Electric-field switching of polar displacements in a newly designed polar metal

Abstract

Polar metals, especially those containing oxygen, are rare. Unlike ferroelectrics, using electric fields to switch polar displacements in a polar metal is difficult because applying a voltage creates an electric current in metals. Here we combine first-principles calculations and crystal structure search method to design a new polar metal and demonstrate 180\(^{\circ}\) electric-field switching of its polar displacements. We find that with two stereochemically active ions that have different valences, ordered BiPbTi\(_2\)O\(_6\) can crystallize in three polar and conducting structures, each of which can be transformed to another via pressure or strain. Furthermore, we show that by interfacing the layered structure of BiPbTi\(_2\)O\(_6\) with ferroelectrics, an electric-field switching of the in-plane polarization of ferroelectrics leads to 180\(^{\circ}\) flipping of the in-plane polar displacements of BiPbTi\(_2\)O\(_6\). Our work provides new design principles for polar metals whose polar displacements can be switched by electric fields via an interfacial coupling.