CAREER: Probing and Braiding Chiral Majorana Fermions in Quantum Anomalous Hall Insulator-Superconductor Hybrid Structures

非技术摘要：对高计算能力的快速增长的需求要求彻底改变基于硅晶体管的传统计算机的范式。量子计算机利用量子物理来存储信息和执行计算，预计将比传统计算机效率高得多，因此功能也更强大。量子计算的一个吸引人的方案涉及一类新发现的材料，称为拓扑绝缘体，其中内部是绝缘的，但表面是导电的。将磁性元素加入到这种拓扑绝缘体样品中，可以实现一种奇怪的现象，即量子反常霍尔效应。在这种状态下，表面电子被限制在样品的边缘，没有阻力地流动。已经预测，利用量子反常霍尔绝缘体的这种无电阻边缘电流的装置可以实现量子计算。该项目旨在验证这一预测。面向研究生和本科生、K-12学生和教师以及普通公众的积极教育和推广计划是计划工作的组成部分。技术摘要：量子反常霍尔绝缘体的自旋极化无耗散边缘态与常规超导体的耦合被预测为包含拓扑超导相，该相支持样品表面或边缘的无间隙Majorana费米子激发。拓扑超导可以揭示变革性的新物理，如非阿贝尔统计，并为拓扑量子计算提供新的体系结构。在这个项目中，主要的研究人员在一个微米大小的量子反常霍尔/超导马赫-曾德尔干涉仪中追求作为涡旋数的量子相干振荡，以确定在具有科尔比诺几何的量子反常霍尔/超导器件中马约拉纳费米子的存在和这种马约拉纳费米子的非阿贝尔编织。本项目还研究了在均匀磁化和高陈数量子反常霍尔/超导异质结中的多个手征Majorana费米子作用下，外电场诱导的拓扑超导相在量子反常霍尔/超导杂化结构中的输运特征。该项目的成功将导致对拓扑超导相微观机制的重大新理解，并具有深远的技术影响，特别是对拓扑量子计算机的开发。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Non-technical abstract:The rapidly increasing need for high computing power requires a drastic paradigm shift away from traditional computers based on silicon transistors. A quantum computer, which makes use of quantum physics to store information and execute calculations is expected to be vastly more efficient and hence more powerful than a traditional computer. An attractive scheme towards quantum computation involves a newly-discovered class of materials, called topological insulators, where the interior is insulating but the surface is electrically conducting. Magnetic elements can be incorporated into such a topological insulator sample to achieve a curious phenomenon called quantum anomalous Hall effect. In this state the surface electrons are confined to the edges of the sample and flow without resistance. It has been predicted that quantum computation can be achieved in a device where this resistance-free edge current of the quantum anomalous Hall insulator is utilized. This project aims to test this prediction. Active education and outreach programs for graduate and undergraduate students, K-12 students and teachers, and the general public are integral part of planned work.Technical Abstract:The coupling of the spin-polarized dissipation-free edge state of a quantum anomalous Hall insulator and a conventional superconductor has been predicted to harbor a topological superconductivity phase that supports gapless Majorana fermion excitation at surfaces or edges of the sample. Topological superconductivity can reveal transformative new physics, such as non-Abelian statistics, and enable new architectures for topological quantum computation. In this project, the principal investigator pursues the quantum coherent oscillations as a function of vortices number in a micrometer-sized quantum anomalous Hall/superconductor Mach-Zehnder interferometer to ascertain the existence of the Majorana fermion and the non-Abelian braiding of such Majorana fermions in a quantum anomalous Hall/superconductor device with Corbino geometry. This project also explores the transport signatures of external electrical field induced topological superconductivity phase in quantum anomalous Hall/superconductor hybrid structures under homogenous magnetization and multiple chiral Majorana fermions in high-Chern-number quantum anomalous Hall/superconductor heterostructures. The success of the project will lead to significant new understanding of the microscopic mechanisms of topological superconductivity phase and carries far-reaching technological implications especially for the development of the topological quantum computer.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.