At an interface between a topological insulator (TI) and a conventional superconductor (SC), superconductivity has been predicted to change dramatically and exhibit novel correlations. In particular, the induced superconductivity by an $s$-wave SC in a TI can develop an order parameter with a $p$-wave component. Here we present experimental evidence for an unexpected proximity-induced novel superconducting state in a thin layer of the prototypical TI, ${\mathrm{Bi}}_2{\mathrm{Se}}_3$ proximity coupled to Nb. From depth-resolved magnetic field measurements below the superconducting transition temperature of Nb, we observe a local enhancement of the magnetic field in ${\mathrm{Bi}}_2{\mathrm{Se}}_3$ that exceeds the externally applied field, thus supporting the existence of an intrinsic paramagnetic Meissner effect arising from an odd-frequency superconducting state. Our experimental results are complemented by theoretical calculations supporting the appearance of such a component at the interface which extends into the TI. This state is topologically distinct from the conventional Bardeen-Cooper-Schrieffer state it originates from. To the best of our knowledge, these findings present a first observation of bulk odd-frequency superconductivity in a TI. We thus reaffirm the potential of the TI-SC interface as a versatile platform to produce novel superconducting states.

中文翻译：

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拓扑绝缘子中的邻近感应奇数频率超导。

在拓扑绝缘体（TI）和常规超导体（SC）之间的界面处，已预测超导性会发生巨大变化并表现出新颖的相关性。特别是，通过$s$TI中的波SC可以利用 $p$波分量。在这里，我们提供了在原型TI薄层中出乎意料的邻近感应新型超导状态的实验证据，${双}_2{硒}_3$邻近耦合到Nb。从低于Nb超导转变温度的深度解析磁场测量中，我们观察到磁场的局部增强${双}_2{硒}_3$它超出了外部施加的磁场，因此支持了由奇频超导状态引起的固有顺磁迈斯纳效应的存在。我们的实验结果得到了理论计算的补充，这些计算支持了此类组件在延伸到TI的界面上的外观。该状态在拓扑上不同于其起源的常规Bardeen-Cooper-Schrieffer状态。据我们所知，这些发现首次显示了TI中体积奇数超导性。因此，我们重申TI-SC接口作为产生新颖超导状态的通用平台的潜力。