Fermi surface and electron dispersion of PbTe doped with resonant Tl impurity from KKR-CPA calculations

Abstract

We present results of a detailed study on the electron dispersions and Fermi surface of lead telluride doped with 2% of thallium, which is a resonant impurity in PbTe. Using the Korringa-Kohn-Rostoker method with the coherent potential approximation (KKR-CPA), Bloch spectral functions (BSFs), which replace the dispersion relations in alloys, are calculated, and BSF intensity maps over the Brillouin zone (alloy Fermi surface cross sections) are presented. It is shown that, close to the valence band edge, Tl does not create an isolated impurity band, but due to its resonant character, strongly disturbs the host electronic bands, leading to the disappearance of sharp and well-defined electronic energy bands. The consequences of this effect on the transport properties are discussed and a qualitative explanation for the improvement in the thermoelectric properties of PbTe:Tl is suggested.