A Microscopic Model of Ferroelectricity in Stress-free PbTiO3 Ultrathin Films

TL;DR

This paper develops a microscopic model to study ferroelectricity in stress-free PbTiO3 ultrathin films, revealing stable perpendicular polarization even at minimal thickness and surface polarization enhancement.

Contribution

It introduces a first-principles-based effective Hamiltonian model to analyze ferroelectricity in ultrathin PbTiO3 films under realistic boundary conditions.

Findings

Perpendicular ferroelectric ground state exists in films as thin as three unit cells.

Surface polarization is significantly enhanced compared to bulk.

Stable ferroelectricity persists at minimal film thickness.

Abstract

The ground-state polarization of PbTiO3 thin films is studied using a microscopic effective Hamiltonian with parameters obtained from first-principles calculations. Under short-circuit electrical boundary conditions, (001) films with thickness as low as three unit cells are found to have a perpendicularly polarized ferroelectric ground state with significant enhancement of the polarization at the surface.