Perturbative approach to electrocaloric effects

TL;DR

This paper introduces a perturbative Taylor series approach to understanding the electrocaloric effect, unifying small-field behaviors in ferroelectrics and antiferroelectrics, supported by first-principles simulations.

Contribution

It presents a novel perturbative formalism for electrocaloric effects, clarifying physical mechanisms and predicting subtle competing contributions in ferroelectric materials.

Findings

Unified explanation of normal and inverse EC responses

Explicit evaluation of competing contributions in PbTiO3

Validation of the theory through first-principles simulations

Abstract

We show that the electrocaloric (EC) effect -- e.g., the temperature change experienced by an insulator upon application of an electric bias -- lends itself to a straightforward interpretation when expressed as a Taylor series in the external field. Our formalism explains in a unified and simple way the most notable small-field effects reported the literature -- e.g., the so-called {\em normal} (increase of temperature under bias, as usually found in ferroelectrics) and {\em inverse} (decrease of temperature, as e.g. in antiferroelectrics) EC responses -- and clarifies their physical interpretation. We also discuss in detail second-principles simulations for prototype ferroelectric PbTiO$_{3}$, explicitly evaluating subtle predictions of the theory, such as the occurrence of competing contributions to the EC response.