Nanoscale Imaging of Topological Superconductivity in Heterostructures

非技术摘要：除了众所周知的负电荷外，电子还具有第二种称为“自旋”的性质，类似于可以指向任何方向的旋转轴。理想的拓扑绝缘体(TI)是一种材料，其内部是电绝缘的，但其表面是一种特殊的金属，其中电子自旋被阻止后向散射，从而消除了当今微电子中不必要的加热的主要来源。这些表面特性使它成为实现两种变革性未来技术的有希望的候选者：“自旋电子学”，一种替代传统电子学的非常低功率的技术，以及“量子计算”，一种快速解决计算密集型问题的全新方法。然而，在过去的5年里发现的第一代拓扑材料，已经遭受了不必要的电子通过其内部的“泄漏”，这破坏了它们有希望的表面性质。该奖项支持两组平行的实验，旨在发现完美的拓扑绝缘体，并设计拓扑和其他材料之间的界面，预计将使量子计算应用成为可能。这些实验结合了两种先进的原子尺度材料合成和表征技术：分子束外延和扫描隧道显微镜。这个项目有望从根本上促进对拓扑绝缘体的理解和对自旋电子学和量子计算的应用。该奖项还支持1名博士后研究员和1名研究生的教育和培训。技术摘要：理想的拓扑绝缘体(TI)是一种具有绝缘体的材料，但具有拓扑保护的导电表面态，其上阻止自旋极化电子的后向散射。这些特性使它成为两种未来变革性技术的有希望的候选者：可能绕过目前限制传统电子学的严重功率耗散问题的自旋电子学，以及提供了一种替代目前最好的量子比特的短消相干时间的拓扑量子计算。然而，被高度研究的第一代Bi2X3拓扑“绝缘体”由于明显不可避免的自掺杂而遭受不必要的体导。该奖项支持两种平行的实验方法来规避这些挑战。一种是使用扫描隧道显微镜(STM)来寻找真正的块状绝缘体上的拓扑表面态，例如拓扑近藤绝缘子。平行的方法是在密度泛函理论计算的指导下，利用分子束外延和扫描隧道显微镜相结合的系统来设计拓扑半金属锑-超导体异质结构。这种方法的意义在于首次实现和研究了拓扑p波超导电性，这将对更广泛的非常规超导体领域产生重大影响，并为最终寻找拓扑量子计算应用的核心马约拉纳费米子提供了一个游乐场。该奖项还支持对一名博士后研究员和一名研究生进行先进材料合成和表征技术方面的教育和培训。

Non technical Abstract: In addition to their well-known negative electric charge, electrons carry a second property called "spin", akin to an axis of rotation which may point in any direction. An ideal topological insulator (TI) is a material whose interior is electrically insulating, but whose surface is a special metal where electron spins are prevented from backscattering, removing the primary source of unwanted heating in today's microelectronics. These surface properties make TIs promising candidates to enable two transformative future technologies: "spintronics," a very low power replacement for conventional electronics, and "quantum computing," a completely new method for rapidly solving computationally intensive problems. However, the first generation of topological materials, discovered over the last 5 years, has suffered from unwanted "leakage" of electrons through their interiors, which undermines their promising surface properties. This award supports two parallel sets of experiments aimed at discovering perfect topological insulators and at engineering the interfaces between topological and other materials which are predicted to enable quantum computing applications. The experiments combine two advanced atomic-scale material synthesis and characterization techniques: molecular beam epitaxy and scanning tunneling microscopy. A fundamental advancement of the understanding and utility of topological insulators towards spintronics and quantum computing would be expected from this project. This award also supports the education and training of one postdoctoral fellow and one graduate student. Technical Abstract:An ideal topological insulator (TI) is a material with an insulating bulk, but a topologically protected conducting surface state on which spin-polarized electrons are prevented from backscattering. These properties make TIs promising candidates to enable two transformative future technologies: "spintronics," which may circumvent the severe power dissipation problems now limiting conventional electronics, and "topological quantum computing," which provides an alternative to the short decoherence times in the best present-day qubits. However, the highly-studied first-generation Bi2X3 topological "insulators" suffer from unwanted bulk conduction due to apparently unavoidable self-doping. This award supports two parallel experimental approaches to circumvent these challenges. One is to use scanning tunneling microscopy (STM) to search for topological surface states on true bulk insulators, such as topological Kondo insulators. The parallel approach is to engineer topological semimetal antimony-superconductor heterostructures using a combined molecular beam epitaxy and STM system, with guidance from density functional theory calculations. The significance of this approach lies in the first achievement and study of topological p-wave superconductivity, which would have high impact on the field of unconventional superconductors more broadly and also provide a playground for the eventual search for the Majorana fermion at the heart of topological quantum computing applications. The award also supports the education and training of one postdoctoral fellow and one graduate student in advanced material synthesis and characterization techniques.