Atomic point contacts down to a single atom have been studied using gold as a model system. Having only a single valence electron, the conductance through one gold atom is predicted to be one quantum unit of conductance (the quantum unit of conductance being 1 Go= 2e2/h =7.748091 x 10-5 S inversely, Ro=1/G o=2e2/h=12,906 O, with e electron charge and h Plank's constant). In the past conductance histograms and other methods have been used as proof or the signature of conductance quantization.;In the present study a mechanical perturbation approach has been developed as a new method to study conductance quantization in atomic point contacts. The peak height and location in the conductance histogram is shown to vary under different degrees of perturbation (extension or compression of the point contact in the range of 100-500 pm), which clearly dispels the idea of conductance histograms as proof of conductance quantization. The first peak in the conductance histogram is generally believed to be the consequence of single-atom contacts and atomic chains, but here it is shown that a significant portion of the first peak can be attributed to a two-atom configuration. Conductance histograms by themselves only show preferred atomic configurations and cannot even provide information on the stability of those configurations. As a result of these findings, previously used noise analysis methods also do not hold as sufficient proof of quantization of conductance. Noise and strain susceptibility measurements of atomic point contacts show that the atomic structure is the most significant factor in the observed behavior. Measurement of the conductance response to a mechanical perturbation shows that the transmission through a single atom contact saturates at 1 Go. This constitutes the first direct proof that the maximum conductance through one gold atom is 1 Go and that conductance quantization is present in gold atoms.
展开▼
机译：已经使用金作为模型系统研究了直至单个原子的原子点接触。仅具有一个价电子，通过一个金原子的电导被预测为一个电导的量子单位（电导的量子单位为1 Go = 2e2 / h = 7.748091 x 10-5 S，反之，Ro = 1 / G o = 2e2 / h = 12,906 O，带电子电荷和h普朗克常数）。在过去，电导直方图和其他方法已被用作电导量化的证明或签名。在本研究中，机械微扰方法已被开发为研究原子点接触中电导量化的一种新方法。电导直方图中的峰高和位置显示在不同程度的扰动下变化（点接触的扩展或压缩在100-500 pm的范围内），这清楚地消除了电导直方图作为电导量化证据的想法。通常认为电导直方图中的第一个峰是单原子接触和原子链的结果，但此处表明，第一峰的很大一部分可以归因于双原子构型。电导直方图本身仅显示首选的原子构型，甚至不能提供有关这些构型稳定性的信息。这些发现的结果是，先前使用的噪声分析方法也没有足够的电导量化证据。原子点接触的噪声和应变敏感性测量表明，原子结构是观察到的行为中最重要的因素。测量对机械扰动的电导响应表明，通过单个原子接触的传输在1 Go时达到饱和。这构成了第一个直接证明，即通过一个金原子的最大电导为1 Go，并且金原子中存在电导量化。
展开▼
