Ferroelectricity-mediated electromechanical coupling in boron nitride multilayers
The recent discovery of sliding ferroelectricity in van der Waals(vdW)materials has attracted tremendous interest owing to its potential for miniaturizing functional devices with atomic thicknesses.However,the practical applications of this intriguing property are largely hindered by its inherently small electric polarization resulting from weak vdW coupling between the component layers.Using boron nitride(BN)multilayers as a prototype,our ab initio calculations demonstrate that vertical pressure can substantially enhance sliding ferroelectricity.Specifically,a moderate pressure of 4.63 GPa can increase the electric polarization by 125.58％in bilayers and 104.79％in trilayers.Furthermore,when the multilayers are bent,the ferroelectricity can be further coupled with flexoelectricity to yield an amplified net polarization.Notably,the pressure-enhanced electric polarization of ferroelectricity can narrow the band gap of bent BN multilayers without requiring an external electric field.These findings present sliding ferroelectricity as a novel degree of freedom for manipulating electromechanical coupling in vdW materials.
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