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arXiv 1005.1332cond-mat.mes-hallcond-mat.mtrl-scicond-mat.str-el
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半导体线之间的色散相互作用

Dispersion interactions between semiconducting wires

Alston J. Misquitta, James Spencer, Anthony J. Stone, Ali Alavi

摘要:

具有非零带隙的扩展分子链(或等效的无限线)之间的色散能通常被假定为可表示为原子-原子项的成对和,其衰减为$R^{-6}$。使用一个模型系统的两个平行的电线与可变带隙,我们表明,这是不是这样的。对于大的线间间距$z$,色散相互作用的尺度为$z^{-5}$,正如绝缘体所预期的那样,但是随着带隙的减小,相互作用大大增强;而在较短(但不重叠)的间距下,它接近于由$z^{-2}$,\emph{i.e.}给出的幂律尺度,\emph{i.e.}是\emph{metallic}线之间预期的色散相互作用。我们证明,这些效果可以理解从等离子体激元模式(电荷波动)的长度尺度的增加,和它们的贡献的分子偶极极化率和色散相互作用,随着带隙的减少。这一结果提出了问题的方法,调用本地化的假设,在推导扩展的小间隙系统之间的色散相互作用。

英文摘要:

The dispersion energy between extended molecular chains (or equivalently infinite wires) with non-zero band gaps is generally assumed to be expressible as a pair-wise sum of atom-atom terms which decay as $R^{-6}$. Using a model system of two parallel wires with a variable band gap, we show that this is not the case. The dispersion interaction scales as $z^{-5}$ for large interwire separations $z$, as expected for an insulator, but as the band gap decreases the interaction is greatly enhanced; while at shorter (but non-overlapping) separations it approaches a power-law scaling given by $z^{-2}$, \emph{i.e.} the dispersion interaction expected between \emph{metallic} wires. We demonstrate that these effects can be understood from the increasing length scale of the plasmon modes (charge fluctuations), and their increasing contribution to the molecular dipole polarizability and the dispersion interaction, as the band gaps are reduced. This result calls into question methods which invoke locality assumptions in deriving dispersion interactions between extended small-gap systems.

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