Exploring Novel Electronic Structures of Topological Quantum Matter

电子材料在现代生活的几乎每个方面都发挥着巨大的作用-从超级计算机到家用电子产品-这些材料中电子的行为决定了它们丰富而不寻常的特性。从历史上看，新型电子量子材料的发现已经引起了我们生活方式和经济的革命，例如半导体的发现。最近，一种全新类型的电子材料-拓扑绝缘体-被理论预测并实验实现。拓扑绝缘体代表了量子物质的一种全新状态，与所有先前已知的状态不同。从表面上看，它们是众所周知的现成材料;但它们具有深刻的，但以前被忽视的特性，使它们如此独特。拓扑绝缘体在其纯态下，在体电子带中具有完整的能隙（因此类似于绝缘体）;而在表面上，它具有由具有线性能量-动量关系的电子形成的金属态（类似于不具有静止质量的光子！）它们的自旋极化完全由它们的运动方向决定。更戏剧性的是，这些不寻常的电子非常强大，可以在拓扑绝缘体的表面上流动，对抗任何非磁性杂质，晶体缺陷或表面扭曲。拓扑绝缘体由于其巨大的科学意义和技术潜力，近年来已成为凝聚态物理研究的热点领域之一，然而，尽管世界各国的科学家们都在不断探索这一令人兴奋的前沿领域，但要真正实现许多令人惊奇的量子现象，还存在许多挑战拓扑绝缘体的磁单极子、半电子电荷和由修正的麦克斯韦方程引起的拓扑磁电效应等，以及拓扑绝缘体在电子学、自旋电子学和热电等方面的应用前景。例如，目前的拓扑绝缘体通常具有过多的体载流子，从而防止体绝缘（这将掩盖表面电子的微妙拓扑效应）;并且小的体能隙也防止它们用于高（室温）电子器件。因此，我们希望通过开展本项目来解决这些问题，以改善现有的拓扑绝缘体的质量，并寻找更好的拓扑绝缘体，具有更大的体能隙和更稳定的在规则的环境中。我们还将探索拓扑绝缘体独特的电子和自旋性质在实际应用中的应用途径，如超低功率电子学、新型自旋电子器件、光电应用、高效热电应用和催化应用。此外，拓扑绝缘体的迅速发展也激发了其他新拓扑态的研究，如量子反常霍尔绝缘体、拓扑半金属、拓扑晶体绝缘体和拓扑超导体等。这些新的拓扑态将为更丰富的奇异量子现象打开大门（例如没有外部施加磁场的量子化霍尔电导，和奇异的马约拉纳费米子，这是他们自己的反粒子）和更多的非常规应用（从超低集成电路到未来的拓扑量子计算机）因此，我们也将在这个项目中寻找这些量子物质的新相。

Electronic materials play a tremendous role in almost every aspect of modern life - from supercomputers to household electronics - and the behavior of electrons in these materials determines their rich and unusual properties. Historically, the discoveries of novel electronic quantum materials have caused revolutions in our lifestyle and economy, such as the discovery of semiconductors. Very recently, an entirely new type of electronic materials, the topological insulator, was theoretically predicted and experimentally realized.Topological insulators represent a brand new state of quantum matter that is distinct to ALL previously known states. On the face of it, they are well-known, off the shelf materials; but they have profound, yet previously overlooked properties that make them so unique. In its pure form, a topological insulator has a full energy gap in the bulk electron band (thus like an insulator); while on the surface, it has metallic states formed by electrons with linear energy-momentum relationship (similar to photons that do not possess rest mass!) with their spin polarization completely determined by their moving directions. More dramatically, these unusual electrons are extremely robust, and can flow on the surface of topological insulators against any non-magnetic impurities, crystalline defects or surface distortions. Due to the great scientific significance and technological potential, topological insulators have grown as one of the most intensely studied fields in condensed matter physics within the last few years.However, while the scientists worldwide are advancing the frontier of this exciting field, there remain many challenges before we can actually realize the many amazing quantum phenomena (such as the magnetic monopoles, half electron charge and many topological magneto-electric effects resulted from the revised Maxwell equations in topological insulators) and practical applications (such as novel electronic, spintronic and thermoelectric applications) topological insulators promise. For examples, current topological insulators typically have excessive bulk carriers, thus prevent the bulk from being insulating (which will mask the subtle topological effects from the surface electrons); and the small bulk energy gap also prevent them from being used in high (room) temperature electronic devices. Thus we would like to solve these problems by carrying out this project to improve the quality of current topological insulators, and search for even better topological insulators with larger bulk energy gap and more stable in regular environments. We will also explore the pathways to use the unusual electronic and spin properties of topological insulators in practical applications, such as ultra-low power electronics, novel spintronic devices, optoelectronic applications, high efficiency thermoelectric applications and catalysis applications.Furthermore, the swift development of topological insulators has also inspired the study of other new topological states, such as quantum anomalous Hall insulators, topological semi-metals, topological crystalline insulators and topological superconductors, etc. These new topological states will unlock the door to even richer exotic quantum phenomena (such as quantized Hall conductance without externally applied magnetic field, and the exotic Majorana fermions that are their own anti-particles) and more unconventional applications (from ultra-low integrate circuit to future topological quantum computers) Thus we will also search for these novel phases of quantum matter in this project.