Control of Surface Plasmon Propagation and Terahertz Near-Field Waveforms in a Scanning Tunneling Microscope

IF 9.6 1区材料科学 Q1 CHEMISTRY, MULTIDISCIPLINARY

Nano Letters Pub Date : 2024-11-21 DOI:10.1021/acs.nanolett.4c04152

Shaoxiang Sheng, Li Chen, Johannes Schust, Kurt Lichtenberg, Mohamad Abdo, Felix Huber, Susanne Baumann, Sebastian Loth

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Abstract

Coupling subcycle THz pulses to a scanning tunneling microscope (STM) enables ultrafast spectroscopy at the atomic scale. This technique critically depends on the shape of the THz near-field waveform in the tunnel junction. We characterize the THz electric field waveform in the STM junction by electro-optic sampling of tip-scattered THz light (s-EOS) and pulse correlation using the THz-induced current. Combined with full-wave simulations, we identify THz spectral distortions and reflections arising from THz surface plasmon propagation along the tip wire and cavity modes at the tip apex. By optimizing the tip shape, tip holder geometry and materials, we achieve a drastically flattened THz near-field waveform. This optimization ensures point-like coupling to the far-field and, thus, allows precise Gouy phase control at the STM tip. The improved THz waveforms facilitate atomically-resolved THz time-domain spectroscopy in the STM with high dynamic range for investigating local electron and phonon dynamics on surfaces.

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在扫描隧道显微镜中控制表面等离子体传播和太赫兹近场波形

将亚周期太赫兹脉冲耦合到扫描隧道显微镜（STM）上可实现原子尺度的超快光谱分析。这种技术在很大程度上取决于隧道结中太赫兹近场波形的形状。我们通过对尖端散射的太赫兹光（s-EOS）进行电光采样，并利用太赫兹诱导电流进行脉冲相关，来描述 STM 结中的太赫兹电场波形。结合全波模拟，我们确定了由太赫兹表面等离子体沿尖端导线传播和尖端顶点空腔模式引起的太赫兹光谱畸变和反射。通过优化针尖形状、针尖支架几何形状和材料，我们获得了大幅扁平化的太赫兹近场波形。这种优化确保了与远场的点状耦合，从而在 STM 尖端实现了精确的古伊相位控制。改进后的太赫兹波形有助于在 STM 中进行原子分辨太赫兹时域光谱分析，并具有高动态范围，可用于研究表面上的局部电子和声子动力学。

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来源期刊

Nano Letters 工程技术-材料科学：综合

CiteScore

16.80

自引率

2.80%

发文量

1182

审稿时长

1.4 months

期刊介绍： Nano Letters serves as a dynamic platform for promptly disseminating original results in fundamental, applied, and emerging research across all facets of nanoscience and nanotechnology. A pivotal criterion for inclusion within Nano Letters is the convergence of at least two different areas or disciplines, ensuring a rich interdisciplinary scope. The journal is dedicated to fostering exploration in diverse areas, including: - Experimental and theoretical findings on physical, chemical, and biological phenomena at the nanoscale - Synthesis, characterization, and processing of organic, inorganic, polymer, and hybrid nanomaterials through physical, chemical, and biological methodologies - Modeling and simulation of synthetic, assembly, and interaction processes - Realization of integrated nanostructures and nano-engineered devices exhibiting advanced performance - Applications of nanoscale materials in living and environmental systems Nano Letters is committed to advancing and showcasing groundbreaking research that intersects various domains, fostering innovation and collaboration in the ever-evolving field of nanoscience and nanotechnology.