Atomistic simulations of the incipient ferroelectric KTaO$_3$

TL;DR

This study uses atomistic simulations with an effective Hamiltonian to accurately model the dielectric response of KTaO$_3$, revealing quantum effects suppress phase transition and induce local off-center displacements with needle-like correlations.

Contribution

It introduces a quantum-aware effective Hamiltonian approach that reproduces experimental dielectric behavior without defect assumptions.

Findings

Quantum fluctuations suppress the phase transition.

Local off-center displacements with needle-like correlations are observed.

Dielectric response matches experimental data.

Abstract

A parameterized effective Hamiltonian approach is used to investigate KTaO$_3$. We find that the experimentally observed anomalous dielectric response of this incipient ferroelectric is well reproduced by this approach, once quantum effects are accounted for. Quantum fluctuations suppress the paraelectric--to--ferroelectric phase transition; it is unnecessary to introduce defects to explain the dielectric behavior. The resulting quantum-induced local structure exhibits off-center atomic displacements that display {\sl longitudinal, needle-like correlations} extending a few lattice constants.