Vortices in topological superconductors are predicted to host Majorana bound states (MBSs) as exotic quasiparticles. In recent experiments, the spatially non-split zero-energy vortex bound state in topological superconductors has been regarded as an essential spectroscopic signature for the observation of MBSs. Here, we report the observation of anisotropic non-split zero-energy vortex bound states in a conventional elemental superconductor with a topologically trivial band structure using scanning tunneling microscopy and spectroscopy. The experimental results, corroborated by quasi-classical theoretical calculations, indicate that the non-split states directly reflect the quasiparticle trajectories governed by the surface electronic structure. Our study implies that non-split zero-energy states are not a conclusive signature of MBSs in vortex cores, in particular for superconducting systems not being in the quantum limit, stimulating a revision of the current understanding of such states.

中文翻译：

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传统超导体中的各向异性非分裂零能涡流束缚态

拓扑超导体中的涡流预计将作为奇异准粒子承载马约拉纳束缚态 (MBS)。在最近的实验中，拓扑超导体中的空间非分裂零能量涡流束缚态已被视为观察 MBS 的基本光谱特征。在这里，我们报告了使用扫描隧道显微镜和光谱学在具有拓扑微不足道的带结构的传统元素超导体中观察到的各向异性非分裂零能量涡流束缚态。经准经典理论计算证实的实验结果表明，非分裂态直接反映了受表面电子结构支配的准粒子轨迹。