Perovskite BaSnO3 has an Sn s-orbital conduction band minimum, which makes it of interest as a transparent-conducting oxide parent compound but also contraindicates the ferroelectric instability characteristic of the related compound BaTiO3. In this work, we studied the effect of (001) compressive strain on BaSnO3 using first-principles methods. We found that, with low compressive strain, symmetry breaking takes cubic BaSnO3 to a nonpolar tetragonal state, with a first-order phase transition to a hidden highly-polarized ferroelectric supertetragonal state at about -5%. Based on the facts that the mismatch of lattice constant in experiment between BaSnO3 and SrTiO3 is about -5.2% and coherent growth of BaSnO3 on SrTiO3 has been experimentally realized for BaSnO3 layers thinner than 3 unit-cells, we studied a series of SrTiO3/BaSnO3 superlattices with one or two unit-cells of BaSnO3 and several unit-cells of SrTiO3. We found that the superlattices are ferroelectric with large polarizations. We propose that the origin of ferroelectricity in the superlattices is the mechanical and electrical coupling of the BaSnO3 and SrTiO3 layers, with polarized supertetragonal state of BaSnO3 induced by compressive-strain from the SrTiO3 layers and polarization of the SrTiO3 layers by the polar BaSnO3 layers. Due to the distinctive electronic states in the BaSnO3 layers, the realization of ferroelectricity holds promise for the design of novel electronic devices.
Stabilization of highly polar BiFeO$_3$-like structure: a new interface design route for enhanced ferroelectricity in artificial perovskite superlattices
Twist-induced Out-of-plane Ferroelectricity in Bilayer Hafnia
Institute of Materials Science and Engineering, Washington University in St. Louis（华盛顿大学圣路易斯分校材料科学与工程研究所）；Department of Mechanical Engineering and Material Science, Washington University in St. Louis（华盛顿大学圣路易斯分校机械工程和材料科学系）；Department of Physics and Astronomy, University of Nebraska, Lincoln（内布拉斯加大学林肯分校物理与天文学系）；Department of Physics, Washington University in St. Louis（华盛顿大学圣路易斯分校物理系）
Ferroelectricity in Atomically Thin Metallic TaNiTe$_5$ with Ultrahigh Carrier Density
State Key Laboratory of Micro-nano Engineering Science, Key Laboratory of Artificial Structures and Quantum Control (Ministry of Education), School of Physics and Astronomy, Shanghai Jiao Tong University（上海交通大学物理与天文学院微纳工程科学国家重点实验室人工结构与量子控制教育部重点实验室）；School of Physical Science and Technology, Ningbo University（宁波大学物理科学与技术学院）；School of Physics, Zhejiang University of Technology（浙江工业大学物理学院）；Tsung-Dao Lee Institute, Shanghai Jiao Tong University（上海交通大学李政道研究所）；Collaborative Innovation Center of Advanced Microstructures（先进微结构协同创新中心）
Ferroelectric hysteresis in singly aligned graphene-hBN moiré superlattices
CIC nanoGUNE（纳米科技联合研究中心）；University of the Basque Country (UPV/EHU)（巴斯克大学）；National Institute for Materials Science（物质材料研究机构）；Centro de Física de Materiales (CFM-MPC) Centro Mixto CSIC-UPV/EHU（物质物理中心（CFM-MPC）CSIC-巴斯克大学联合中心）
Electron-lattice coupling contributions to polarization switching in charge-order-induced ferroelectrics
我们进行第一性原理密度泛函理论计算来阐明基于（SrVO $_3$）$_1$（LaVO $_3$）$_1$超晶格的电荷有序诱导铁电体的极化开关机制。我们发现，晶格弛豫的比荷有序状态可以“锁定”的状态，使非绝热切换到不同的CO变体大力禁止，在某些情况下，甚至使绝热切换的能量障碍大得令人望而却步。我们将电荷有序材料分为两种类型，多面体呼吸和偏心位移，基于晶格模式的类型最强耦合的电荷有序。我们证明了由外电场引起的非绝热电子跳跃仅在偏心位移型电荷有序诱导铁电体中才能发生。这成功地解释了LuFe $_2$ O $_4$和Fe $_3$ O $_4$不同的开关行为。这些结果提供了一个新的理解的极化开关机制的电荷有序诱导铁电材料的设计和发现提供了指导，并提出了一种策略，实现“电子铁电性”与极化开关的电子，而不是晶格的时间尺度。
