Topological quantum phases in complex functional materials

复杂功能材料中的拓扑量子相

• 批准号: RGPIN-2014-06071
• 负责人: Kim, YoungJune
• 金额: $ 3.06万
• 依托单位: University of Toronto
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2017
• 资助国家: 加拿大
• 起止时间: 2017-01-01 至 2018-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=633008
• 关键词: Topological; quantum; phases; complex; functional

Our research program centres on understanding the basic physics of materials with complex structures and interesting functional properties. In particular, we will focus on finding novel topological quantum phases in materials containing second or third row transition metal elements such as iridium. These materials are characterized by their strong spin-orbit coupling, which arises from the relativistic interaction between the electron’s intrinsic magnetic moment and its motion. The best-known example of a spin-orbit coupling driven topological phase is a topological insulator. This material’s surface can conduct electricity while the interior of the sample remains insulating. Such electronic properties of topological phases are expected to be extremely robust against defects and disorder, making them useful for applications in spin-based electronics and fault-tolerant quantum computing. Even more exciting physics can be found when the spin-orbit coupling energy scale is balanced against the repulsive Coulomb energy between electrons. Iridium based materials turn out to be an excellent physical example in which these two energy scales compete. In fact, a plethora of exotic quantum phases, such as topological semimetals, superconductors, and quantum spin liquid phases with topological order have already been predicted to exist in iridium compounds. However, whether any of these theoretically predicted phases exist in real materials remains an open question.We propose to carry out a systematic experimental investigation of topological quantum phases in complex iridium oxides. Our experimental approach relies on exploratory materials synthesis efforts to find these exotic phases, through tuning materials parameters such as charge carrier doping, external hydrostatic pressure, epitaxial strain, and high magnetic fields. By varying these parameters, we will be able explore a large parameter space of several iridate materials with different structural motifs: honeycomb lattice, pyrochlore lattice, and square lattice. A particular attention will be paid to find topological quantum phases in epitaxial thin film samples. To detect topological order in iridium compounds, we will rely on state-of-the art x-ray and neutron spectroscopy methods to measure the full dynamic structure factor. In particular, the resonant inelastic x-ray scattering (RIXS) technique, which is rapidly developing into a powerful momentum dependent spectroscopy method, will play a significant role in our understanding of the physics of iridates.Novel functional properties found in these topological quantum phases could eventually be harnessed in future oxide-based electronics. Advances in epitaxial thin film growth technology in the last two decades have made it possible to envision electronics based on complex oxide materials. The exotic properties of topological quantum phases arising from the strong electron correlation and spin-orbit coupling could be crucial for the future application of oxide-based electronics. The proposed research will also make a significant contribution to the training of innovative materials researchers.

我们的研究计划集中于了解具有复杂结构和有趣功能特性的材料的基本物理。特别是，我们将专注于在包含第二或第三行转变金属元件（例如虹膜元素）的材料中找到新颖的拓扑量子相。这些材料的特征是它们强的自旋轨道耦合，这是由于电子的内在磁矩与其运动之间的相对性相互作用而产生的。自旋轨耦合驱动拓扑阶段最著名的例子是拓扑绝缘体。该材料的表面可以传导电力，而样品的内部仍然是绝缘体。拓扑阶段的这种电子特性预计将对缺陷和混乱非常强大，这使其可用于基于旋转的电子设备和耐断层量子计算的应用。当旋转轨道耦合能量表平衡的基于虹膜的材料是一个很好的物理示例时，可以找到更令人兴奋的物理学。实际上，已经预测，已经预测，已经预测，已经预测，已经预测，已经预计，具有拓扑级数的拓扑半学，超导体和量子自旋液相的众多异国情调量子相已被预测存在于虹膜化合物中。但是，在实际材料中是否存在这些理论预测阶段中的任何一个。一个开放的问题。我们建议对复杂氧化虹膜中的拓扑量子相进行系统的实验研究。我们的实验方法依赖于探索性材料合成的工作，以通过调整材料参数（例如电荷载体掺杂，外部静水压力，外延菌株和高磁场）来找到这些外来的相位。通过改变这些参数，我们将能够探索几种具有不同结构基序的材料的大参数空间：蜂窝晶格，pyrochlore晶格和方格晶格。将特别注意在外延薄膜样品中找到拓扑量子阶段。为了检测虹膜化合物中的拓扑顺序，我们将依靠最先进的X射线和中子光谱法来测量完整的动态结构因子。特别是，迅速发展为强大的动量依赖的光谱法的谐振非弹性X射线散射（RIX）技术将在我们对这些拓扑量子阶段中发现的功能性能的理解中发挥重要作用。在过去的二十年中，外延薄膜生长技术的进步使得基于复杂的氧化物材料设想电子产品成为可能。强烈的电子相关性和自旋轨道耦合引起的拓扑量子相的外来特性对于将来的基于氧化物的电子产品的应用至关重要。拟议的研究还将为培训创新材料研究人员做出重大贡献。