Emphanitic anharmonicity in PbSe at high temperature and the anomalous electronic properties in the PbQ (Q=S, Se, Te) system

TL;DR

This study investigates the high-temperature anharmonic local structure of PbSe using PDF analysis and DFT, revealing emphanitic behavior and its potential influence on the material's electronic properties within the PbQ system.

Contribution

It provides the first detailed analysis of emphanitic anharmonicity in PbSe and links local structural distortions to electronic property anomalies in the PbQ system.

Findings

PbSe exhibits significant anharmonicity with off-centering along [100] directions.

The emphanitic response in PbSe is smaller than in PbS and PbTe.

DFT shows a correlation between band gap and [100] dipolar distortion amplitude.

Abstract

The temperature dependence of the local structure of PbSe has been investigated using pair distribution function (PDF) analysis of x-ray and neutron powder diffraction data and density functional theory (DFT) calculations. Observation of non-Gaussian PDF peaks at high temperature indicates the presence of significant anharmonicity, which can be modeled as Pb off-centering along [100] directions that grows on warming similar to the behavior seen in PbTe and PbS and sometimes called emphanisis. Interestingly, the emphanitic response is smaller in PbSe than in both PbS and PbTe indicating a non-monotonic response with chalcogen atomic number in the PbQ (Q=S, Se, Te) series. The DFT calculations indicate a correlation between band gap and the amplitude of [100] dipolar distortion, suggesting that emphanisis may be behind the anomalous composition and temperature dependencies of the band gaps in this series.