Superconducting metal dichalcogenides (MDCs) present several similarities to the other layered superconductors like cuprates. The superconductivity in atomically thin MDCs has been demonstrated by recent experiments, however, the investigation of the superconductivity intertwined with other orders are scarce. Investigating the pseudogap in atomic layers of MDCs may help to understand the superconducting mechanism for these true two-dimensional (2D) superconducting systems. Herein we report a pseudogap opening in the tunneling spectra of thin layers of SnSe₂ epitaxially grown on highly oriented pyrolytic graphite (HOPG) with scanning tunneling microscopy/spectroscopy (STM/STS). A significant V-shaped pseudogap was observed to open near the Fermi level (E_F) in the STS. And at elevated temperatures, the gap gradually evolves to a shallow dip. Our experimental observations provide direct evidence of a pseudogap state in the electron-doped SnSe₂ atomic layers on the HOPG surface, which may stimulate further exploration of the mechanism of superconductivity at 2D limit in MDCs.

中文翻译：

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石墨上生长的SnSe 2原子层中假间隙的观察

超导金属二硫化碳（MDC）与其他层状超导体（如铜酸盐）存在一些相似之处。原子薄MDCs中的超导性已经通过最近的实验得到了证明，但是，与其他顺序交织在一起的超导性研究却很少。研究MDC原子层中的伪间隙可能有助于了解这些真正的二维（2D）超导系统的超导机制。本文中，我们通过扫描隧道显微镜/光谱学（STM / STS）在高取向热解石墨（HOPG）上外延生长的SnSe ₂薄层的隧道光谱中报告了伪间隙开口。在费米能级附近（E _F）。并且在升高的温度下，间隙逐渐演变为浅倾角。我们的实验观察结果提供了HOPG表面电子掺杂SnSe ₂原子层中伪间隙状态的直接证据，这可能会刺激人们进一步探索MDC中2D极限的超导机理。