The formation of a two-dimensional electron gas at oxide interfaces as a consequence of polar discontinuities has generated an enormous amount of activity due to the variety of interesting effects it gives rise to. Here we study under what circumstances similar processes can also take place underneath ferroelectric thin films. We use a simple Landau model to demonstrate that in the absence of extrinsic screening mechanisms a monodomain phase can be stabilized in ferroelectric films by means of an electronic reconstruction. Unlike in the LaAlO$_3$/SrTiO$_3$ heterostructure, the emergence with thickness of the free charge at the interface is discontinuous. This prediction is confirmed by performing first principles simulations of free standing slabs of PbTiO$_3$. The model is also used to predict the response of the system to an applied electric field, demonstrating that the two-dimensional electron gas can be switched on and off discontinuously and in a non-volatile fashion. Furthermore, the reversal of the polarization can be used to switch between a two-dimensional electron gas and a two-dimensional hole gas, which should, in principle, have very different transport properties. We discuss the possible formation of polarization domains and how such configuration competes with the spontaneous accumulation of free charge at the interfaces.
Tuning exciton emission via ferroelectric polarization at a heterogeneous interface between a monolayer transition metal dichalcogenide and a perovskite oxide membrane
Multilevel recording in Bi-deficient Pt/BFO/SRO heterostructures based on ferroelectric resistive switching targeting high-density information storage in nonvolatile memories
Topological Hall Effect Induced by Chiral Spin Textures at the Ferroelectric/Ferromagnetic Interface
National Laboratory of Solid State Microstructures, Collaborative Innovation Center of Advanced Microstructures, School of Physics, Nanjing University（南京大学物理学院固态微结构国家重点实验室，先进微结构协同创新中心）；Beijing National Center for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences（中国科学院物理研究所，北京凝聚态物理国家研究中心）
Scaleability of dielectric susceptibility $ε_{zz}$ with the number of layers and additivity of ferroelectric polarization in van der Waals semiconductors
Artificial two-dimensional polar metal by charge transfer to a ferroelectric insulator
在单一系统中集成多种特性对于电子设备的持续发展至关重要。然而，某些物理性质在本质上是相互排斥的。在这里，我们报告的两个看似相互排斥的属性-极性和二维导电性-在铁电Ba $_{0.2}$ Sr $_{0.8}$ TiO $_3$薄膜在LaAlO $_3$ /Ba $_{0.2}$ Sr $_{0.8}$ TiO $_3$界面在室温下共存。一个约3.2 nm的Ba $_{0.2}$ Sr $_{0.8}$ TiO $_3$薄膜的极性保持与二维移动载流子密度约0.05电子每晶胞。我们表明，电子重建之间的竞争导致的内置电场的LaAlO $_3$和Ba $_{0.2}$ Sr $_{0.8}$ TiO $_3$的极化是负责这种不寻常的二维导电极性相。通过电子重构在氧化物界面处利用互斥性质的一般概念可能适用于其他强相关的氧化物界面，从而为新型纳米电子学中的新功能纳米材料的应用打开窗口。
