Switching a polar metal via strain gradients

TL;DR

This paper explores how strain gradients can induce switching in polar metals, specifically LiOsO₃, using first-principles calculations and a novel approach to compute flexocoupling coefficients, potentially enabling electric control over band topology.

Contribution

It introduces a new method to compute flexocoupling coefficients in polar metals and demonstrates the possibility of switching a polar metal via strain gradients.

Findings

Flexocoupling coefficients computed with high accuracy.

A critical bending radius for switching LiOsO₃ estimated.

Switching mechanism comparable to ferroelectric materials like BaTiO₃.

Abstract

Although rare, spontaneous breakdown of inversion symmetry sometimes occurs in a material which is metallic: these are commonly known as polar metals or ferroelectric metals. Their 'polarization', however, cannot be switched via an electric field, which limits the experimental control over band topology. Here we shall investigate, via first-principles theory, flexoelectricity as a possible way around this obstacle with the well known polar metal LiOsO$_3$. The flexocoupling coefficients are computed for this metal with high accuracy with a completely new approach based on real-space sums of the inter-atomic force constants. A Landau-Ginzburg-Devonshire-type first-principles Hamiltonian is built and a critical bending radius to switch the material is estimated, whose order of magnitude is comparable to that of BaTiO$_3$.