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 $s$-wave and $d$-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.

中文翻译：

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非常规超导体中的原子线缺陷和拓扑超导

拓扑超导体（TSC）是相关的量子态，同时具有对角远距离阶和非平凡的拓扑不变量。它们产生无间隙或零能量的边界激发，包括马约拉那零模和手性马约拉那边沿态，其拓扑受保护的相干性是容错量子计算必不可少的。候选TSC在自然界中非常罕见。在这里，我们提出了一条通往自然嵌入的量子结构（例如非常规自旋单重原子中的原子线缺陷）中的准一维（1D）TSC的新颖途径。$s$波和 $d$波超导体。我们表明，由于缺少原子而导致的反转对称破坏和电荷转移导致占据了初始杂质带，并且遍历线缺陷的相邻电子的混合奇偶自旋-单重态和-三重态库珀配对。非平凡的拓扑不变量出现并占据了参数空间的很大一部分，包括由于施加磁场或缺陷感应的磁场而造成的时间反转对称破坏Zeeman耦合，从而在不同的拓扑类别中创建了TSC，并且两端都具有鲁棒的Majorana零模式。线路缺陷。除了为最近发现单层Fe（Te，Se）超导体的原子线缺陷两端的零能束缚态提供新的机制外，