Spectral electronic properties of noble metal nanowires with controlled architectures

具有受控结构的贵金属纳米线的光谱电子特性

• 批准号: 221711328
• 负责人: Privatdozent Dr. Jörg Schäfer
• 金额: --
• 依托单位: Lehrstuhl für Experimentelle Physik IV
• 依托单位国家: 德国
• 项目类别: Research Units
• 财政年份: 2012
• 资助国家: 德国
• 起止时间: 2011-12-31 至 2019-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/221711328?language=en
• 关键词: Spectral; electronic; properties; noble; metal

This project continues the fruitful investigations of the first period focused on the electronic properties of quasi-one-dimensional (quasi-1D) self-assembled atom chains hosted on high-index semiconductor terraces. Key model systems are given by the family of nanowires formed by the noble metal Au on Si (hhk) substrates, e.g., Si(553) and Si(775), which has received and important extension to Ge(hhk)-Au discovered in our group. The central idea is that variation of the crystal index (and hence the terrace width) allows to tune the inter-chain coupling and the phenomena associated with it. These materials thus open the door to witness exciting fundamental physics, such as the role of strong spin-orbit coupling (SOC) which splits the electron bands by their spin character, and ¿ based on the multiple Fermi surface nesting conditions ¿ the possibility of Peierls instabilities with metal-insulator transitions as a function of temperature. In addition, as recent development fostered by our studies in the first funding period, indications have emerged that the step edges of the silicon terraces are spin-polarized, with a long-range antiferromagnetic ordering, as seen in Si(553)-Au. We access these effects by scanning tunneling microscopy (STM) and spectroscopy (STS), which is complemented by angle-resolved photoemission (ARPES), all of which is performed down to low temperatures. Major new avenues for the current funding period are functional modifications to the systems, especially by doping, and, importantly, by change of substrate material (Si vs. Ge). Supported by a first successful demonstration, a change of band-filling induced by doping can indeed give rise to an energy gap in the Au chains ¿ which means that the wires can be switched ¿on¿ and ¿off¿ in a controlled manner. As a novel thrust for this period, replacing the Si(hhk) substrate with Ge(hhk) will imply an altered physical scenario, namely a change of lattice parameter, screening and hybridization. This awaits detailed study of the effects on both the Au chains as well as on the edge magnetism, respectively. For all materials, we will also carefully look at the effects of doping-induced charge transfer on the magnetic pattern. Likewise we want to explore the role of added magnetic impurities. ¿ While many of these phenomena can be accessed by our high-resolution spectroscopy methods, important aspects will be done in collaboration with other projects, including spin-sensitive STM, time-resolved electron diffraction, transport and optical signatures. These joint experiments will be accompanied by predictive modeling in the two theory projects.

该项目延续了第一阶段对高指数半导体平台上准一维(准一维)自组装原子链的电子性质的研究成果。主要的模型体系是由贵金属Au在Si(HHK)衬底上形成的纳米线家族，例如Si(553)和Si(775)，它是我们小组发现的Ge(HHK)-Au的重要扩展。中心思想是，晶体折射率的变化(因此阶地宽度)允许调节链间耦合和与之相关的现象。因此，这些材料打开了见证激动人心的基本物理的大门，例如强自旋轨道耦合(SOC)的作用，它根据电子带的自旋特征分裂电子带，以及基于多重费米表面嵌套条件的Peierls不稳定性的可能性，金属-绝缘体的转变是温度的函数。此外，由于我们在第一个资助期的研究促进了最近的发展，有迹象表明，硅平台的台阶边缘是自旋极化的，具有长程反铁磁有序，如在Si(553)-Au中所见。我们通过扫描隧道显微镜(STM)和光谱学(STS)来了解这些效应，而角度分辨光电子能谱(ARPES)是由角度分辨光电发射(ARPES)补充的，所有这些都是在低温下进行的。本供资期间的主要新途径是对系统进行功能修改，特别是通过掺杂，以及更重要的是通过改变衬底材料(硅与锗)。第一个成功的演示表明，掺杂引起的能带填充变化确实会导致Au链中的能隙，这意味着可以以受控的方式接通和断开导线。作为这一时期的新推力，用Ge(HHK)取代Si(HHK)衬底将意味着改变物理场景，即改变晶格参数、筛选和杂交。这还有待详细研究分别对Au链和边缘磁性的影响。对于所有材料，我们还将仔细观察掺杂诱导的电荷转移对磁性图案的影响。同样，我们想要探索添加磁性杂质的作用。虽然我们的高分辨率光谱学方法可以研究其中的许多现象，但重要的方面将与其他项目合作完成，包括自旋敏感扫描隧道显微镜、时间分辨电子衍射、输运和光学特征。这些联合实验将伴随着两个理论项目中的预测建模。