Skutterudite antimonides: Quasilinear bands and unusual transport

Abstract

Electronic-structure calculations are reported for ${\mathrm{IrSb}}_{3}$, ${\mathrm{CoSb}}_{3}$, and ${\mathrm{CoAs}}_{3}$ in the skutterudite structure. The band structures show a pseudogap around the Fermi level. The single band, which crosses the pseudogap, touches the conduction-band minimum at the \ensuremath{\Gamma} point in ${\mathrm{CoAs}}_{3}$ and ${\mathrm{IrSb}}_{3}$ and almost touches it in ${\mathrm{CoSb}}_{3}$ due to a different ordering of the conduction bands. The dispersion of this gap-crossing band is quadratic at the \ensuremath{\Gamma} point as expected, but for the antimonides it remarkably crosses over to linear behavior extremely close to the band edge, so that for doping levels as low as 3\ifmmode\times\else\texttimes\fi{}${10}^{16}$ holes/${\mathrm{cm}}^{3}$ the properties are determined by the linear dispersion. This yields interesting transport effects, such as a completely off-diagonal inverse mass tensor and unusual doping dependencies of the hole mobility and Seebeck coefficient. The Seebeck coefficients calculated from the band dispersion are in excellent agreement with experiment.

Keywords

Affiliated Institutions

• United States Naval Research Laboratory US

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