Tunable vertical ferroelectricity and domain walls by interlayer sliding in $\beta$-ZrI${}_2$

Abstract

Vertical ferroelectricity where a net dipole moment appears as a result of in-plane ionic displacements has gained enormous attention following its discovery in transition metal dichalcogenides. Based on first-principles calculations, we report on the evidence of robust vertical ferroelectricity upon interlayer sliding in layered semiconducting $\beta$-ZrI${}_2$, a sister material of polar semimetals MoTe${}_2$ and WTe${}_2$. The microscopic origin of ferroelectricity in ZrI${}_2$ is attributed to asymmetric shifts of electronic charges within a trilayer, revealing a subtle interplay of rigid sliding displacements and charge redistribution down to ultrathin thicknesses. We further investigate the variety of ferroelectric domain boundaries and predict a stable charged domain wall with a quasi-two-dimensional electron gas and a high built-in electric field that can increase electron mobility and electromechanical response in multifunctional devices. Semiconducting behaviour and a small switching barrier of ZrI${}_2$ hold promise for novel ferroelectric applications, and our results provide important insights for further development of slidetronics ferroelectricity.

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• Cluster Sliding Ferroelectricity in Trilayer Quasi-Hexagonal C${}_{60}$
• Electro-optic effects in some sliding ferroelectrics