Epitaxially strained SnTiO$_{3}$ at finite temperatures

TL;DR

This study maps the phase diagram of epitaxially strained SnTiO$_{3}$ at finite temperatures using combined computational methods, revealing complex phase features, triple points, and strain-induced ferroelectric property changes.

Contribution

It provides the first detailed phase diagram of SnTiO$_{3}$ under strain and temperature, highlighting the dominance of ferroelectric displacements and strain-tunable ferroelectric softness.

Findings

Identified two triple points in the phase diagram.

Ferroelectric displacements dominate over oxygen octahedron tilting.

Epitaxial strain can convert SnTiO$_{3}$ from hard to soft ferroelectric.

Abstract

Combining effective Hamiltonian and direct $ab$ $initio$ computation, we obtain the phase diagram of SnTiO$_{3}$ with respect to epitaxial strain and temperature, demonstrating the complex features of the phase diagram and providing insight into the epitaxially strained SnTiO$_{3}$, a presumably simple perovskite. In the phase diagram, two triple points are found, which may be exploited to to achieve high-performance piezoelectric effects. On the other hand, despite the inclusion of the degree of freedoms related to oxygen octahedron tilting, it is found that ferroelectric displacements dominate the structural phases over the whole strain misfit range. Finally, it is shown that the SnTiO$_{3}$ can be converted from hard to soft ferroelectrics with epitaxial strain.