Discovery of New Quantum Materials: Topological Metals, Insulators, and Superconductors

电子设备在我们的日常生活中无处不在：手机、娱乐系统、导航系统、医疗辅助设备以及网上银行等计算机化服务。 设备功能由通过每个设备中的电子组件的电流控制，这取决于组件中使用的材料。 例如，在电子学中广泛使用的晶体管是由半导体制成的，这允许简单地控制电子可用的电子状态。 电子态的性质受电子电荷、材料中原子的周期性排列、电子的内部轨道和自旋运动之间的复杂相互作用以及这些轨道和自旋运动之间的耦合（对于该提议特别重要）的支配。 例如，在绝缘体中，电子不能在样品内部流动，因为没有可用的电子态。 然而，如果存在强的自旋轨道耦合，则在样品的表面上可以存在可用的电子态。 这类最近发现的材料被称为拓扑绝缘体，因为表面态是与电子量子力学波函数拓扑结构相关的量子物理学的表现。 在上下文中，术语“拓扑”意味着在有限温度下对固体中可能的杂质的鲁棒性。即使在室温下，在不纯的样品中，拓扑绝缘体的表面上也可能出现有限的电导率，这使得这种材料对未来一代的电子元件有吸引力。 如果金属和超导体被赋予由自旋-轨道相互作用产生的类似拓扑保护，则类似的稳健量子态可能出现在金属和超导体中，以产生所谓的拓扑金属和拓扑超导体。 我的研究小组对这些和其他多体电子系统进行理论研究。 多年来，我们一直在发明和开发技术，使我们能够理解拓扑绝缘体、金属和超导体以及各种磁性材料的基本原理和基本成分。 我们最近已经表明，我们的方法已经发展到我们可以开始预测新的拓扑材料的地步，本提案的目标是应用我们的方法来发现和预见新的量子材料，这些材料可以使用现代材料制造方法（如薄膜和人工超晶格生长）进行量身定制，以优化所需的功能。 新的量子异质结构和超导体与拓扑材料之间的新界面也将被研究。 这项研究将涉及并帮助培养下一代理论材料科学家，使他们接触到广泛的材料思想和技术。

Electronic devices are everywhere in our daily life: in cell phones, entertainment systems, navigation systems, medical aids, and computerized services such as online banking. Device functionality is controlled by the flow of electric current through the electronic components in each device, and this depends on the materials used in the components. For example, transistors widely used in electronics are made of semiconductors, which allow simple control of the electronic states available to the electrons. The properties of electronic states are governed by a complex interplay between the electron's charge, the periodic arrangements of atoms in the material, internal orbital' and spin' motions of the electrons and, particularly important for this proposal, the coupling between these orbital and spin motions. For instance, in insulators, electrons cannot flow in the interior of a sample because there are no available electronic states. If there is strong spin-orbit coupling, however, there can be available electronic states on the surface of the sample. This recently-discovered class of materials is called topological insulators', because the surface states are a manifestation of quantum physics related to the topology of the electron's quantum-mechanical wave function. Contextually, the term topological' implies robustness against possible impurities in solids at finite temperatures finite electrical conductivity could occur on the surface of topological insulators even at room temperature in impure samples making such materials attractive for a future generation of electronic components. Analogous robust quantum states may occur in metals and superconductors if they are endowed with similar topological protection arising from spin-orbit interactions, to produce so-called topological metals and topological superconductors. My research group does theoretical research on these and other many-body electron systems. We have spent many years inventing and developing techniques that have allowed us to understand the fundamental principles and basic ingredients that operate in topological insulators, metals, and superconductors, and in diverse magnetic materials. We have recently shown that our methods have developed to the point where we can begin to predict new topological materials, and the goal of the present proposal is to apply our methods to discover and foresee new quantum materials that can be tailor-made using modern materials-fabrication methods, such as thin-film and artificial super-lattice growth, to optimize desired functionalities. New quantum hetero-structures and novel interfaces between superconductors and topological materials will also be investigated. This research will involve and help to train the next generation of theoretical materials scientists by exposing them to a broad range of materials ideas and techniques.**