EAGER: BRAIDING: Majorana modes in monolayer topological insulator WTe2

摘要：寻找量子计算的替代路径在这个时候是至关重要的，目前的方法面临许多障碍。最大的问题是量子比特的退相干性，这意味着量子信息内容会随着时间呈指数级衰减。原则上，退相干可以使用“拓扑保护”来避免。唯一现实的已知拓扑保护方案是基于从所谓的马约拉纳模式（Majorana mode）中创建量子位，这种模式是发生在某些类型量子线末端的特殊状态。制造马约拉纳的一种方法是使用存在于拓扑绝缘体边缘的特殊量子线。PI是一位实验学家，最近发现了第一个天然单层二维（2D）拓扑绝缘体，这表明在二维材料中创建和操作Majoranas的可能性。副pi是拓扑现象的理论家和专家；在这个项目中，他们合作寻找在这个系统中创建和检测Majoranas的最简单方法。这项工作支持研究生进行理论和实验相结合的专题跨学科工作，可以想象，这可能会产生下一次信息革命。该项目在华盛顿大学和当地工业界（包括微软）之间架起了一座桥梁，华盛顿大学在二维材料方面的研究工作处于领先地位，而当地工业界（包括微软）正在大力投资量子计算机的应用。技术：该项目旨在建立二维材料平台的可行性，以创建可用于拓扑量子处理的Majorana零模式。该团队采用单层WTe2作为二维拓扑绝缘体，结合二维超导体（NbSe2或FeSe）和二维磁铁（CrI3或CrBr3）。这些材料与电触点和隧道势垒一起堆叠成范德华异质结构。在这三种材料相遇的地方，马约拉纳模式可能出现在低温下，可以通过隧道测量来探测。与其他Majorana系统相比，该2D平台具有优势，包括不需要磁场来产生螺旋模式，并且可以避免化学势的微妙调整。涉及的多电子和拓扑物理的复杂性，以及系统的新颖性，要求实验和理论之间的密切合作。具体目标是诱导和理解WTe2螺旋边缘的超导邻近间隙，并设计和测试最简单的二维异质结构器件，其中可能发生和检测到Majoranas。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Nontechnical Abstract: Finding alternative paths to quantum computing is paramount at this time, and current approaches face many hurdles. The biggest is decoherence of the qubits, meaning that the quantum information content decays exponentially with time. In principle, decoherence can be avoided using "topological protection". The only realistic known scheme for topological protection is based on creating the qubits from so-called Majorana modes, which are peculiar states that occur at the ends of certain types of quantum wires. One way to make Majoranas is using the special quantum wire that exists at the edge of a topological insulator. The PI, an experimentalist, recently discovered the first natural monolayer two-dimensional (2D) topological insulator, suggesting the possibility to create and manipulate Majoranas in 2D materials. The co-PI is a theorist and expert on topological phenomena; in this project they collaborate to find the simplest way to create and detect Majoranas in this system. The work supports graduate students in topical interdisciplinary work where theory and experiment go hand in hand, and which could conceivably give birth to the next information revolution. The project forms a bridge between the University of Washington, which has a leading research effort in 2D materials, and local industry (including Microsoft) which is investing heavily in applications of quantum computers.Technical: This project aims to establish the viability of the 2D materials platform for creating Majorana zero modes that could be used for topological quantum processing. The team employs monolayer WTe2 as a 2D topological insulator, combined with a 2D superconductor (NbSe2 or FeSe) and a 2D magnet (CrI3 or CrBr3). These materials are stacked into a van der Waals heterostructure along with electrical contacts and tunnel barriers. At the point where the three materials meet a Majorana mode may appear at low temperatures and can be probed by tunneling measurements. This 2D platform offers advantages compared with other Majorana systems including that no magnetic field is required to produce the helical mode, and the possibility to avoid delicate tuning of the chemical potential. The complexity of the many-electron and topological physics involved, and the novelty of the system, calls for close cooperation between experiment and theory. Specific goals are to induce and understand a superconducting proximity gap in the helical edge of WTe2, and to design and test the simplest 2D possible heterostructure devices in which Majoranas may occur and be detected.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.