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arXiv 1301.0184cond-mat.mes-hall
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基于第一性原理的金属纳米薄膜中空间分辨量子等离子体激元模

Spatially resolved quantum plasmon modes in metallic nano-films from first principles

Kirsten Andersen, Karsten W. Jacobsen, Kristian S. Thygesen

摘要:

电子能量损失谱(EELS)可用于探测纳米结构材料中的等离子体激元激发,具有原子尺度的空间分辨率。对于小于几个纳米的结构,量子效应预计是重要的,限制了广泛使用的半经典响应模型的有效性。在这里,我们提出了一种方法来识别和计算空间分辨等离子体模式的第一原则的基础上的动态介电函数的频谱分析。作为一个例子,我们计算的等离子体振子模式的0.5-4 nm厚的钠膜,并发现它们可以被分类为(传统的)表面模式,次表面模式,和一组离散的体模式类似于整个薄膜的驻波。我们发现了量子限制和非局域响应的明显效果。量子等离子体激元模式提供了一个直观的图片集体激发的限制电子系统,并提供了一个清晰的解释空间分辨EELS光谱。

英文摘要:

Electron energy loss spectroscopy (EELS) can be used to probe plasmon excitations in nanostructured materials with atomic-scale spatial resolution. For structures smaller than a few nanometers quantum effects are expected to be important, limiting the validity of widely used semi-classical response models. Here we present a method to identify and compute spatially resolved plasmon modes from first principles based on a spectral analysis of the dynamical dielectric function. As an example we calculate the plasmon modes of 0.5-4 nm thick Na films and find that they can be classified as (conventional) surface modes, sub-surface modes, and a discrete set of bulk modes resembling standing waves across the film. We find clear effects of both quantum confinement and non-local response. The quantum plasmon modes provide an intuitive picture of collective excitations of confined electron systems and offer a clear interpretation of spatially resolved EELS spectra.

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