School of Engineering Science, College of Engineering, University of Tehran, 16th Azar Street, Enghelab Square, Tehran, Iran.
Institute for Quantum Science and Technology, University of Calgary, Calgary, Alberta T2N 1N4, Canada.
J Chem Phys. 2018 Apr 21;148(15):154701. doi: 10.1063/1.5020873.
Recent work has suggested that coupled silicon dangling bonds sharing an excess electron may serve as building blocks for quantum-cellular-automata cells and quantum computing schemes when constructed on hydrogen-terminated silicon surfaces. In this work, we employ ab initio density-functional theory to examine the details associated with the coupling between two dangling bonds sharing one excess electron and arranged in various configurations on models of phosphorous-doped hydrogen-terminated silicon (100) surfaces. Our results show that the coupling strength depends strongly on the relative orientation of the dangling bonds on the surface and on the separation between them. The orientation of dangling bonds is determined by the anisotropy of the silicon (100) surface, so this feature of the surface is a significant contributing factor to variations in the strength of coupling between dangling bonds. The results demonstrate that simple models for approximating tunneling, such as the Wentzel-Kramer-Brillouin method, which do not incorporate the details of surface structure, are incapable of providing reasonable estimates of tunneling rates between dangling bonds. The results provide guidance to efforts related to the development of dangling-bond based computing elements.
最近的研究表明，当在氢终止的硅表面上构建时，共享一个多余电子的耦合硅悬键可能作为量子细胞自动机单元和量子计算方案的构建模块。在这项工作中，我们采用从头算密度泛函理论研究了在磷掺杂氢终止硅（100）表面模型上以各种构型排列的两个共享一个多余电子的悬键之间耦合相关的细节。我们的结果表明，耦合强度强烈依赖于表面上悬键的相对取向和它们之间的分离。悬键的取向由硅（100）表面的各向异性决定，因此表面的这一特征是导致悬键之间耦合强度变化的重要因素。研究结果表明，不包含表面结构细节的简单隧道模型，如 WKB 方法，无法对悬键之间的隧道速率提供合理的估计。这些结果为基于悬键的计算元件的发展提供了指导。
