Vortex pinning is a crucial factor that determines the critical current of practical superconductors and enables their diverse applications. However, the underlying mechanism of vortex pinning has long been elusive, lacking a clear microscopic explanation. Here, using high-resolution scanning tunneling microscopy, we studied single vortex pinning induced by point defect in layered FeSe-based superconductors. We found the defect-vortex interaction drives low-energy vortex bound states away from 𝐸F, creating a “mini” gap that effectively lowers the system energy and enhances pinning. By measuring the local density of states, we directly obtained the elementary pinning energy and estimated the pinning force via the spatial gradient of pinning energy. The results are consistent with bulk critical current measurement. Furthermore, we showed that a general microscopic quantum model incorporating defect-vortex interaction can naturally capture our observation. It suggests that the local pairing near pinned vortex core is actually enhanced compared to unpinned vortex, which is beyond the traditional understanding that nonsuperconducting regions pin vortices. Our study thus unveils a general microscopic mechanism of vortex pinning in superconductors and provides insights for enhancing the critical current of practical superconductors.

中文翻译：

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揭示超导体中基本涡旋固定的微观机制


涡流针刺是决定实际超导体临界电流并实现其多样化应用的关键因素。然而，涡旋固定的潜在机制长期以来一直难以捉摸，缺乏明确的微观解释。在这里，我们使用高分辨率扫描隧道显微镜研究了层状 FeSe 基超导体中点缺陷诱导的单涡旋钉扎。我们发现缺陷-涡旋相互作用将低能涡旋结合态从 EF 中驱赶出去，从而形成一个“迷你”间隙，从而有效地降低系统能量并增强固定。通过测量局部状态密度，我们直接获得了基本固定能量，并通过固定能量的空间梯度估计了固定力。结果与体临界电流测量一致。此外，我们表明，结合缺陷-涡旋相互作用的通用微观量子模型可以自然地捕捉我们的观察结果。这表明，与非固定涡旋相比，固定涡旋核心附近的局部配对实际上得到了增强，这超出了非超导区域固定涡旋的传统理解。因此，我们的研究揭示了超导体中涡旋固定的一般微观机制，并为增强实际超导体的临界电流提供了见解。