铜中亚表面Ag和Ge杂质的扫描隧道显微镜研究
Scanning Tunneling Spectroscopy of Subsurface Ag and Ge Impurities in Copper
摘要：
我们使用低温扫描隧道显微镜研究了埋在Cu（100）表面下的单个Ge和Ag杂质。局域态密度中的干涉图样是体杂质的表面散射特征，这是由3D Friedel振荡和电子聚焦效应引起的。比较等电子d散射体Ag和sp散射体Ge允许区分来自杂质散射和宿主的贡献。能量无关的有效散射相移提取使用平面波紧束缚模型，揭示了两个物种相似的值。与从头计算的比较表明，在Ge杂质的非相干sp散射过程。由于这两个散射体是光谱均匀的，扫描隧道光谱的干涉图案产生真实空间签名的散装电子结构。我们发现一个扭结周围的零偏置的两个物种，我们分配到一个重整化的能带结构，由于多体效应，这可以描述与德拜自能和一个令人惊讶的高电子-声子耦合参数$λ$。我们建议，这可能源于在表面附近的批量传播。
英文摘要：
We investigate single Ge and Ag impurities buried below a Cu(100) surface using low temperature scanning tunneling microscopy. The interference patterns in the local density of states are surface scattering signatures of the bulk impurities, which result from 3D Friedel oscillations and the electron focusing effect. Comparing the isoelectronic d scatterer Ag and the sp scatterer Ge allows to distinguish contributions from impurity scattering and the host. Energy-independent effective scattering phase shifts are extracted using a plane wave tight-binding model and reveal similar values for both species. A comparison with ab-initio calculations suggests incoherent sp scattering processes at the Ge impurity. As both scatterers are spectrally homogeneous, scanning tunneling spectroscopy of the interference patterns yields real-space signatures of the bulk electronic structure. We find a kink around zero bias for both species that we assign to a renormalization of the band structure due to many-body effects, which can be described with a Debye self-energy and a surprisingly high electron-phonon coupling parameter $λ$. We propose that this might originate from bulk propagation in the vicinity of the surface.
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