超导/拓扑绝缘体复合结构界面超导近邻效应研究

The hybrid structure of superconductors and topological insulators has attracted great attention in past few years, as it provides an ideal platform for the investigation of superconducting proximity effect (SPE) and the exploration and manipulation of the Majorana bound states resided in the interfaces of the superconductors and topological insulators hybrid structures. In this project, we propose to experimentally study the SPE in hybrid structures of BixSb2-xTeySe3-y (BSTS) and s-wave superconductor NbSe2. The BSTS single crystals with a high mobility and a low carrier density will be grown by chemical vapor transport (CVT) method. The hybrid structures with transparent interfaces will be fabricated by mechanical transfer of exfoliated layered NbSe2 flakes onto exfoliated BSTS flakes. We aim to carry out magnetotransport investigation of SPE in NbSe2/BSTS hybrid structures and to explore different roles of topological surface states and bulk states of BSTS by tuning the Fermi level using gate voltages, which have not been envisioned. The fulfillment of this project will greatly advance our understanding of the interactions of topological surface states with the superconductor, and the successful outcome of this project will pave the way for future applications in topological quantum computation.

超导/拓扑绝缘体复合结构为研究界面超导近邻效应，以及探测和调控由此诱导产生的界面马约拉纳束缚态提供一个很好的研究平台，从而引起广泛关注。本项目拟采用化学气相转移方法制备费米能级连续可调的四元拓扑绝缘体Bi2-xSbxTe3-ySey (BSTS)单晶材料，并在此基础上构筑界面接触良好的超导/拓扑绝缘体（NbSe2/BSTS）复合结构。表征复合结构界面的超导近邻效应的电输运特性，重点关注拓扑绝缘体表面态和体态的超导近邻效应的异同。除此之外，探测界面超导近邻效应诱导产生的拓扑超导体中马约拉纳束缚态，并进一步实现对马约拉纳束缚态的调控。我们希望通过本项目的开展，能够揭示超导/拓扑绝缘体复合结构界面超导近邻效应的微观物理机制，在探测和调控界面的马约拉纳束缚态方面取得一些实验进展，为拓扑量子计算的发展提供有用参考。

在本项目的支持下，我们围绕低维拓扑材料磁电输运物性调控和异质结界面超导近邻效应开展了系统的研究。取得的主要创新成果包括：1)成功制备了四元拓扑绝缘体BiSbTeSe2(BSTS)单晶，实现拓扑表面态和体态的磁电输运特性的调控；构筑BiSbTeSe2与s-波超导NbSe2异质复合结构，在低温下观测到微分电导峰；2)构筑了基于s-波超导的异质复合结构(2H-TaS2/NbSe2)，揭示了界面超导近邻效应对超导特性的增强作用；3)获得大尺寸的新型拓扑材料，外尔半导体Te薄片，并探究了其可能的器件应用；4)通过非磁性硫族元素取代以及外加磁场，实现了二维范德华层状反铁磁材料的低温磁性的调控。在该项目执行期间，共正式发表SCI论文6篇，已接收发表SCI论文2篇，包括1篇 Phys. Rev. B，3篇Appl. Phys. Lett.，1篇Nanoscale等。