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arXiv 0907.0392cond-mat.mes-hall
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镁合金点触点的金属性能

Metallic properties of magnesium point contacts

R. H. M. Smit, A. I. Mares, M. Haefner, P. Pou, J. C. Cuevas, J. M. van Ruitenbeek

摘要:

我们提出了一个实验和理论研究的Mg原子大小的接触的电导和稳定性。利用机械可控断裂结(MCBJ),我们观察到室温电导直方图呈现出一系列峰,这表明存在壳效应。然而,它的周期性不能简单地用原子或电子壳效应来解释。我们还发现,在室温下,不存在单个原子直径的接触。一个可能的解释可能是发生的金属到绝缘体的过渡,接触半径减小,在类比中,它是已知的镁簇。然而,我们的第一原理计算表明,虽然无限线性链可以是绝缘的,但具有较大原子配位的Mg线,如在现实的原子接触中,总是金属的。最后,在液氦温度下,我们的测量结果表明,电导直方图是由一个明显的峰值在量子电导。这与我们基于紧束缚模型的计算结果非常一致,该模型表明Mg单原子接触的电导主要由单个完全开放的传导通道决定。

英文摘要:

We present an experimental and theoretical study of the conductance and stability of Mg atomic-sized contacts. Using Mechanically Controllable Break Junctions (MCBJ), we have observed that the room temperature conductance histograms exhibit a series of peaks, which suggests the existence of a shell effect. Its periodicity, however, cannot be simply explained in terms of either an atomic or electronic shell effect. We have also found that at room temperature, contacts of the diameter of a single atom are absent. A possible interpretation could be the occurrence of a metal-to-insulator transition as the contact radius is reduced, in analogy with what it is known in the context of Mg clusters. However, our first principle calculations show that while an infinite linear chain can be insulating, Mg wires with larger atomic coordinations, as in realistic atomic contacts, are alwaysmetallic. Finally, at liquid helium temperature our measurements show that the conductance histogram is dominated by a pronounced peak at the quantum of conductance. This is in good agreement with our calculations based on a tight-binding model that indicate that the conductance of a Mg one-atom contact is dominated by a single fully open conduction channel.

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