Using first-principles-based simulations merging an effective Hamiltonian scheme with scaling, symmetry, and topological arguments, we find that an overlooked Berezinskii-Kosterlitz-Thouless ($\mathsf{B}\mathsf{K}\mathsf{T}$) phase sustained by quasicontinuous symmetry emerges between the ferroelectric phase and the paraelectric one of ${\mathrm{BaTiO}}_3$ ultrathin film, being under tensile strain. Not only do these results provide an extension of $\mathsf{B}\mathsf{K}\mathsf{T}$ physics to the field of ferroelectrics, but they also unveil their nontrivial critical behavior in low dimensions.

中文翻译：

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低维铁电体中出现的Berezinskii-Kosterlitz-Thouless相

使用基于第一原理的模拟将有效的汉密尔顿方案与缩放，对称和拓扑参数合并，我们发现被忽略的Berezinskii-Kosterlitz-Thouless（$\mathsf{乙}\mathsf{ķ}\mathsf{Ť}$）在铁电相和顺电相之一之间出现了由准连续对称性维持的相 ${\mathrm{钛酸钡}}_3$超薄膜，处于拉伸应变下。这些结果不仅提供了$\mathsf{乙}\mathsf{ķ}\mathsf{Ť}$ 铁电学领域的物理学，但它们还揭示了其在低维方面的重要特性。