Tunable vertical ferroelectricity and domain walls by interlayer sliding in $\beta$-ZrI$_{2}$

TL;DR

This study demonstrates robust vertical ferroelectricity in layered $eta$-ZrI$_{2}$ driven by interlayer sliding, revealing potential for ultrathin ferroelectric devices and novel electronic properties through charge redistribution and domain wall engineering.

Contribution

First-principles calculations uncover the mechanism of ferroelectricity in $eta$-ZrI$_{2}$ caused by interlayer sliding and charge shifts, advancing the understanding of slidetronics ferroelectricity.

Findings

Robust vertical ferroelectricity observed in $eta$-ZrI$_{2}$.

Prediction of stable charged domain walls with high electric fields.

Semiconducting behavior with low switching barriers in 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.