RII Track--4: Controlling Point-Defect Energetics in Complex Oxides Via Interfacial Strain

正如硅之于20世纪，量子材料之于21世纪。比今天最强大的超级计算机快一百万倍的计算机，或者说是通过国家电网传输的电力，是那种将通过量子材料的力量实现的未来。实现这一愿景需要开发新材料，并了解产生如此令人难以置信的性能的关键材料特性。界面氧化物材料，即由两种不同的氧化物材料连接而成的材料，是一种很有前途的材料。界面氧化物材料的一个例子是LaNiO_3和SrTiO_3之间的界面。由于这两种材料的原子之间的距离不同，当它们连接在一起形成界面时，它们的原子键会被应变，这可能会导致缺陷的产生，即失去特定的氧原子。这些缺陷的产生被认为是这些令人兴奋的特性的关键潜在原因。在这个项目中，我们专注于了解菌株和氧缺陷之间的关键关联，以便可以随意控制缺陷。这项工作将推进怀俄明州计算科学的愿景，发展对设计量子材料的基本理解，并为下一个十大NSF想法之一的“量子飞跃：领导下一次量子革命”做出贡献。由两个不同的复合氧化物(化学式ABO3)连接形成的界面结构包含一种界面应变，导致在界面上形成氧空位。这些空位被认为是导致许多新的电子性质的关键原因之一。该提案的首要目标是对在钛酸锶衬底上生长的LaNiO_3的界面应变与氧空位之间的关系有一个基本的了解。这种关联将允许通过应变随意控制空位的稳定性(即位置和浓度)。利用Argonne国家实验室先进光子源(APS)的原位X射线光子相关谱(XPCS)实验和密度泛函理论计算，阐明了LaNiOx相的相变热力学和动力学，它似乎是由氧空位的有序和无序引起的。这一理解将推动控制LaNiO中金属-绝缘体转变温度的科学。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

What silicon was to the 20th century, quantum materials are to the 21st. A million times faster computers than today's most powerful supercomputers, or, electricity transported across the national grid at no loss, is the sort of future that will be realized by the power of quantum materials. Realizing this vision requires developing new materials and understanding key materials features that give rise to such incredible properties. Interfacial oxide materials, i.e., those formed by joining of two different oxide materials, are one of such promising materials. An example of an interfacial oxide material is an interface between LaNiO3 and SrTiO3. Because these two materials have different distances between their atoms, when joined to form an interface, their atomic bonds are strained that can lead to creation of defects, i.e., loss of specific oxygen atoms. Creation of these defects has been proposed to be a key underlying reason of such exciting properties. In this project, we focus on understanding the critical correlation between strain and oxygen defects such that the defects could be controlled, at will. This work will advance Wyoming's vision of computational sciences, develop basic understanding of designing quantum materials, and contribute to "The Quantum Leap: Leading the Next Quantum Revolution" which is one of the next ten big NSF ideas.The interface structure formed by joining two different complex oxides (chemical formula ABO3) contains an interfacial strain which leads to formation of oxygen vacancies at the interface. These vacancies are considered to be one of key reasons inducing many novel electronic properties. The overarching goal of the proposal is to develop a fundamental understanding of the correlation between interfacial strain and oxygen vacancies in LaNiO3 grown on SrTiO3. This correlation will allow control over the stability (i.e., location and concentration) of vacancies via strain, at will. In-situ X-ray Photon Correlation Spectroscopy (XPCS) experiments at Advanced Photon Source (APS) in Argonne National Laboratory and density functional theory calculations will be used to elucidate the thermodynamics and kinetics of phase transitions in LaNiOx phases, which appears to be induced via the ordering and disordering of the oxygen vacancies. This understanding will advance the science of gaining control over the metal-insulator transition temperature in LaNiO3.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.