拓扑绝缘体与超导体异质结中马约拉纳态的实验研究

Since the discovery of topological insulator (TI), it has attracted a lot of interests. And the topological superconductor is becoming a hot research topic in recent years since it is the platform for the Majorana fermions. It has been found that the topological superconducting state can be induced by the superconducting proximity effect in TI theoretically and experimentally. The Majorana bound state and Majorana edge state could be realized in this two dimensional topological superconducting state. Although significant progress has been made in the search of Majorana state, there is still a lot of works need to be done urgently in the experiment, especially the chiral Majorana edge states. It has been predicted that the chiral Majorana edge states can be realized by superconducting proximity effect in the quantum anomalous Hall state or the quantum Hall state of the topological surface state. The first method based on the quantum anomalous Hall state has be realized. But the other method, which is based on the quantum Hall effect of the topological surface state, has not been studied yet. In our previous studies, we have achieved the well-developed quantum Hall effect of topological surface state by optimizing the topological insulator. In this project, we plane to fabricate the heterostructure between TI and superconductors, and optimize the materials and structures for achieving the superconducting proximity effect. Then we will study the novel transport phenomena and the Majorana states in the quantum Hall region.

拓扑绝缘体自发现以来，就受到广泛关注。而拓扑超导由于可以实现马约拉纳态，成为了近年来的热点。理论和实验研究表明，通过超导体对拓扑绝缘体的近邻效应可以在其界面诱导出拓扑超导态。在这样的二维拓扑超导体系中，可以实现马约拉纳束缚态和马约拉纳边态。虽然实验对马约拉纳态的探索上已经有了重大进展，但仍有很多工作亟待开展，尤其是对手性马约拉纳边态的研究。理论预言在超导近邻的量子反常霍尔绝缘体中或者是拓扑表面态的量子霍尔态中可以实现手性马约拉纳边态。实验上已经证实了前者；但第二种实现手性马约拉纳边态的方案（即在拓扑表面态的量子霍尔平台区近邻超导体）还未被研究。前期我们已经通过优化拓扑绝缘体，得到了完好的拓扑表面态的量子霍尔效应。本项目计划通过制备拓扑绝缘体与超导体的异质结，并且不断优化其材料与结构，得到完好的超导近邻效应；然后探索新奇的输运现象，尤其是手性马约拉纳边态。

拓扑绝缘体是近年来广受关注的新兴量子材料，其在未来的电子元器件等方面具有一定的应用前景。其中，拓扑表面态的量子输运尤为重要。本项目以拓扑绝缘体和磁性拓扑绝缘体的介观器件及其异质结为研究对象，主要探索其中新奇的量子输运现象及器件新物理。申请人围绕本项目的任务开展工作，在拓扑绝缘体体系中的量子霍尔态及其调控等方面展开研究，做出了一系列富有特色的创新性成果。在本征磁性拓扑绝缘体器件中实现了陈绝缘态，观测到了栅压调控的反常霍尔翻转，并在其磁性异质结中实现了大的交换偏置效应；通过光照调控了拓扑绝缘体中的量子霍尔态。基于以上这些工作成果，发表了多篇研究论文。