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arXiv 1603.03486cond-mat.str-el
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2 H- NbS2等离激元色散的电子能量损失和含时密度泛函理论研究

Electron-energy-loss and time-dependent density functional theory study on the plasmon dispersion in 2H-NbS2

Pierluigi Cudazzo, Eric Müller, Carsten Habenicht, Matteo Gatti, Helmuth Berger, Martin Knupfer, Angel Rubio, Simo Huotari

摘要:

我们检查了2 $H$ -Cu $_{0.2}$ NbS $_2$中的实验和理论电子能量损失谱,发现该材料中的1 eV等离子体激元没有表现出正常宽抛物带系统所期望的规则正二次等离子体激元色散。相反,我们发现一个几乎非分散的等离子体在动量转移范围$q<0.35$ $^{-1}$。我们认为,对于化学计量纯2 $H$ -NbS $_2$的色散关系预计将有一个负斜率的情况下,其他过渡金属dichalcogenides。稳定晶体生长所需的Cu杂质的存在倾向于将负等离子体激元分散转变为正等离子体激元分散,但是当前系统中的掺杂水平足够小以导致几乎非分散的等离子体激元。我们的结论是,负斜率的等离子体激元色散是不连接的存在的电荷密度波顺序在过渡金属二硫族化合物。

英文摘要:

We examine the experimental and theoretical electron-energy loss spectra in 2$H$-Cu$_{0.2}$NbS$_2$ and find that the 1 eV plasmon in this material does not exhibit the regular positive quadratic plasmon dispersion that would be expected for a normal broad-parabolic-band system. Instead we find a nearly non-dispersing plasmon in the momentum-transfer range $q<0.35$ Å$^{-1}$. We argue that for a stoichiometric pure 2$H$-NbS$_2$ the dispersion relation is expected to have a negative slope as is the case for other transition-metal dichalcogenides. The presence of Cu impurities, required to stabilize the crystal growth, tends to shift the negative plasmon dispersion into a positive one, but the doping level in the current system is small enough to result in a nearly-non-dispersing plasmon. We conclude that a negative-slope plasmon dispersion is not connected with the existence of a charge-density-wave order in transition metal dichalcogenides.

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