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在理解具有复杂结构和有趣功能特性的材料的基本物理学。特别是，我们将专注于在含有第二或第三行过渡金属元素（如铱）的材料中发现新的拓扑量子相。这些材料的特征在于它们的强自旋-轨道耦合，这是由电子的内禀磁矩与其运动之间的相对论相互作用引起的。自旋-轨道耦合驱动的拓扑相的最著名的例子是拓扑绝缘体。这种材料的表面可以导电，而样品的内部保持绝缘。拓扑相的这种电子性质预计对缺陷和无序非常鲁棒，使它们在基于自旋的电子学和容错量子计算中的应用非常有用。当自旋-轨道耦合能标与电子间的库仑排斥能相平衡时，就能发现更令人兴奋的物理现象。铱基材料是这两种能量尺度竞争的一个很好的物理例子。事实上，大量的奇异量子相，如拓扑半金属、超导体和具有拓扑有序的量子自旋液相已经被预测存在于铱化合物中。然而，这些理论预测的相是否存在于真实的材料中仍然是一个悬而未决的问题。我们建议对复杂铱氧化物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努力，找到这些异国情调的阶段，通过调整材料参数，如电荷载流子掺杂，外部静水压力，外延应变和高磁场。通过改变这些参数，我们将能够探索具有不同结构图案的几种铱酸盐材料的大参数空间：蜂窝晶格，烧绿石晶格和正方形晶格。一个特别的注意将支付给外延薄膜样品中找到拓扑量子相。为了检测铱化合物中的拓扑顺序，我们将依靠最先进的X射线和中子光谱方法来测量完整的动态结构因子。特别是共振非弹性X射线散射（RIXS）技术，这是迅速发展成为一个强大的动量相关的光谱方法，将发挥重要作用，在我们的理解的物理iridates.新的功能特性发现在这些拓扑量子阶段，最终可以利用在未来的氧化物为基础的电子学。在过去的二十年中，外延薄膜生长技术的进步使得人们有可能设想基于复杂氧化物材料的电子学。由强电子关联和自旋轨道耦合引起的拓扑量子相的奇异性质对于氧化物基电子学的未来应用至关重要。拟议的研究也将为创新材料研究人员的培训做出重大贡献。