Correlated local dipoles in PbTe
| Autor: | Simon J. L. Billinge, Boris Sangiorgio, Thomas Weber, Arkadiy Simonov, Mercouri G. Kanatzidis, Michael Fechner, Christos D. Malliakas, Emil Bozin, Nicola A. Spaldin |
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| Jazyk: | angličtina |
| Rok vydání: | 2017 |
| Předmět: |
Condensed Matter - Materials Science
Materials science Physics and Astronomy (miscellaneous) Condensed matter physics Scattering Materials Science (cond-mat.mtrl-sci) FOS: Physical sciences 02 engineering and technology 021001 nanoscience & nanotechnology 01 natural sciences Symmetry (physics) Ion Lead telluride Molecular dynamics chemistry.chemical_compound Dipole chemistry Local symmetry 0103 physical sciences Thermoelectric effect General Materials Science 010306 general physics 0210 nano-technology |
| Popis: | We present a combined single-crystal x-ray diffuse scattering and ab-initio molecular dynamics study of lead telluride, PbTe. Well-known for its thermoelectric and narrow-gap semiconducting properties, PbTe recently achieved further notoriety following the report of an unusual off-centering of the lead atoms, accompanied by a local symmetry breaking, on heating. This observation, which was named emphanisis, ignited considerable controversy regarding the details of the underlying local structure and the appropriate interpretation of the total scattering experiments. In this study, we demonstrate close agreement between our diffuse scattering measurements and our calculations, which allows us to analyze features such as higher-order correlations that are accessible in the simulations but not experimentally. This allowed us to discover an unusual correlated local dipole formation extending over several unit cells with an associated local reduction of the cubic symmetry in both our x-ray diffuse scattering measurements and our molecular dynamics simulations. Importantly, when averaged spatially or temporally, the most probable positions for the ions are at the centers of their coordination polyhedra. Our results therefore clarify the nature of the local symmetry breaking, and reveal the source of the earlier controversy regarding the existence or absence of off-centering. Finally, we provide an interpretation of the behavior in terms of coupled soft optical and acoustic modes, which is linked also to the high thermoelectric performance of PbTe. Revision of the paper, results unchanged, improved clarity of the arguments and results |
| Databáze: | OpenAIRE |
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