This article briefly reviews recent developments of Landau-Ginzburg theory to ferroelectric phase transitions in superlattices. An overview of the contributions of Landau-type theory to study ferroelectric superlattices is given. Recent findings from first-principles calculations and experiments on intermixing, local polarization coupling and polar discontinuity at interfaces that are not address in these contributions are highlighted. This is followed by a review of recent developments of Landau-Ginzburg theory that addresses these emergent phenomena at interfaces, which is the focus of this review article. The Landau-Ginzburg approach to ferroelectric superlattices with spatial distribution of polarization is outlined. It describes the formation of intermixed layer with properties different from those of both layers. These intermixed layers are mutually coupled through the local polarization at interfaces. Polarization continuity or continuity at interfaces is determined by the nature of the intermixed layer formed at the interface region. Recent results obtained in investigating superlattices comprised primarily of ferroelectric and paraelectric materials are discussed. The results include modulated polarizations, phase transitions, dielectric susceptibilities and switching behaviors.
Accuracy of first-principles interatomic interactions and predictions of ferroelectric phase transitions in perovskite oxides: Energy functional and effective Hamiltonian