台阶硅表面的自旋链和电子转移
Spin Chains and Electron Transfer at Stepped Silicon Surfaces
摘要：
吸附了金的硅的高折射率表面可以重构形成高度有序的线性台阶阵列。这些步骤采取石墨硅的窄条的形式。在某些情况下，特别是对于Si（553）-Au和Si（557）-Au，已知在该带的暴露边缘处的大部分硅原子是自旋极化的并且沿着边缘是电荷有序的。这种电荷排序的周期性总是与沿着台阶边缘的结构周期性相称，因此导致局部磁矩的高度有序阵列，其可以被视为“自旋链”。在这里，我们从理论上和实验上证明，密切相关的Si（775）-Au表面-尽管其非常相似的整体结构-零自旋极化在其台阶边缘。结合使用密度泛函理论和扫描隧道显微镜，我们提出了一个电子计数模型，占这些差异。该模型还预测，无意的缺陷和有意的掺杂剂可以在Si（hhk）-Au台阶边缘产生局部自旋矩。我们详细分析了这些预测之一，并验证了实验。这一发现为使用表面化学和原子操纵技术来创建和控制硅自旋链打开了大门。
英文摘要：
High-index surfaces of silicon with adsorbed gold can reconstruct to form highly ordered linear step arrays. These steps take the form of a narrow strip of graphitic silicon. In some cases - specifically, for Si(553)-Au and Si(557)-Au - a large fraction of the silicon atoms at the exposed edge of this strip are known to be spin-polarized and charge-ordered along the edge. The periodicity of this charge ordering is always commensurate with the structural periodicity along the step edge and hence leads to highly ordered arrays of local magnetic moments that can be regarded as "spin chains". Here, we demonstrate theoretically as well as experimentally that the closely related Si(775)-Au surface has - despite its very similar overall structure - zero spin polarization at its step edge. Using a combination of density-functional theory and scanning tunneling microscopy, we propose an electron-counting model that accounts for these differences. The model also predicts that unintentional defects and intentional dopants can create local spin moments at Si(hhk)-Au step edges. We analyze in detail one of these predictions and verify it experimentally. This finding opens the door to using techniques of surface chemistry and atom manipulation to create and control silicon spin chains.
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