Tunable twistronics: local tuning and probing of topological edge states and superconductivity in bilayer graphene

可调谐扭转电子学：双层石墨烯拓扑边缘态和超导性的局部调谐和探测

• 批准号: 437214324
• 负责人: Professor Dr. Christoph Stampfer
• 金额: --
• 依托单位: Laboratoire de Physique de Solides - UMR 8502
• 依托单位国家: 德国
• 项目类别: Research Grants
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/437214324?language=en
• 关键词: Tunable; twistronics; local; tuning; probing

Studying the interface between different correlated electronic systems represents one of the most fundamental and technological challenge for future applications in quantum technologies. In this respect, twisted bilayer graphene (tBLG) which can show superconductivity and topological edge states (among other electronic phases), at some precise twist angles between its layers, seems to be the ideal candidate. However, to achieve these very complex structures it is necessary first to understand their physical origin and how we can control them.In this regard, the general objective of TATTOOS is to provide an experimental and theoretical understanding of the physical origin of both the superconducting state and the existence of topologically protected channels, with the prospect of building clean junctions involving different correlated electronic systems.We propose to investigate first the dependence of these states on the twist angle between the layers, and how their transport properties, down to the nanometer scale, are modified by the twist angle. We plan to do so by using different scanning probe microscopy techniques. The first one allows an in situ mechanical modification of the twist angle between the graphene layers in an electrically-contacted device by applying a lateral force to the uppermost layer. The second one, scanning gate microscopy, will be used to map the electron transport down to ultralow temperature. Combining experimental data with numerical simulations of transport in realistic tBLG model devices, we aim to address fundamental questions such as the physical origin and nature of the superconducting and topologically-protected channel, their spatial homogeneity and robustness against local variations of electrostatic or magnetic environment, among others.Second, we propose to build “all-tBLG” junctions between a superconductor and different other phases, including topologically-protected 1D edge channels. This will be realized through van der Waals stacking of two graphene layers grown by chemical vapor deposition (CVD). While one layer should have a single grain boundary, which is achieved by the merging of two crystals, the other layer should be single crystalline. By the appropriate selection of the alignment of both graphene crystals along the grain boundary, a twist angle of the upper layer should be achieved, which makes it possible, for example, to obtain a superconducting state on one side and topologically protected channels on the other side of the grain boundary.

研究不同相关电子系统之间的界面是未来量子技术应用中最基本和最具技术挑战性的问题之一。在这方面，扭曲双层石墨烯(TBLG)似乎是理想的候选者，它可以在层与层之间精确的扭曲角度下显示超导和拓扑边缘状态(在其他电子相中)。然而，要实现这些非常复杂的结构，首先必须了解它们的物理起源以及我们如何控制它们。在这方面，纹身的总体目标是提供对超导状态和拓扑保护通道的存在的物理起源的实验和理论理解，并有望建立涉及不同相关电子系统的干净的结。我们建议首先研究这些态与层之间的扭角的相关性，以及它们的传输性质如何被扭角改变到纳米级。我们计划通过使用不同的扫描探针显微镜技术来做到这一点。第一种方法通过对最上层施加侧向力，对电接触装置中的石墨烯层之间的扭转角进行原位机械修改。第二种，扫描门显微镜，将被用来描绘电子在超低温下的传输。将实验数据与实际tBLG模型器件中输运的数值模拟相结合，我们旨在解决一些基本问题，如超导和拓扑保护通道的物理起源和性质，它们的空间均匀性和对静电或磁场环境局部变化的稳健性等。第二，我们提出在超导和其他不同相之间建立“全tBLG”结，包括拓扑保护的一维边缘通道。这将通过化学气相沉积(CVD)生长的两层石墨烯的范德瓦尔斯堆积来实现。其中一层应该具有单晶界，这是通过两个晶体的合并实现的，而另一层应该是单晶层。通过适当地选择两个石墨烯晶体沿晶界的取向，可以获得上层的扭转角度，从而可以在晶界一侧获得超导态，在晶界另一侧获得拓扑保护的沟道。