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 does an electric field drive a perpendicular sliding? Taking $h\text{−}\mathrm{BN}$ bilayer as a model system, its switching dynamics is studied using 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 $h\text{−}\mathrm{BN}$ bilayer and conventional ferroelectrics. For $h\text{−}\mathrm{BN}$ bilayer, any perturbation breaking the in-plane symmetry plays a key role to assist the avalanchelike 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 $h\text{−}\mathrm{BN}$ bilayer. Our results reveal the key factors in the ferroelectric switching of sliding ferroelectrics at room temperature.

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• Ferroelectricity
• Boron nitride
• Density functional theory