Temperature dependent ferroelectricity in strained KTaO3 with machine learned force field

TL;DR

This study uses machine learning-enhanced simulations to explore how strain induces ferroelectricity in KTaO3, revealing strain's critical role in stabilizing ferroelectric phases up to room temperature.

Contribution

It introduces a combined density functional theory and machine learned force field approach to accurately study strain-induced ferroelectricity in KTaO3, including anharmonic effects.

Findings

Strain induces ferroelectric polarization in KTaO3.

Higher-order anharmonic effects are significant in the phase transition.

Ferroelectricity can be stabilized up to 300 K with appropriate strain.

Abstract

Ferroelectric materials are a class of dielectrics that exhibit spontaneous polarization which can be reversed under an external electric field. The emergence of ferroelectric order in incipient ferroelectrics is a topic of considerable interest from both fundamental and applied perspectives. Among the various strategies explored, strain engineering has been proven to be a powerful method for tuning ferroelectric polarization in materials. In the case of KTaO3, first principles calculations have suggested that strain can drive a ferroelectric phase transition. In this study, we investigate the impact of in-plane uniaxial and biaxial strain, ranging from 0% to 1%, on pristine KTaO3 to explore its potential for ferroelectricity induction via inversion symmetry breaking. By integrating density functional theory calculations with the stochastic self-consistent harmonic approximation assisted by on the fly machine learned force field, we obtain accurate structural information and dynamical properties under varying strain conditions while incorporating higher-order anharmonic effects. Employing the Berry phase method, we obtained the ferroelectric polarization of the strained structures over the entire temperature range up to 300 K. Our findings provide valuable insights into the role of strain in stabilizing ferroelectricity in KTaO3, offering guidance for future experimental and theoretical studies on strain-engineered ferroelectric materials.