Non-trivial topology and unconventional pairing are two central guiding principles in the contemporary search for and analysis of superconducting materials and heterostructure compounds. Previously, a topological superconductor has been predominantly conceived to result from a topologically non-trivial band subject to intrinsic or external superconducting proximity effect. Here, we propose a new class of topological superconductors which are uniquely induced by unconventional pairing. They exhibit a boundary-obstructed higher-order topological character and, depending on their dimensionality, feature unprecedently robust Majorana bound states or hinge modes protected by chiral symmetry. We predict the 112-family of iron pnictides, such as Ca${}_{1-x}$La${}_x$FeAs${}_2$, to be a highly suited material candidate for our proposal, which can be tested by edge spectroscopy. Because of the boundary-obstruction, the topologically non-trivial feature of the 112 pnictides does not reveal itself for a bulk-only torus band analysis without boundaries, and as such had evaded previous investigations. Our proposal not only opens a new arena for highly stable Majorana modes in high-temperature superconductors, but also provides the smoking gun evidence for extended s-wave order in the iron pnictides.

中文翻译：

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铁素化物的边界受阻拓扑高Tc超导性

非平凡的拓扑结构和非常规的配对是当代寻找和分析超导材料和异质结构化合物的两个主要指导原则。以前，主要认为拓扑超导体是由受到固有或外部超导邻近效应影响的拓扑非平凡带产生的。在这里，我们提出了一类新的拓扑超导体，它是由非常规配对独特地诱发的。它们表现出边界受阻的高阶拓扑特征，并且根据其维数，具有前所未有的鲁棒的马约拉邦键合态或受手性对称性保护的铰链模式。我们预测了铁素族的112个家族，例如Ca${}_{\mathrm{1个}-X}$啦${}_X$砷化铁${}_2$，成为我们建议的非常合适的材料候选者，可以通过边缘光谱法对其进行测试。由于边界的阻碍，对于没有边界的仅限本体的圆环带分析，这112个杀虫剂的拓扑学上很重要的特征并未显示出来，因此避免了以前的研究。我们的建议不仅为高温超导体中高度稳定的Majorana模式开辟了一个新的舞台，而且还为吸烟枪提供了铁素体中s波序延长的证据。