Feeble Metallicity and Robust Semiconducting Regime in Structurally Sensitive Ba(Pb, Sn)O$_3$ Alloys

TL;DR

This study uses density functional calculations to explore how structural modifications and alloying affect the electronic phases of Ba(Pb, Sn)O$_3$, revealing pathways to induce insulating states in metallic BaPbO$_3$ and clarifying its topological properties.

Contribution

It demonstrates how symmetry lowering, pressure, and alloying can induce insulating phases in BaPbO$_3$, and clarifies that Sn substitution does not lead to topological insulator behavior.

Findings

BaSnO$_3$ is insulating, BaPbO$_3$ is metallic.

Insulating phases can be achieved by symmetry lowering, pressure, or alloying.

Sn substitution does not produce topological insulator phase.

Abstract

Density functional calculations are carried out to study the symmetry and substitution-driven electronic phase transition in BaPb$_{1-x}$Sn$_x$O$_3$. Two end members BaSnO$_3$ and BaPbO$_3$, are found to be insulating and metallic, respectively. In the latter case, the metallicity arises with the presence of an electron pocket, formed by Pb-s dominated conduction band edge, and a hole pocket formed O-p dominated valence bands. While electron carriers are found to be highly mobile, the hole carriers are localized. Our study reveals that an insulating phase can be realized in the metallic cubic BaPbO$_3$ in three ways in order to explore optoelectronic properties. Firstly, by lowering the symmetry of the lattice to monoclinic through rotation and tilting of the PbO$_6$ octahedra. Secondly, by hydrostatic pressure, and thirdly by alloying with Sn substitution. The presence of soft phonon modes implies the plausibility of symmetry lowering structural transitions. Furthermore, unlike the earlier reports, we find that Sn substituted BaPbO$_3$ cannot exhibits topological insulator phase due to absence of the band inversion.