拓扑绝缘体/超导体异质结中的近邻效应

Proximity effect in topological insulator/superconductor heterostructure

拓扑超导体自身具有对量子退相干天然的免疫性以及可编织性,这使得它在现代量子计算领域中受到了越来越多的重视,并且成为了下一代计算技术中最有希望的候选者之一。由于拓扑超导态在固有拓扑超导体中相当罕见,因此,当前大部分实验上的工作主要集中在由s波超导体与拓扑绝缘体之间通过近邻效应所诱导的拓扑超导体上。本论文中,我们回顾了基于拓扑绝缘体/超导体异质结的拓扑超导体的研究进展。在理论上,Fu和Kane提出,通过近邻效应将s波超导体的能隙引入到拓扑绝缘体,可以诱导出拓扑超导电性。在实验上,我们也回顾了一些不同体系中的拓扑超导近邻效应的研究进展。文章的第一部分,我们介绍了一些异质结,包括:三维拓扑绝缘体Bi_(2)Se_(3)和Bi_(2)Se_(3)与s波超导体NbSe_(2)以及d波超导体Bi_(2)Sr_(2)CaCu_(2)O_(8)+δ的异质结,拓扑绝缘体Sn_(1−x)Pb_(x)Te与Pb的异质结,二维拓扑绝缘体WTe_(2)与NbSe_(2)的异质结。此外,还介绍了TiBiSe_(2)在Pb上的拓扑绝缘近邻效应。另一部分中,我们对基于拓扑绝缘体的约瑟夫森结进行了回顾,包括著名的基于Fu-Kane体系的拓扑绝缘体约瑟夫森结,以及基于约瑟夫森结的超导量子干涉器件。

Topological superconductors have attracted increasing attentions for the purpose of the quantum computation,because the character of supporting topological qubits are immune to quantum decoherence and can be manipulated by braiding operation.Since the topological superconducting state is rather rare in the intrinsic topological superconductors,most of experimental efforts focus on inducing topological superconductors by the proximity effect in superconductor(SC)/topological insulator(TI)heterostructures.Fu and Kane have theoretically proposed that the topological superconductivity can be obtained by inducing an s-wave superconducting gap into TIs.After that,a lot of experimental progress has been made in different systems.In the first part of this review,we introduce the heterostructure of threedimensional(3D)TI Bi_(2)Se_(3)and Bi_(2)Te_(3)on s-wave SC NbSe_(2)and d-wave SC Bi_(2)Sr_(2)CaCu_(2)O_(8)+δ,topological crystalline insulator Sn_(1−x)Pb_(x)Te on Pb,two-dimensional(2D)TI WTe_(2)on NbSe_(2),and TiBiSe_(2)on Pb.In the second part,the TI-based Josephson junctions are reviewed by introducing various experiments,including the Josephson junctions with TI barrier layers based on the Fu-Kane mode,and the superconducting quantum interference devices by TI based Josephson junctions.