Two-Dimensional Antiferroelectricity in Nanostripe-Ordered <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi>In</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:mrow><mml:mrow><mml:msub><mml:mrow><mml:mi>Se</mml:mi></mml:mrow><mml:mrow><mml:mn>3</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>
Chao Xu, Yan‐Cong Chen, Xiangbin Cai, Arno Meingast, Xuyun Guo, Fakun Wang, Ziyuan Lin, Tsz Wing Lo, C. Maunders, Sorin Lazar, Ning Wang, Dangyuan Lei, Yang Chai, Tianyou Zhai, Xin Luo, Ye Zhu
Abstract
Two-dimensional (2D) layered materials have been an exciting frontier for exploring emerging physics at reduced dimensionality, with a variety of exotic properties demonstrated at 2D limit. Here, we report the first experimental discovery of in-plane antiferroelectricity in a 2D material ${\ensuremath{\beta}}^{\ensuremath{'}}\ensuremath{-}{\mathrm{In}}_{2}{\mathrm{Se}}_{3}$, using optical and electron microscopy consolidated by first-principles calculations. Different from conventional 3D antiferroelectricity, antiferroelectricity in ${\ensuremath{\beta}}^{\ensuremath{'}}\ensuremath{-}{\mathrm{In}}_{2}{\mathrm{Se}}_{3}$ is confined within the 2D layer and generates the unusual nanostripe ordering: the individual nanostripes exhibit local ferroelectric polarization, whereas the neighboring nanostripes are antipolar with zero net polarization. Such a unique superstructure is underpinned by the intriguing competition between 2D ferroelectric and antiferroelectric ordering in ${\ensuremath{\beta}}^{\ensuremath{'}}\ensuremath{-}{\mathrm{In}}_{2}{\mathrm{Se}}_{3}$, which can be preserved down to single-layer thickness as predicted by calculation. Besides demonstrating 2D antiferroelectricity, our finding further resolves the true nature of the ${\ensuremath{\beta}}^{\ensuremath{'}}\ensuremath{-}{\mathrm{In}}_{2}{\mathrm{Se}}_{3}$ superstructure that has been under debate for over four decades.