用于超快泵浦-探测光谱的改进型低温扫描隧道显微镜
Modified Low-Temperature Scanning Tunneling Microscope for Ultrafast Pump-Probe Spectroscopy
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中文总结 AI 辅助
该研究通过最小化改动Besocke型低温STM，实现太赫兹脉冲高效耦合，在6 K以下保持原子级分辨率，并成功探测MoS₂中的点缺陷，为超快泵浦-探测光谱提供新方案。
中文摘要 AI 辅助
将扫描隧道显微镜（STM）与太赫兹脉冲相结合（THz-STM），能够以原子级空间分辨率和亚皮秒时间分辨率探测声子、自旋和电荷载流子的超快动力学。然而，将太赫兹辐射耦合到低温STM结中面临一些技术挑战，因为这需要光学通路进行激光照射，同时保持结的稳定性。我们没有设计一个全新的、在超高真空腔内具有定制光学通路和光学元件的STM头，而是对Besocke“甲虫”型STM进行了最小程度的改动，仅修改了低温辐射屏蔽。尽管存在给定的几何条件，我们仍实现了太赫兹和光学脉冲到STM结的高效耦合，同时将温度保持在6 K以下。我们在一个独立的激光桌上设计了光学装置，从飞秒激光脉冲开始，用于在LiNbO$_3$晶体中产生太赫兹脉冲。我们展示了所获得的太赫兹脉冲形状，并通过互相关测量确定了有效时间分辨率。我们进一步通过测量在Au(111)上生长的单层二硫化钼（MoS$_2$）的太赫兹诱导隧穿电流，证明了改进型STM的稳定性能。所得的电流图解析出原子级对比度，揭示了一个点缺陷。这些测量证实了高效的太赫兹耦合以及具有原子分辨率的稳定低温STM运行。
英文摘要
Combining scanning tunneling microscopy (STM) with terahertz pulses (THz-STM) enables ultrafast dynamics of phonons, spins, and charge carriers to be probed with atomic-scale spatial and sub-picosecond temporal resolution. However, coupling THz radiation into a low-temperature STM junction presents some technical challenges as it requires optical access for laser illumination while maintaining junction stability. Instead of designing a completely new STM head with customized optical access and optics within the ultra-high vacuum chamber, we modified a Besocke "Beetle" style STM with minimal changes of the cryogenic radiation shields. Despite the given geometrical conditions, we achieved efficient coupling of THz and optical pulses to the STM junction while maintaining temperatures below 6 K. We designed the optical setup on a separate laser table, starting with femtosecond laser pulses that are used to generate THz pulses in a LiNbO$_3$ crystal. We show the obtained THz pulse shapes and determine the effective time resolution using cross-correlation measurements. We further demonstrate the stable performance of the modified STM by measuring THz-induced tunneling currents from monolayer molybdenum disulfide (MoS$_2$) grown on Au(111). The resulting current maps resolve atomic-scale contrast revealing a point defect. The measurements confirm efficient THz coupling and stable low-temperature STM operation with atomic resolution.
发表机构
- Freie Universität Berlin（柏林自由大学）
机构由 AI 辅助整理，请以论文原文为准。
