Electro-optical effect based liquid crystal devices have been extensively used in optical modulation techniques, in which the Kerr coefficient reflects the sensitivity of the liquid crystals and determines the strength of the device operational electric field. The Peterlin-Stuart theory and the O’Konski model jointly indicate that a giant Kerr coefficient could be obtained in a material with both a large geometrical anisotropy and an intrinsic polarization, but such a material is not yet reported. Here we reveal a ferroelectric effect in a monolayer two-dimensional mineral vermiculite. A large geometrical anisotropy factor and a large inherent electric dipole together raise the record value of Kerr coefficient by an order of magnitude, till 3.0 × 10−4 m V−2. This finding enables an ultra-low operational electric field of 102∼104 V m−1 and the fabrication of electro-optical devices with an inch-level electrode separation, which is not practical previously. Because of its high ultraviolet stability (decay < 1% under ultraviolet exposure of 1000 hours), large-scale, and energy-efficiency, prototypical displayable billboards have been fabricated for outdoor interactive scenes. The work provides new insights for both liquid crystal optics and two-dimensional ferroelectrics.

中文翻译：

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具有二维铁电部分的无机液晶分散体

基于电光效应的液晶器件已广泛应用于光调制技术，其中克尔系数反映了液晶的灵敏度并决定了器件工作电场的强度。 Peterlin-Stuart理论和O'Konski模型共同表明，在具有大几何各向异性和本征极化的材料中可以获得巨大的克尔系数，但这种材料尚未见报道。在这里，我们揭示了单层二维矿物蛭石中的铁电效应。大的几何各向异性因子和大的固有电偶极子共同将克尔系数的记录值提高了一个数量级，达到3.0 × 10−4 m V−2。这一发现能够实现 102∼104 V m−1 的超低工作电场，并能够制造具有英寸级电极间距的电光器件，这在以前是不切实际的。由于其高紫外线稳定性（在紫外线照射1000小时下衰减<1%）、大规模和节能，原型可显示广告牌已被制造用于户外互动场景。这项工作为液晶光学和二维铁电体提供了新的见解。