Atomic Line Defects and Topological Superconductivity in Unconventional Superconductors
Atomic Line Defects and Topological Superconductivity in Unconventional Superconductors
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非常规超导体中的原子线缺陷和拓扑超导性
DOI：
10.1103/physrevx.11.011041
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发表时间：
2021
影响因子：
12.5
通讯作者：
Wang Ziqiang
中科院分区：
文献类型：
--
作者：
Zhang Yi;Jiang Kun;Zhang Fuchun;Wang Jian;Wang Ziqiang
拓扑超导体是同时具有非对角长程有序和非平凡拓扑不变量的关联量子态。它们产生无隙或零能量边界激发，包括马约拉纳零模式和手性马约拉纳边缘状态，具有容错量子计算所必需的拓扑保护相位相干性。候选TSC在自然界中非常罕见。在这里，我们提出了一种新的路线，对紧急准一维（1D）TSC在自然嵌入的量子结构，如原子线缺陷在非常规的自旋单重波和波超导体。我们发现，反转对称性破缺和电荷转移，由于丢失的原子导致占领的初期杂质带和混合宇称自旋单重态和三重态库珀配对的相邻电子穿越线缺陷。非平凡的拓扑不变量的出现，并占据了很大一部分的参数空间，包括时间反演的破环塞曼耦合由于施加的磁场或缺陷引起的磁性，创建TSC在不同的拓扑类与强大的马约拉纳零模式的两端线缺陷。除了为最近在单层Fe（Te，Se）超导体中原子线缺陷两端发现的零能量束缚态提供一种新的机制外，这些发现还为在具有大配对能隙和高转变温度的非常规超导体中使用嵌入式量子结构实现最简单和最稳健的1D TSC的新材料铺平了道路。
Topological superconductors (TSCs) are correlated quantum states with simultaneous off-diagonal long-range order and nontrivial topological invariants. They produce gapless or zero-energy boundary excitations, including Majorana zero modes and chiral Majorana edge states with topologically protected phase coherence essential for fault-tolerant quantum computing. Candidate TSCs are very rare in nature. Here, we propose a novel route toward emergent quasi-one-dimensional (1D) TSCs in naturally embedded quantum structures such as atomic line defects in unconventional spin-singlet-wave and-wave superconductors. We show that inversion symmetry breaking and charge transfer due to the missing atoms lead to the occupation of incipient impurity bands and mixed-parity spin-singlet and -triplet Cooper pairing of neighboring electrons traversing the line defect. Nontrivial topological invariants arise and occupy a large part of the parameter space, including the time-reversal symmetry-breaking Zeeman coupling due to applied magnetic field or defect-induced magnetism, creating TSCs in different topological classes with robust Majorana zero modes at both ends of the line defect. Beyond providing a novel mechanism for the recent discovery of zero-energy bound states at both ends of an atomic line defect in monolayer Fe(Te,Se) superconductors, the findings pave the way for new material realizations of the simplest and most robust 1D TSCs using embedded quantum structures in unconventional superconductors with large pairing energy gaps and high transition temperatures.