Dominant electron-phonon scattering mechanisms in $n$-type PbTe from first principles

• Main Authors: Cao, Jiang, Querales-Flores, Jose D, Murphy, Aoife R, Fahy, Stephen, Savić, Ivana
• Format: Journal Article
• Language: English
• Published: 11-09-2018
• Subjects: Physics - Mesoscale and Nanoscale Physics
• DOI: 10.48550/arxiv.1809.03799

Phys. Rev. B 98, 205202 (2018) We present an \emph{ab-initio} study that identifies the main electron-phonon
scattering channels in $n$-type PbTe. We develop an electronic transport model
based on the Boltzmann transport equation within the transport relaxation time
approximation, fully parametrized from first-principles calculations that
accurately describe the dispersion of the electronic bands near the band gap.
Our computed electronic mobility as a function of temperature and carrier
concentration is in good agreement with experiments. We show that longitudinal
optical phonon scattering dominates electronic transport in $n$-type PbTe,
while acoustic phonon scattering is relatively weak. We find that scattering
due to soft transverse optical phonons is by far the weakest scattering
mechanism, due to the symmetry-forbidden scattering between the conduction band
minima and the zone center soft modes. Soft phonons thus play the key role in
the high thermoelectric figure of merit of $n$-type PbTe: they do not degrade
its electronic transport properties although they strongly suppress the lattice
thermal conductivity. Our results suggest that materials like PbTe with soft
modes that are weakly coupled with the electronic states relevant for transport
may be promising candidates for efficient thermoelectric materials.