标题： 扭曲氧化物双层中的极化涡旋、电荷调制、平带和莫尔磁性的预测 显示英文标题

标题： Prediction of polarization vortices, charge modulation, flat bands, and moiré magnetism in twisted oxide bilayers

摘要： 扭曲范德华化合物的莫尔超晶格最近引起了广泛关注，突显了非常规超导性和新电子相的出现。然而，通过将复杂氧化物材料引入扭曲异质结构中，莫尔现象的范围可以大大扩展。在本研究中，受近期自由悬挂氧化物膜合成突破的启发，我们探讨了扭曲氧化物双层中的新兴结构和电子特性。我们专注于经典的钙钛矿氧化物SrTiO3，并设计了具有层间相对扭转的SrTiO3双层。使用密度泛函理论计算，我们预测了由扭转驱动的SrTiO3双层界面处的涡旋-反涡旋极化图案的出现。我们还预测了由于局部配位变化而引起的界面Ti离子电荷调制，该变化遵循莫尔图案。此外，我们预测在大扭转角下会出现平带以及与莫尔周期性电荷密度相关的局域电子态，这些来源于层间键合效应导致的悬空键的形成。最后，我们预测空穴掺杂会引发原本非磁性的SrTiO3中的非常规d0磁性，这是由高密度O-p带的交换分裂驱动的，并产生具有莫尔周期性的自旋密度。这些结果展示了可能出现在莫尔工程氧化物异质结构中的广泛新兴现象，显示出这些材料系统在进一步基础研究和潜在应用方面的深远前景。 显示英文摘要

摘要： The recent surge of interest in moir\'e superlattices of twisted van der Waals compounds has spotlighted the emergence of unconventional superconductivity and novel electronic phases. However, the range of moir\'e phenomena can be dramatically expanded by incorporating complex oxide materials into twisted heterostructures. In this study, motivated by the recent breakthroughs in synthesis of free-standing oxide membranes, we explore the emergent structural and electronic properties of twisted oxide bilayers. We focus on the classic perovskite oxide, SrTiO3, and design SrTiO3 bilayers with a relative twist between the individual layers. Using density functional theory calculations, we predict the appearance of vortex-antivortex polarization patterns at the interface of the SrTiO3 bilayers driven by twist. We also predict charge modulation of the interfacial Ti ions induced by varying local coordination which follow the moir\'e pattern. Furthermore, we forecast the emergence of flat bands at large twist angles and the associated localized electronic states with moir\'e-periodic charge density, originating from the interlayer bonding effects resulting in the formation of dangling bonds. Finally, we predict that hole doping induces unconventional d0 magnetism in otherwise nonmagnetic SrTiO3, driven by the exchange splitting of the high-density O-p bands and producing the spin density with moir\'e periodicity. These results demonstrate a broad landscape of emergent phenomena which may occur in moir\'e-engineered oxide heterostructures showing far-reaching perspectives of these material systems for further fundamental studies and potential applications.