Polarization switching in sliding ferroelectrics: the roles of fluctuation and domain wall

TL;DR

This study investigates the unique polarization switching mechanisms in sliding ferroelectrics, specifically h-BN bilayers, highlighting the roles of fluctuation, domain wall dynamics, and off-diagonal Born effective charges using ab initio calculations.

Contribution

It uncovers the distinct switching rules and domain wall behaviors in sliding ferroelectrics, emphasizing the influence of symmetry-breaking perturbations and off-diagonal Born effective charges.

Findings

Perpendicular ionic movement driven by off-diagonal Born effective charge.

Symmetry-breaking perturbations facilitate avalanche-like switching.

Large off-diagonal Born effective charge causes domain wall wriggling.

Abstract

Sliding ferroelectricity is highly attractive for its low energy barriers and fatigue resistance. As the origin of these exotic properties, its unconventional switching dynamics remains poorly understood: how an electric field drives a perpendicular sliding? Taking $h$-BN bilayer as a model system, its switching dynamics is studied using \textit{ab initio} calculations. The off-diagonal Born effective charge leads to the perpendicular relationship between the electric field and ionic movements. Interestingly, the rules of intrinsic coercive field are distinct between $h$-BN bilayer and conventional ferroelectrics. For $h$-BN bilayer, any perturbation breaking the in-plane symmetry plays a key role to assist the avalanche-like switching dynamics. Moreover, the exotic large off-diagonal Born effective charge near the $P=0$ intermediate state results in a wriggling motion of domain walls in $h$-BN bilayer. Our results reveal the key factors in the ferroelectric switching of sliding ferroelectrics at room temperature.