Phonon self-energy and origin of anomalous neutron scattering spectra in SnTe and PbTe thermoelectrics.
The anharmonic lattice dynamics of rock-salt thermoelectric compounds SnTe and PbTe are investigated with inelastic neutron scattering (INS) and first-principles calculations. The experiments show that, surprisingly, although SnTe is closer to the ferroelectric instability, phonon spectra in PbTe exhibit a more anharmonic character. This behavior is reproduced in first-principles calculations of the temperature-dependent phonon self-energy. Our simulations reveal how the nesting of phonon dispersions induces prominent features in the self-energy, which account for the measured INS spectra and their temperature dependence. We establish that the phase space for three-phonon scattering processes, combined with the proximity to the lattice instability, is the mechanism determining the complex spectrum of the transverse-optic ferroelectric mode.
Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
C W
CW
Li
Department of Physics, Chemistry and Biology, Linköping University, Linköping SE-581 83, Sweden.
O
O
Hellman
Quantum Condensed Matter Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
J
J
Ma
Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
A F
AF
May
Quantum Condensed Matter Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
H B
HB
Cao
Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
X
X
Chen
Quantum Condensed Matter Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
A D
AD
Christianson
Quantum Condensed Matter Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
G
G
Ehlers
Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
D J
DJ
Singh
Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
B C
BC
Sales
Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
O
O
Delaire
D007854:Lead / Q000737:chemistry*; D008956:Models, Chemical; D033363:Neutron Diffraction / Q000379:methods*; D060739:Phonons; D012666:Semiconductors; D013691:Tellurium / Q000737:chemistry*; D013816:Thermodynamics; D017971:Tin Compounds / Q000737:chemistry*
D017971:Tin Compounds; D007854:Lead; D013691:Tellurium