superconductor with a low critical temperature, revealing no impurity band and identifying a new phonon mode.

Contribution

It provides the first detailed ab-initio study of gallium-doped germanium's electronic and vibrational properties related to its superconductivity.

Findings

No impurity band observed in electronic structure.

Fermi level resides in the valence band of germanium.

A new phonon mode appears around 175 cm-1.

Abstract

Using ab-initio calculations, we study the electronic structure of gallium-doped germanium, which was found recently to be a superconductor, with a critical temperature of 0.5 Kelvins, and a particularly low density of Cooper pairs. The calculations of the electronic properties reveal that no sign of an impurity band is observed, and that the Fermi level lies in the valence band of Germanium. Moreover, the calculation of the phonon frequencies shows that a new mode associated to the Ga atom is appearing, around 175$ cm-1.