Temperature effects on the electronic band structure of PbTe from first principles

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PhysRevMaterials.3.055405.pdf(802.73 KB)
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Querales-Flores, José D.
Cao, Jiang
Fahy, Stephen B.
Savić, Ivana
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We report a fully ab initio calculation of the temperature dependence of the electronic band structure of PbTe. We address two main features relevant for the thermoelectric figure of merit: the temperature variations of the direct gap and the difference in energies of the two topmost valence band maxima located at L and Σ. We account for the energy shift of the electronic states due to thermal expansion, as well as electron-phonon interaction computed using the nonadiabatic Allen-Heine-Cardona formalism within density functional perturbation theory and the local density approximation. We capture the increase of the direct gap with temperature in very good agreement with experiment. We also predict that the valence band maxima at L and Σ become aligned at ∼600–700K. We find that both thermal expansion and electron-phonon interaction have a considerable effect on these temperature variations. The Fan-Migdal and Debye-Waller terms are of almost equal magnitude but have an opposite sign, and the delicate balance of these terms gives the correct band shifts. The electron-phonon induced renormalization of the direct gap is produced mostly by high-frequency optical phonons, while acoustic phonons are also responsible for the alignment of the valence band maxima at L and Σ.
Electrical conductivity , Electron-phonon coupling , Electronic structure , First-principles calculations , Thermoelectric effects , Crystalline systems , Narrow band gap systems , Thermoelectric systems , Density functional theory
Querales-Flores, J. D., Cao, J., Fahy, S. and Savić, I. (2019) 'Temperature effects on the electronic band structure of PbTe from first principles', Physical Review Materials, 3(5), 055405. (11pp.) DOI: 10.1103/PhysRevMaterials.3.055405
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