Interfacial magnetism in topological insulator heterostructures

项目简介：约5%的电力在传输过程中被浪费，而电器将很大一部分电力转化为不需要的热量。该项目旨在研究一类具有克服能量耗散的潜力的新材料。三维拓扑绝缘体(“Tis”)具有绝缘体但导电表面，这些表面受到拓扑保护--这是大的自旋-轨道耦合和时间反转对称性的结果。在磁性掺杂的TiS中，量子反常霍尔效应(QAHE)于2013年被预言并得到实验证实。类似于几十年前观察到的量子霍尔效应(“QHE”)，手性的无耗散输运发生在样品的边缘。由于需要较高的磁场和较低的温度，QHE很难实现。QAHE的要求要低得多，对主体材料的某些磁性和拓扑性质的存在感到满意。挑战是找到在技术上可行的温度下具有这些性能的合适材料，最好是在室温下。该项目的目标是利用一种综合的、同步加速器和基于中子的多工具方法，提供关于拓扑磁性材料的开创性实验结果，特别是近距离耦合到原子力显微镜。它的目标是实现在高温下实现QAHE的一大飞跃，这将结束对昂贵的冷却和外部磁场的需求，并将是节能电子设备创新的突破性进展。我们将结合拓扑绝缘体和反铁磁体(AFS)来诱导TIS中的磁性有序，并实现QAHE所需的Dirac表面态带隙结构的间隙开放，并探索将温度提高到低温以上的可能性。与铁磁体相比，原子力显微镜具有许多优点，如较高的磁有序温度和较强的邻近效应。此外，由于AF的补偿自旋结构，不会产生杂散场，便于TI的磁性表征，从而支持材料的优化。本项目的意义是通过AF-TI邻近耦合将QAHE的运行扩展到更高的温度。我们设想利用钻石和ISIS的结合的独特能力，并提出一个多方法研究磁性(XAS/XMCD/XMLD，XPEEM，PNR)和电子性质(HAXPES，运输)。该项目是与钻石光源(Dirk Backes博士)和ISIS/STFC(肖恩·朗里奇教授)的联合项目。该项目与EPSRC的研究领域“凝聚态物质：磁性和磁性材料”和“自旋电子学”相一致。

Project description:About 5% of electricity is wasted during transmission, while electric appliances convert a large fraction of the electricity into unwanted heat. This project aims at investigating a new class of materials with the potential to overcome dissipation of energy. Three-dimensional topological insulators ("Tis") have an insulating bulk but conductive surfaces, which are topologically protected - a consequence of large spin-orbit coupling and time reversal symmetry. In magnetically doped TIs, the quantum anomalous Hall effect ("QAHE") was predicted and experimentally confirmed in 2013. Similar to the quantum Hall effect ("QHE"), which was observed several decades earlier, chiral, dissipationless transport takes place at the edges of the sample. The QHE is difficult to realise since high magnetic fields and low temperatures are required. The QAHE is much less demanding, being satisfied with the presence of certain magnetic and topological properties of the host materials. The challenge is to find suitable materials which have these properties at technically feasible temperatures, ideally at room temperature.The Project will aim to deliver ground-breaking experimental results on topological magnetic materials, in particular TIs proximity-coupled to AFs, using an integrated, synchrotron- and neutron-based multi-tool approach. It aims at achieving a big leap forward towards the realisation of the QAHE at high temperatures, which will put an end to the need for expensive cooling and external magnetic fields and will be ground-breaking for innovations in energy-efficient electronic devices. We will combine topological insulators with antiferromagnets (AFs) to induce magnetic order in the TIs and achieve a gap-opening in the band structure of the Dirac surface states - requirements for the QAHE and explore the potential for increasing the temperature beyond cryogenic temperatures. AFs benefit from many advantages compared to ferromagnets, such as a higher magnetic ordering temperature and a stronger proximity effect. Furthermore, no magnetic stray fields are produced due to the compensated spin structure of the AF, facilitating the magnetic characterisation of the TI and consequently supporting the optimisation of the materials.The significance of this Project is to expand the operation of the QAHE towards even higher temperatures by AF-TI proximity coupling. We envision to make use of the combined unique capabilities of Diamond and ISIS, and propose a multi-method study of the magnetic properties (XAS/XMCD/XMLD, XPEEM, PNR) and electronic properties (HAXPES, transport).This project is a joint project with the Diamond Light Source (Dr Dirk Backes) and ISIS/STFC (Prof Sean Langridge).This project aligns with EPSRC's research areas "Condensed Matter: Magnetism and Magnetic Materials" and "Spintronics".