Anomalous transverse optic phonons in SnTe and PbTe -- revisited

Broken mirror symmetry tuned topological transport in PbTe/SnTe heterostructures

The tunability of topological surface states and controllable opening of the Dirac gap are of great importance to the application of topological materials. In topological crystalline insulators (TCIs), crystal symmetry and topology of electronic bands intertwine to create topological surface states and thus the Dirac gap can be modulated by symmetry breaking structural changes of lattice. By transport measurement on heterostructures composed of p-type topological crystalline insulator SnTe and n-type conventional semiconductor PbTe, here we show a giant linear magnetoresistance (up to 2150% un…

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 …

Anharmonic phonon spectra of PbTe and SnTe in the self-consistent harmonic approximation

At room temperature, PbTe and SnTe are efficient thermoelectrics with a cubic structure. At low temperature, SnTe undergoes a ferroelectric transition with a critical temperature strongly dependent on the hole concentration, while PbTe is an incipient ferroelectric. By using the stochastic self-consistent harmonic approximation, we investigate the anharmonic phonon spectra and the occurrence of a ferroelectric transition in both systems. We find that vibrational spectra strongly depends on the approximation used for the exchange-correlation kernel in density functional theory. If gradient corr…

Establishing phase diagram for the band engineering in p-type PbTe/SnTe from elementary electronic structure understanding

Band engineering is an important mechanism to increase the thermopower of thermoelectric materials by reconstructing the band structure near Fermi level. PbTe and SnTe are the most representative systems in which band engineering were achieved by various dopants. Starting with the elementary understanding of the band structures, we established the phase diagram for the band engineering in p-type PbTe/SnTe by constructing an s-p bonding model. We show that the effects of band tuning are mainly determined by an inherent parameter of doping element: the s orbital energy level. With the phase diag…

Impurity clustering and impurity-induced bands in PbTe-, SnTe-, and GeTe-based bulk thermoelectrics

Complex multicomponent systems based on PbTe, SnTe, and GeTe are of great interest for infrared devices and high-temperature thermoelectric applications. A deeper understanding of the atomic and electronic structure of these materials is crucial for explaining, predicting, and optimizing their properties, and to suggest new materials for better performance. In this work, we present our first-principles studies of the energy bands associated with various monovalent (Na, K, and Ag) and trivalent (Sb and Bi) impurities and impurity clusters in PbTe, SnTe, and GeTe using supercell models. We find …

PbTe和SnTe中的Bi、Cr和Ag掺杂剂：通过从头算计算研究主体能带对称性对掺杂性质的影响

Bi, Cr and Ag dopants in PbTe and SnTe: impact of the host band symmetry on doping properties by ab initio calculations

本文采用密度泛函理论和大超胞方法研究PbTe与SnTe中Bi、Cr、Ag及阳离子空位的掺杂行为，并用群论解释主体能带对称性导致的电子结构差异。