Transport and Carrier Dynamics Near the Metal-Insulator Transition in VO2

VO2 金属-绝缘体转变附近的输运和载流子动力学

• 批准号: 1508680
• 负责人: Sanjoy Sarker
• 金额: $ 50.36万
• 依托单位: University of Alabama Tuscaloosa
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-09-01 至 2020-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1508680&HistoricalAwards=false
• 关键词: Transport; Carrier; Dynamics; Near; Metal

Non-technical Description: Vanadium dioxide is a material that undergoes a transition from an electrical insulator to an electrical conductor just above room temperature (about 68 degree C). This behavior allows it to act as an electrical switch, which is an essential functionality required for transistors in computers. However, a complete microscopic understanding of this transition is still lacking, hindering future applications of this material. This project combines theoretical and experimental expertise of the team to develop an in-depth understanding of the microscopic mechanisms for the transition and discover new approaches to control it. Experimental characterization acts as a feedback for the further development of theoretical models, and these models also make further theory predictions to guide experimental efforts. Various outreach and education activities include: (1) providing the theoretical and experimental hands-on research experience in highly topical research areas for students; (2) participating in an international internship program to bring in undergraduates during the academic year; (3) disseminating research findings to industry through long-standing industrial collaborations; and (4) broadening the participation of under-represented groups specifically through an existing collaboration with Historically Black Colleges and Universities. Technical Description: Vanadium dioxide transforms from a low-temperature insulating phase to a high-temperature metallic phase, during which the electrical resistivity can change by a factor of as much as 100,000, accompanied by a large change in infrared reflectivity. The fundamental mechanism of the temperature-driven metal-insulator transition of bulk vanadium dioxide (VO2) at 341 K is still under debate, over fifty years after its discovery. Specifically, there is a need to understand the microscopic physics responsible for the anomalous transport properties, in particular the presence of metallic clusters in the insulating state. The mixed phase cannot be explained in terms of a simple phase separation model; nor can a simple semiconductor or percolation model explain the transport. This project combines experimental and theoretical efforts, with each providing a crucial feedback for the other. The approach addresses the relevant physical processes involved, namely electron motion correlated with ionic displacements, at a microscopic level. Detailed experimental transport studies of the mixed phase are a key part of the project, particularly electrical noise and tunneling spectroscopy. The team is also investigating novel transistor-like structures and piezoelectric-induced strain effects with a goal of an electrically controlled transition. The theoretical model contains the essential physics of VO2, by treating it as a strongly interacting electron-ion system. Non-perturbative many-body techniques are applied to study how the transition can occur and metallic clusters appear, beyond the reach of density functional theory,

非技术描述：二氧化钒是一种在室温（约68摄氏度）以上从电绝缘体转变为电导体的材料。这种行为允许它充当电子开关，这是计算机中晶体管所需的基本功能。然而，对这种转变的完整微观理解仍然缺乏，阻碍了这种材料的未来应用。该项目结合了团队的理论和实验专业知识，深入了解转变的微观机制，并发现控制转变的新方法。实验表征作为进一步发展理论模型的反馈，这些模型也进一步做出理论预测，以指导实验工作。各种外展和教育活动包括：（1）为学生提供高度热门研究领域的理论和实验实践研究经验;（2）在学年期间参加国际实习计划，以吸引本科生;（3）通过长期的工业合作向工业界传播研究成果;（4）在国际范围内开展研究活动。以及（4）扩大代表性不足群体的参与，特别是通过与历史上的黑人学院和大学的现有合作。技术说明：二氧化钒从低温绝缘相转变为高温金属相，在此期间，电阻率可以改变多达100，000倍，并伴随着红外反射率的大变化。在发现50多年后，在341 K温度下大块二氧化钒（VO 2）的温度驱动金属-绝缘体转变的基本机制仍然存在争议。具体而言，有必要了解负责的异常传输特性的微观物理，特别是在绝缘状态下的金属簇的存在。混合相不能用简单的相分离模型来解释，也不能用简单的半导体或渗流模型来解释输运。该项目结合了实验和理论工作，每一个都为另一个提供了重要的反馈。该方法在微观水平上解决了相关的物理过程，即与离子位移相关的电子运动。详细的混合相的实验传输研究是该项目的关键部分，特别是电噪声和隧道光谱。该团队还在研究新型晶体管结构和压电诱导应变效应，目标是实现电控过渡。理论模型包含VO 2的基本物理，将其视为强相互作用的电子-离子系统。非微扰多体技术被应用于研究跃迁如何发生和金属团簇的出现，超出了密度泛函理论的范围，