EAGER: Layer Resolved Capacitance in Graphene Bilayers

EAGER：石墨烯双层中的层分辨电容

• 批准号: 1636607
• 负责人: Andrea Young
• 金额: $ 10.54万
• 依托单位: University of California-Santa Barbara
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-07-01 至 2017-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1636607&HistoricalAwards=false
• 关键词: EAGER; Layer; Resolved; Capacitance; Graphene

Non-Technical AbstractTwo dimensional materials are composed of layers of atoms that are only a few atoms thick. Recent advances in the fabrication of these materials have led to the development of new types of electronic devices. For these extremely thin layers the quantum nature of the system dominates the properties in new and unusual ways. In these materials spontaneous ordering, similar to ferromagnetism, can occur and the topology of the system can affect the properties. However, these materials offer the advantage that electric fields can be used to modify the properties. This leads to new possibilities for enhancing the functionality of quantum electronic devices. This project aims to develop a new, ultrasensitive capacitive technique to study these materials. The novel measurement toolkit, moreover, will aid other scientists in the field studying devices relevant to electronics and energy harvesting. Undergraduate and graduate students will be trained in experimental design, device fabrication, and cryogenic measurement, advancing a new generation of condensed matter physicists ready to take on challenging problems across materials and measurement science.Technical abstract:The project will develop and provide a proof of principle for a capacitive measurement technique that directly senses electronic compressibility, layer polarization, and layer polarizability in atomic bilayers. The technique relies on the small difference in geometric capacitance between a bilayer and two proximal gates caused by interlayer motion of electrons, detected using a multiplexed high current gain cryogenic amplifier. The proposed research will enhance understanding of the physics of graphene bilayers by exhaustively cataloging integer and fractional quantum Hall effects and symmetry protected edge states, using a combination of thermodynamic and charge transport techniques. In Bernal-stacked graphene bilayers, the Principal Investigator will directly resolve valley- and orbital-order in the zero energy Landau level, with additional work to detect thermodynamic anomalies associated with the still poorly understood zero magnetic field correlated phase. Layer polarization and polarizability measurements effected by measuring diverse capacitance observables in a dual gated device will allow unambiguous observation of interlayer coherent states and disambiguation of the charge-valley-orbital symmetry breaking mechanisms. In large twist angle graphene bilayers, bulk and edge probes will be used to search for quantum spin Hall effects of both normal and fractionalized electronic degrees of freedom. In small angle bilayers, the measurements will reveal the basic parameters of physical and electronic structure, specifically the role of elastic strain reconstructions when the layers are nearly aligned. At high magnetic fields bulk and edge measurements will permit disentanglement of intertwined ferromagnetic, fractional, and fractal quantum Hall physics.

二维材料是由只有几个原子厚的原子层组成的。这些材料制造的最新进展导致了新型电子设备的发展。对于这些极薄的层，系统的量子特性以新的和不寻常的方式主导着这些特性。在这些材料中，可以发生类似铁磁性的自发有序，并且系统的拓扑结构可以影响其性质。然而，这些材料的优点是电场可以用来改变其性质。这为增强量子电子器件的功能带来了新的可能性。本项目旨在开发一种新的超灵敏电容技术来研究这些材料。此外，这种新颖的测量工具包将帮助其他科学家研究与电子和能量收集相关的设备。本科生和研究生将接受实验设计、设备制造和低温测量方面的培训，培养新一代凝聚态物理学家，使他们能够在材料和测量科学领域解决具有挑战性的问题。技术摘要：该项目将开发并提供电容测量技术的原理证明，该技术可直接感知原子双层中的电子压缩性、层极化和层极化率。该技术依赖于由电子层间运动引起的双层和两个近端栅极之间的几何电容的微小差异，使用多路复用高电流增益低温放大器检测。该研究将利用热力学和电荷输运技术的结合，对整数和分数量子霍尔效应以及对称保护边缘状态进行详尽的编目，从而增强对石墨烯双层物理的理解。在bernal堆叠的石墨烯双层中，首席研究员将直接解析零能量朗道能级的谷序和轨道序，并进行额外的工作，以检测与仍然知之甚少的零磁场相关相相关的热力学异常。通过测量双门控器件中不同的电容观测值来影响层极化和极化率测量，将允许对层间相干态的明确观察和电荷谷-轨道对称破缺机制的消除。在大扭转角石墨烯双层中，体探针和边缘探针将用于寻找正常和分数化电子自由度的量子自旋霍尔效应。在小角度双层结构中，测量将揭示物理和电子结构的基本参数，特别是当层几乎对齐时弹性应变重建的作用。在高磁场下，体积和边缘测量将允许解开纠缠在一起的铁磁、分数和分形量子霍尔物理。