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    20 June 2021, Volume 41 Issue 3 Previous Issue    Next Issue

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    Proximity effect in topological insulator/superconductor heterostructure
    He Jia-Dian, Ding Yi-Fan, Teng Bo-Lun, Dong Peng, Li Yi-Fei, Zhang Yi-Wen, Wu Yue-Shen, Wang Jing-Hui, Zhou Xiang, Wang Zhi, Li Jun
    2021, 41 (3):  113-135.  doi: 10.13725/j.cnki.pip.2021.03.001
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    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 Bi2Se3 and Bi2Te3 on s-wave SC NbSe2 and d-wave SC Bi2Sr2CaCu2O8+δ, topological crystalline insulator Sn1−xPbxTe on Pb, two-dimensional (2D) TI WTe2 on NbSe2, and TiBiSe2 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.

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    Magnetic exchange induced Weyl states in the antiferromagnetic semimetals EuCd2Pn2 (Pn = As, Sb)
    Su Hao , Chen Lei-Ming, Xia Wei, Guo Yan-Feng
    2021, 41 (3):  136-156.  doi: 10.13725/j.cnki.pip.2021.03.002
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    Three-dimensional (3D) topological semimetals (TSMs) have arrested special attentions as 3D analogues to graphene. The TSMs, for example, the Dirac and Weyl semimetals, show an array of intriguing physical properties arising from the electronic band structure topology, which have therefore been under immense investigations. Most of the known TSMs are nonmagnetic, whereas the magnetic TSMs are very few and remain less investigated. The interplay between magnetism and nontrivial topological states can result in exceptional physical properties, such as anomalous or even quantum anomalous Hall effect. In some TSMs with peculiar magnetic structures, the magnetic exchange could be tuned by application of an external magnetic field, which consequently can affect the topological properties. We review herein the family of antiferromagnetic semimetals EuCd2Pn2 (Pn = As, Sb) which exhibit topological phase transitions induced by an external magnetic field through tuning the spin structures and hence the structure symmetries that are protecting the topological states. Besides, we will also briefly review several other related materials including the GdPtBi and MnBi2Te4. The herein discussed magnetism induced topological phase transition provides potential use in novel topological devices since the topological states could be conveniently controlled by external magnetic field. Furthermore, it also contributes important clues toward understanding the intimate relation between magnetism and topological states, which are instructive for designing new magnetic topological phases. At the end of this review, we also give a short perspective for the development of the magnetic TSMs.

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