Fate of Topological Semimetals in the Presence of Magnetism

非技术摘要：该项目由材料研究部的固态与材料化学和凝聚态物理计划支持，提出了一种系统的方法来合成一类名为磁性拓扑半金属的新量子材料。这些材料的特征在于具有极化磁矩的高度移动的电子的小浓度。由于这些极化电子的浓度小，迁移率高，在大多数小型实验室能够达到的低磁场和中等温度下可以观察到量子效应。磁性拓扑半金属中的主要量子效应是它们的磁序决定了它们的导电性，反之亦然。因此，它们可以作为磁性开关，存储器或传感器，能够在非常小的磁场和中等温度下工作，这是最有用的应用范围。该项目依赖于理论计算，材料合成和表征之间的反馈回路，通过化学，物理和材料科学技术的组合。该项目的跨学科性质为年轻科学家提供了一个独特的教育平台，从博士后到研究生和本科生。PI设计了一门新的跨学科课程，向两个学科的研究生教授新型量子材料的化学和物理学。PI有意识地努力将他的研究与社会联系起来，在几个图书馆举办公开讲座和演示，向公众解释材料的物理和化学。技术摘要：虽然目前大多数拓扑半金属的研究都集中在非磁性金属间化合物上，PI希望故意采取不同的轨迹来看待具有拓扑势的磁性化合物。在这个项目中的材料探索利用最近的进展，在理论分类的拓扑系统的基础上的晶体和时间反演对称性。该项目的影响是通过将磁性与狄拉克/外尔物理学系统地结合起来，开辟了拓扑材料设计的新方向。由于非磁性半金属领域的快速发展，该项目特别及时。最终目标是设计新型电子相，例如手性导体，其通过材料的内部分子场稳定，而不需要外部磁场。该项目依赖于材料合成，X射线晶体学，物理测量，电子显微镜和DFT计算之间的反馈回路，以确定候选材料，生长高质量的单晶，并对其进行彻底的表征。PI实验室的跨学科环境提供了从本科到博士后水平的独特教育环境。与这项研究有关，PI为物理和化学研究生开发了一门名为“从键到带”的新课程，以演示原子和分子之间的键合形成扩展固体。

Non-technical Abstract:This project, which is supported by the Solid State and Materials Chemistry and Condensed Matter Physics programs of the Division of Materials Research, puts forward a systematic way to synthesize a new class of quantum materials named magnetic topological semimetals. These materials are characterized by a small concentration of highly mobile electrons with polarized magnetic moments. As a result of the small concentration and the high mobility of these polarized electrons, quantum effects can be observed at low magnetic fields and moderate temperatures within the reach of most small laboratories. The main quantum effect in the magnetic topological semimetals is that their magnetic order determines their electrical conduction and vice versa. Therefore, they can act as magnetic switches, memories, or sensors capable of operating at very small magnetic fields and moderate temperatures which is the most useful range for applications. The project relies on a feedback loop between theoretical calculations, materials synthesis, and characterizations through a combination of chemistry, physics, and materials science techniques. The cross-disciplinary nature of this project provides a unique educational platform for young scientists, from postdocs to graduate and undergraduate students. A new interdisciplinary course is designed by the PI to teach the chemistry and the physics of novel quantum materials to graduate students from both disciplines. The PI makes a conscious effort to connect his research to the society by presenting public lectures and demonstrations at several libraries to explain the physics and the chemistry of materials to the general public.Technical Abstract:While most of the current studies on topological semimetals are focused on non-magnetic intermetallic compounds, the PI wants to deliberately take a different trajectory to look at the magnetic compounds with topological potentials. The materials explorations in this project exploit recent advances in the theoretical classification of topological systems based on the crystalline and the time reversal symmetries. The impact of the project is to open a new direction in topological materials design by incorporating magnetism with Dirac/Weyl physics in a systematic way. The project is particularly timely due to the rapid advances in the field of non-magnetic semimetals. The final goal is to engineer novel electronic phases such as chiral conductors which are stabilized by the internal molecular field of the material without the need for an external magnetic field. The project relies on a feedback loop between material synthesis, x-ray crystallography, physical measurements, electron microscopy, and DFT calculations to identify materials candidates, to grow high quality single crystals, and to thoroughly characterize them. The interdisciplinary environment of the PI's lab provides a unique educational environment from undergraduate to postdoctoral level. Connected to this research, a new course titled "from bonds to bands" is developed by the PI for both physics and chemistry graduate students to demonstrate the formation of extended solids from bonding between atoms and molecules.