CAREER: Correlated Topological States in van der Waals Bilayers

非技术摘要二维材料是由只有一个或两个原子厚度的原子层组成的，排列在一个完美的晶格中。在这些材料的制造方面的最新进展导致了新型电子设备的发展，这有助于推动电子部件的缩放或引入基于全新功能的电子设备。至关重要的是，在极薄的层中，系统的量子性质以新的和不同寻常的方式主导着电子性质。例如，自发有序，类似于铁磁性，可以在层之间发生。电场可以用来改变材料的性质，为增强量子电子器件的功能提供了新的可能性。该项目开发了一种新的、超灵敏的电容技术来研究这些材料，以及基于二维材料的电子设备的新架构。该测量工具包将帮助该领域的其他科学家研究与电子学和能量收集相关的设备，同时在创造更完美的二维设备方面的不断进步揭示了低维电子物质的新物理。本科生和研究生接受了实验设计、器件制造和低温测量方面的培训，促进了新一代凝聚态物理学家的发展，他们准备好接受跨材料和测量科学的挑战性问题。技术摘要这个职业项目开发了一种电容测量技术，可以直接检测原子双层中的电子可压缩性、层极化和层极化，特别是在新一代全范德华器件几何结构中，其中栅电介质和金属材料(除了沟道材料)也由完美的二维晶体制成。该测量技术依赖于双层和两个近端栅极之间的微小几何电容差异，这是由电子的层间运动引起的，使用多路高电流增益低温放大器进行检测。该活动详尽地列出了石墨烯异质结构中的整数和分数量子霍尔效应以及对称性保护的边态，使用了热力学和电荷输运技术的组合，分别探测了体和边。直接的目标包括超清洁的伯纳尔和扭曲的双层石墨烯，该技术允许消除自旋、层和山谷对称性破坏的歧义。器件采用全范德华封装的新技术制造，实现了创纪录的高迁移率，可与所有其他电子系统相媲美或超过。此外，对半导体双层中电荷转移的精确测量还允许对与能量收集相关的光诱导过程进行定量基准测试。除了提供二维材料应用中使用的材料参数的直接、定量基准之外，该活动还通过本科生和研究生研究人员教育的无缝整合以及基于数字和模拟电子的高中水平课堂模块的开发，产生了更广泛的影响。

Non-Technical AbstractTwo dimensional materials are composed of layers of atoms only one or two atoms thick, arranged in a perfect lattice. Recent advances in the fabrication of these materials have led to the development of new types of electronic devices, which can help push the boundaries of scaling electronic components or introduce electronic devices based on completely new functionality. Crucially, in extremely thin layers the quantum nature of the system dominates the electronic properties in new and unusual ways. For example, spontaneous ordering, similar to ferromagnetism, can occur between layers. Electric fields can be used to modify material properties, providing new possibilities for enhancing the functionality of quantum electronic devices. This project develops a new, ultrasensitive capacitive technique to study these materials, along with new architectures for electronic devices based on two dimensional materials. The measurement toolkit will aid other scientists in the field studying devices relevant to electronics and energy harvesting, while continued advances in creating ever more perfect two dimensional devices reveal new physics of low dimensional electronic matter. Undergraduate and graduate students are 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 abstractThis CAREER project develops a capacitive measurement technique that directly senses electronic compressibility, layer polarization, and layer polarizability in atomic bilayers, particularly within a new generation of all-van der Waals device geometries in which gate dielectric and metal materials (in addition to the channel materials) are also made of perfect two dimensional crystals. The measurement 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 activity exhaustively catalogues integer and fractional quantum Hall effects and symmetry protected edge states in graphene heterostructures using a combination of thermodynamic and charge transport techniques which probe the bulk and edge separately. Immediate targets include ultra-clean Bernal and twisted bilayer graphene, where the technique permits the disambiguation of spin, layer, and valley symmetry breaking. Devices are fabricated using a new technique of all-van der Waals encapsulation, allowing record high mobilities rivalling or surpassing what can be achieved in all other electronic systems. Precise measurements of charge transfer in semiconductor bilayers, moreover, allows quantitative benchmarking of photo-induced processes, as are relevant for energy harvesting. In addition to providing direct, quantitative benchmarking of material parameters of use in applications of two dimensional materials, the activity has a broader impact through the seamless integration of undergraduate and graduate researcher education, and the developments of high school level classroom modules based on digital and analog electronics.