Electron-phonon scattering and thermoelectric transport in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>p</mml:mi></mml:math>-type PbTe from first principles
Ransell D’Souza, Jiang Cao, José D. Querales-Flores, Stephen Fahy, Ivana Savić
Abstract
We present a first-principles-based model of electron-phonon scattering mechanisms and thermoelectric transport at the $L$ and $\mathrm{\ensuremath{\Sigma}}$ valleys in $p$-type PbTe, accounting for their thermally induced shifts. Our calculated values of all thermoelectric transport parameters at room temperature are in very good agreement with experiments for a wide range of doping concentrations. Scattering due to longitudinal optical phonons is the main scattering mechanism in $p$-type PbTe, while scattering due to transverse optical modes is the weakest. The $L$ valleys contribute most to thermoelectric transport at 300 K due to the sizable energy difference between the $L$ and $\mathrm{\ensuremath{\Sigma}}$ valleys. We show that both scattering between the $L$ and $\mathrm{\ensuremath{\Sigma}}$ valleys and additional transport channels of the $\mathrm{\ensuremath{\Sigma}}$ valleys are beneficial for the overall thermoelectric performance of $p$-type PbTe at 300 K. Our findings thus support the idea that materials with high valley degeneracy may be good thermoelectrics.