We investigated the multiferroic properties of a hydrogenated graphene bilayer using first-principles calculations. The proposed material is composed of one fully hydrogenated and one semi-hydrogenated graphene monolayer. Inside the van der Waals gap, hydrogen atoms are only adsorbed on either the top or the bottom layer of graphene, thus breaking the centrosymmetry. The calculated electric polarization is 0.137 × 10⁻¹⁰ C m⁻¹, with the transition barrier of switching the polarization being 393 meV per formula unit. We showed that ferroelectricity can be preserved down to atomic thickness. We also studied the domain wall energy and its migration for various domain wall densities, and our results indicate a robust polarization configuration against room temperature thermal fluctuation. As graphene is known to be able to sustain large strain, we further explored ferroelectricity tuning via strain, and found that the polarization can be effectively tuned up to 20% without perturbing the polarization switching barrier. Our results suggest a realizable multiferroic two-dimensional material using the most used two-dimensional material, graphene.

中文翻译：

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多铁氢化石墨烯双层

我们使用第一性原理研究了氢化石墨烯双层的多铁性。所提出的材料由一层完全氢化和一层半氢化的石墨烯单层组成。在范德华间隙内，氢原子仅吸附在石墨烯的顶层或底层，从而破坏了中心对称性。计算出的电极化为0.137×10 ^-10 C m ^-1，极化转换的过渡势垒为每个公式单位393 meV。我们表明铁电可以保留到原子厚度。我们还研究了畴壁能量及其对于各种畴壁密度的迁移，我们的结果表明了针对室温热波动的稳健极化结构。由于已知石墨烯能够承受较大的应变，因此我们进一步探讨了通过应变进行铁电调谐的方法，发现可以有效地将极化调整到20％，而不会干扰极化切换的障碍。我们的结果表明使用最常用的二维材料石墨烯可实现的多铁性二维材料。