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

量子材料之于21世纪，就像硅之于20世纪一样。比当今最强大的超级计算机快100万倍的计算机，或者在国家电网中毫无损失地传输电力，这是量子材料的力量将实现的未来。实现这一愿景需要开发新材料，并了解产生这种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，是这样一种有前途的材料。界面氧化物材料的一个例子是LaNiO3和SrTiO3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一个界面时，它们的原子键会绷紧，从而导致缺陷的产生，即特定氧原子的损失。这些缺陷的产生被认为是这些令人兴奋的特性的一个关键的潜在原因。在这个项目中，我们专注于了解应变和氧缺陷之间的关键相关性，以便可以随意控制缺陷。这项工作将推进怀俄明州的计算科学愿景，发展对设计量子材料的基本理解，并为“量子飞跃：引领下一次量子革命”做出贡献，这是未来十大NSF想法之一。由两种不同的复合氧化物（化学式ABO3）连接形成的界面结构包含一个界面应变，导致界面上形成氧空位。这些空位被认为是产生许多新电子特性的关键原因之一。该提案的总体目标是对SrTiO3上生长的LaNiO3的界面应变和氧空位之间的关系有一个基本的理解。这种相关性将允许通过应变随意控制空缺的稳定性（即位置和浓度）。在美国阿贡国家实验室先进光子源（APS）的原位x射线光子相关光谱（XPCS）实验和密度泛函理论计算将用于阐明LaNiOx相的相变热力学和动力学，这种相变似乎是由氧空位的有序和无序引起的。这一认识将促进对LaNiO3中金属-绝缘体转变温度的控制。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值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.