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

摘要

We present results of detailed study on the electron dispersions and Fermisurface of lead telluride doped with $2\%$ of thallium, which is resonantimpurity in PbTe. Using the KKR--CPA method, Bloch spectral functions (BSFs),which replace the dispersion relations in alloys, are calculated, and BSFsintensity maps over the Brillouin zone (alloy Fermi surface cross-sections) arepresented. It is shown, that close to the valence band edge, Tl does not createan isolated impurity band, but due to its resonant character, strongly disturbsthe host electronic bands, leading to disappearance of sharp and well definedelectronic energy bands. Consequences of this effect on the transportproperties are discussed and new qualitative explanation of the improvement inthermoelectric properties of PbTe:Tl is suggested.