Microwave spectroscopy of Josephson-Junctions defined from single layer, bilayer, and trilayer graphene [MEGA-JJ]

由单层、双层和三层石墨烯定义的约瑟夫森结的微波光谱 [MEGA-JJ]

• 批准号: 460755959
• 负责人: Professor Dr. Robert H. Blick
• 金额: --
• 依托单位: Institut für Nanostruktur- und Festkörperphysik (INF)
• 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/460755959?language=en
• 关键词: Microwave; spectroscopy; Josephson; Junctions; defined

During the last couple of years single layer graphene (SLG) matured to a well characterized Dirac-material, which was set for being the poster child of the next generation solid-state textbooks. However, the very recent discovery of superconductivity in bilayer graphene (BLG), sandwiched under a so-called magic angle, underlines that this particular 2D system still has the power to surprise. The fundamental question we intend to address in this proposal is the application of superconducting SLG and ‘magic-moiré’ BLG as microwave devices. Naturally, there are several possible approaches in order to do this. The path we chose to accomplish this is via microwave spectroscopy of SLG and BLG forming Josephson junctions (JJs). As is well known JJs are essential components of microwave circuits in the quantum realm. Since SLG is not superconducting we will be able to conduct proximity tests with superconducting leads formed by conventional metallic superconductors. This will set the stage for probing the potential application of SLG-JJs for microwave detection, heterodyne mixing, and quantum computing circuits. The fundamentally new features of such SLG-JJs are the Dirac-nature of charge carriers in graphene, i.e., constant charge carrier velocity and hence broadband frequency detection ability, the singularity in the density of states at the charge neutrality point, the high carrier velocity, and the tunable carrier concentration of the graphene layers. All this promises unprecedented single-photon detection in the quantum limit. In extension to this we will also make use of superconductivity in BLG in the microwave regime. From this we expect to obtain Shapiro-signatures in the IV-characteristics, which are an essential tool for deriving the very nature of superconductivity in twisted BLG (labeled in the following as TBG) and testing its application for quantum circuits. Consequently, we will be able to investigate the intricate interplay of superconductivity in TBG moiré lattices via microwave spectroscopy. Inserting a JJ in the TBG will then form a fundamentally new microwave detector with potential for up-scaling without the need of superconducting leads.

在过去的几年里，单层石墨烯（SLG）成熟为一种具有良好特征的Dirac材料，它被设定为下一代固态教科书的典范。然而，最近在双层石墨烯（BLG）中发现的超导性，夹在所谓的魔角下，强调了这种特殊的2D系统仍然具有令人惊讶的力量。我们打算解决的基本问题，在这个建议是超导SLG和“魔云纹”BLG作为微波器件的应用。当然，有几种可能的方法可以做到这一点。我们选择的实现这一目标的途径是通过SLG和BLG形成约瑟夫森结（JJ）的微波光谱。众所周知，JJ是量子领域中微波电路的重要组成部分。由于SLG不是超导的，我们将能够用传统金属超导体形成的超导引线进行近距离测试。这将为探索SLG-JJ在微波探测、外差混频和量子计算电路中的潜在应用奠定基础。这种SLG-JJ的基本新特征是石墨烯中电荷载流子的Dirac性质，即，恒定的电荷载流子速度以及因此的宽带频率检测能力、电荷中性点处的态密度的奇异性、高载流子速度以及石墨烯层的可调载流子浓度。所有这些都预示着在量子极限下前所未有的单光子探测。在扩展到这一点，我们也将利用超导电性的大规模在微波制度。由此，我们期望在IV特性中获得Shapiro签名，这是导出扭曲BLG（以下标记为TBG）中超导性的本质并测试其在量子电路中的应用的重要工具。 因此，我们将能够通过微波光谱研究TBG莫尔晶格中超导性的复杂相互作用。在TBG中插入JJ将形成一个全新的微波探测器，具有升级的潜力，而不需要超导导线。