Abstract
A previously unreported Pb-based perovskite is obtained by high-pressure and high-temperature synthesis. This material crystallizes in the cubic structure at room temperature, making it distinct from typical Pb-based perovskite oxides with a structural distortion. exhibits a metallic behavior down to 0.1 K with an unusual -sublinear dependence of the electrical resistivity. Moreover, a large specific heat is observed at low temperatures accompanied by a peak in around 10 K, in marked contrast to the isostructural metallic system . These transport and thermal properties for , taking into account anomalously large Pb atomic displacements detected through diffraction experiments, are attributed to a low-energy vibrational mode, associated with incoherent off-centering of lone-pair cations. We discuss the unusual behavior of the electrical resistivity in terms of a polaronlike conduction, mediated by the strong coupling between conduction electrons and optical phonons of the local low-energy vibrational mode.
- Received 16 December 2016
- Revised 2 March 2017
DOI:https://doi.org/10.1103/PhysRevB.95.155105
©2017 American Physical Society