Materials World Network: Project Summary Disorder Tuned Quantum Phases in Topological Insulators

材料世界网络：拓扑绝缘体中无序调谐量子相的项目摘要

• 批准号: 1312483
• 负责人: Lia Krusin-Elbaum
• 金额: $ 41万
• 依托单位: CUNY City College
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2013
• 资助国家: 美国
• 起止时间: 2013-09-01 至 2018-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1312483&HistoricalAwards=false
• 关键词: Materials; World; Network; Project; Summary

TECHNICAL SUMMARY:In the last few years there has been an explosive development in materials science. It began with the theoretical prediction of a new class of three dimensional (3D) topological insulators (TIs) which are fully gapped in the bulk, and with unusual gapless protected 2D Dirac surface states. This protection arises from the linear energy-momentum dispersion, with the surface states near the Fermi surface residing on a single Dirac cone. If realized, these systems could be the Holy Grail in the fields of spintronics and fault-tolerant quantum computing. However, access to this 2D quantum matter is a challenge, owing to the difficulty of separating surface contribution from the finite conductivity of the bulk. In this MWN project supported by the Division of Materials Research, swift (~ MeV range) electron and / or proton beams will be utilized to create controlled disorder by (a) tuning the bulk carrier density and Fermi level across the Dirac point, and (b) reducing bulk conductivity by forcing Anderson localization. The former will result in charge compensation in a bulk TI. The later will test recent theoretical ideas of Quantized Anomalous Hall Effect (QAHE) and, even more remarkably, (c) test a recent prediction of a Topological Anderson Insulator - a nontrivial quantum phase with quantized conductance obtained by introducing disorder in a metal with strong spin-orbit interaction. Determining the precise dose at which this occurs should establish a new large-scale route to achieving intrinsic quantum transport of the topological surfaces states.NON-TECHNICAL SUMMARY:The ability to control the quantum mechanical properties of materials is one of the forefront challenges for material scientists and condensed matter physicists. In the past few decades several bottom-up approaches striving to engineer new materials (thereby controlling their properties) at the atomic level have been devised to achieve this goal. In this proposal a top-down material modification approach will be utilized in which a controlled amount of defects will be introduced to alter the electrical properties of topological insulators (TI's) - a newly discovered class of materials which promises to offer a robust platform for quantum computing. Owing to the unique properties of TI's disorder introduced by particle irradiation will only affect the unwanted / parasitic electrical properties of these materials, while simultaneously enhancing the desired quantum properties that will foster the realization of revolutionary electronic devices and the synthesis of novel states of matter. This proposal is an international collaboration between the condensed matter physics group of the PI at The City College of New York (CCNY) - CUNY, and groups at Ecolé Polytechnique in Palaiseau, France, with unique expertise in swift particle irradiation techniques and advanced optical spectroscopy. This collaboration combines the complementary technical strengths of materials science with particle beam technology to control and tune key electronic properties of the newly discovered functional materials class. CCNY is a federally recognized minority serving institution. Ecole Polytechnique is one of the leading institutes of higher education in France, with a decidedly international outlook. The research program will have a great educational impact on the students involved, both graduate and undergraduate, for it will facilitate international visits and exchanges that will broaden their educational range and provide training in a wide spectrum of materials synthesis and experimental characterization techniques in a collaborative spirit.

技术总结：在过去的几年里，材料科学有了爆炸性的发展。它开始于一类新的三维（3D）拓扑绝缘体（TI）的理论预测，这些绝缘体在体积上是完全带隙的，并且具有不寻常的无隙保护的2D狄拉克表面态。这种保护来自于线性能量-动量色散，费米面附近的表面态位于单个狄拉克锥上。如果实现，这些系统可能是自旋电子学和容错量子计算领域的圣杯。然而，由于难以将表面贡献与体积的有限电导率分开，因此获得这种2D量子物质是一个挑战。在由材料研究部支持的MWN项目中，将利用快速（~ MeV范围）电子和/或质子束通过（a）调整狄拉克点上的体载流子密度和费米能级，以及（B）通过强制安德森局部化来降低体电导率，从而产生受控无序。前者将导致大量TI中的电荷补偿。后者将测试量子反常霍尔效应（QAHE）的最新理论思想，更值得注意的是，（c）测试拓扑安德森绝缘体的最新预测-通过在具有强自旋轨道相互作用的金属中引入无序而获得的具有量子电导的非平凡量子相。确定发生这种情况的精确剂量应该建立一个新的大规模路线，以实现拓扑表面状态的内在量子输运。非技术摘要：控制材料的量子力学性质的能力是材料科学家和凝聚态物理学家面临的最前沿挑战之一。在过去的几十年里，一些自下而上的方法努力在原子水平上设计新材料（从而控制它们的性能），以实现这一目标。在这项提案中，将利用自上而下的材料改性方法，其中将引入受控量的缺陷来改变拓扑绝缘体（TI）的电气特性-这是一种新发现的材料，有望为量子计算提供强大的平台。由于粒子辐照引入的TI无序的独特性质，它只会影响这些材料的不需要的/寄生的电特性，同时增强所需的量子特性，这将促进革命性电子器件的实现和新物质状态的合成。 该提案是纽约城市学院（CCNY）- CUNY PI凝聚态物理小组与法国帕莱索理工学院小组之间的国际合作，该小组在快速粒子辐射技术和先进光学方面拥有独特的专业知识光谱学。这项合作将材料科学与粒子束技术的互补技术优势相结合，以控制和调整新发现的功能材料类的关键电子特性。CCNY是联邦政府认可的少数民族服务机构。Ecole Polytechnique是法国领先的高等教育机构之一，具有明显的国际视野。该研究计划将对研究生和本科生产生巨大的教育影响，因为它将促进国际访问和交流，扩大他们的教育范围，并以合作精神提供广泛的材料合成和实验表征技术培训。