Graphene-based all-proximity-coupled quantum spintronic devices

基于石墨烯的全邻近耦合量子自旋电子器件

• 批准号: 1610447
• 负责人: Jing Shi
• 金额: $ 37.5万
• 依托单位: University of California-Riverside
• 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 2019-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1610447&HistoricalAwards=false
• 关键词: Graphene; based; proximity; coupled; quantum

Owing to graphene's unique band structure, two new topological quantum phenomena can emerge: the quantum spin Hall effect (QSHE) and the quantum anomalous Hall effect (QAHE), both offering attractive potential for quantum spintronic applications. A common prerequisite for these two quantum phenomena is strong spin-orbit coupling, either intrinsic or the Rashba type. Of the two phenomena, QAHE requires additional exchange interaction or ferromagnetism in graphene. Although native graphene has neither interaction, its open and flexible structure allows modifications of the properties by proximity coupling to other materials. The proposed quantum phenomena based on quantized anomalous Hall effect can be potentially used for dense, robust, low-power, and scalable non-volatile memory which will drastically improve the performance of the current memory devices based on magnetic tunnel junctions. The non-volatile memory devices are ubiquitous in the modern society. High-performance memory devices based on quantum spintronic phenomena will have a significant impact on low power memory. PI proposes to train the undergraduate and graduate students, especially the underrepresented minority students by engaging them with research projects and teaching them newly developed elective courses. The also PI plans to continue outreach activities to a STEM school by coaching the Science Olympiad events to STEM High school students as well as giving lectures to the summer Physics teachers from southern California high schools during Physics Teacher Summer Academy sponsored by the Physics Department. PI's group has successfully demonstrated the anomalous Hall effect in graphene via the proximity coupling with a magnetic insulator. More recently, PI's group also demonstrated a strong enhancement of spin-orbit coupling via the proximity effect with a transition metal dichalcogenide material (e.g. WS2). In this work, the PI aims to explore the induced effects in all-proximity coupled graphene devices, which acquire new interactions for realizing the predicted quantum effects at relatively high temperatures. Currently few materials are predicted and even fewer materials have been experimentally shown to exhibit QSHE (e.g. HgTe/CdTe quantum wells) and QAHE (e.g. magnetic topological insulators). These materials are extremely difficult to be synthesized or only show the desired properties at extremely low temperatures. The proposed graphene-based devices are ideal systems in which the required interactions can be induced by proximity effects. Those quantum phenomena have not yet been explored in graphene, but it I expected to show many novel and interesting properties, such as quantized transport, robust Hall voltages, pure spin current, etc. These unmatched properties, if demonstrated at high temperatures, can potentially revolutionize the present-day spin electronics. In this proposed research, the PI plans to demonstrate a prototype quantum spintronic memory device based on QAHE. The knowledge learned in the graphene-based devices will deepen our fundamental understanding of two-dimensional electron systems with tunable interactions.

由于石墨烯独特的能带结构，可以出现两种新的拓扑量子现象：量子自旋霍尔效应（QSHE）和量子反常霍尔效应（QAHE），这两种现象都为量子自旋电子学应用提供了诱人的潜力。 这两种量子现象的共同先决条件是强自旋轨道耦合，无论是内在的还是Rashba类型。在这两种现象中，QAHE需要额外的交换相互作用或石墨烯中的铁磁性。虽然天然石墨烯没有相互作用，但其开放和灵活的结构允许通过与其他材料的邻近耦合来修改性质。 基于量子化反常霍尔效应的量子现象可以潜在地用于密集、鲁棒、低功耗和可扩展的非易失性存储器，这将极大地改善当前基于磁性隧道结的存储器件的性能。非易失性存储器件在现代社会中无处不在。基于量子自旋电子学现象的高性能存储器件将对低功耗存储器产生重大影响。PI建议培训本科生和研究生，特别是代表性不足的少数民族学生，让他们参与研究项目，并教授他们新开发的选修课程。PI还计划继续开展STEM学校的外展活动，为STEM高中学生辅导科学奥林匹克活动，并在物理系赞助的物理教师暑期学院期间为来自南加州高中的暑期物理教师讲课。PI的团队已经成功地证明了石墨烯中的异常霍尔效应，通过与磁性绝缘体的邻近耦合。 最近，PI的小组还证明了通过与过渡金属二硫属化物材料（例如WS 2）的邻近效应的自旋轨道耦合的强烈增强。在这项工作中，PI的目的是探索所有邻近耦合石墨烯器件中的诱导效应，这些器件在相对较高的温度下获得新的相互作用以实现预测的量子效应。目前，很少有材料被预测，甚至更少的材料已被实验证明表现出QSHE（例如HgTe/CdTe量子威尔斯）和QAHE（例如磁性拓扑绝缘体）。 这些材料极难合成或仅在极低的温度下显示出所需的性能。所提出的石墨烯基器件是理想的系统，其中所需的相互作用可以通过邻近效应来诱导。这些量子现象尚未在石墨烯中探索，但我期望它显示出许多新颖有趣的特性，如量子化输运，鲁棒的霍尔电压，纯自旋电流等。在这项拟议的研究中，PI计划展示基于QAHE的量子自旋电子存储器原型设备。 在石墨烯基器件中学到的知识将加深我们对具有可调相互作用的二维电子系统的基本理解。