CAREER: Many-electron interactions and excited-state properties in two-dimensional van der waals interfaces

职业：二维范德华界面中的多电子相互作用和激发态特性

• 批准号: 1455346
• 负责人: Li Yang
• 金额: $ 47.5万
• 依托单位: Washington University
• 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: 2015-07-01 至 2020-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1455346&HistoricalAwards=false
• 关键词: CAREER; Many; electron; interactions; excited

NON-TECHNICAL SUMMARYInterfaces in solids, such as p-n junctions and heterojunctions in diodes and transistors, are excellent platforms for fundamental scientific research, and they are the foundation of the microelectronics industry. In these structures, a very large number of electrons interact with each other and shape the conductance, thermal activity, magnetism, optical response, and other fundamental properties of the materials. This CAREER award supports theoretical and computational research and education, in which the PI will focus on many-electron interactions in a new type of structure that can be viewed as "sandwiches" of two-dimensional layers of different materials. The layers are held together by weak forces called van der Waals (vdW) forces. Materials with interfaces in which vdW forces dominate combine the properties of the different layers in exotic ways to produce novel effects, such as unusual light-matter interactions and charge transport. Thus, such materials are useful for studying new physical phenomena and for designing small electronic devices of targeted functionalities. The PI will use parameter-free quantum mechanical simulations and simpler models based on these computations to explore how electronic interactions at vdW interfaces yield unique electrical transport and optical properties. This research can pave the way towards manipulating electronic, thermal, and optical properties of devices, such as diodes, transistors and low-cost photovoltaic solar cells. The educational component of this activity includes student mentoring, course development, seminars and workshops, and diverse collaborations involving students. In particular, the PI will focus on various K-12 activities. Collaborations with neighboring and international institutes will provide opportunities for training under-represented minority students in science, technology, engineering, and mathematics fields.TECHNICAL SUMMARYGraphene and related two-dimensional structures have attracted a great deal of scientific and technological interest over the last decade. Towards this end, few-layer heterostructures and superlattices held together by interlayer van der Waals (vdW) interactions have recently been fabricated. Creating few-layer composites of different materials allows one to achieve a wide range of new material characteristics - the individual materials' properties do not simply superpose. Accordingly, it is very likely that vdW interfaces will be central to the future of scientific and industrial research based on two-dimensional materials. This CAREER award supports theoretical and computational research and education focused on many-electron interactions and excited-state properties of these interfaces.The research plan includes three facets:1. At the single-particle excitation level, the PI and his team will compute the quasiparticle band offsets and charge transfer at vdW junctions, which dictate their electrical and transport properties. The team will further develop practical methods for engineering these characteristic properties. Ultimately, the aim is to design a new type of low-power-dissipation diode that is based on quantum tunneling across vdW junctions.2. At the two-particle excitation level, the project focuses on optical excitations: excitons (electron-hole pairs). The electron-hole binding energy spectra of unique interlayer and intralayer excitons will be computed for vdW heterostructures, which is ultimately expected to lead to a parameter-free exciton model. The team will also focus on physical and chemical approaches for manipulating the energy spectra, optical activities, and lifetimes of these excitons in few-layer and superlattice structures. These ideas will be applied toward achieving exciton Bose-Einstein condensation and designing photovoltaic devices.3. At the higher-order excitations level, the project will focus on three-body interactions (trions) and four-body interactions (biexcitons). By modeling the screened Coulomb interactions in vdW interfaces based on first principles simulations, the PI will develop efficient means for obtaining the energy spectra and optical activities of trions and biexcitons. These models are particularly useful for interpreting experimental results and predicting new optical devices without requiring costly first-principles simulations.The educational component of this activity includes student mentoring, course development, seminars and workshops, and diverse collaborations involving students. In particular, the PI will focus on various K-12 activities. Collaborations with neighboring and international institutes will provide opportunities for training under-represented minority students in science, technology, engineering, and mathematics fields.

固体中的界面，如二极管和晶体管中的pn结和异质结，是基础科学研究的优秀平台，是微电子工业的基础。在这些结构中，大量的电子相互作用，形成材料的电导率、热活性、磁性、光学响应和其他基本性质。这个职业奖支持理论和计算研究和教育，其中PI将专注于一种新型结构中的多电子相互作用，这种结构可以被视为不同材料的二维层的“三明治”。这些层被称为范德华力（vdW）的弱力维系在一起。具有vdW力主导的界面的材料以奇特的方式结合了不同层的特性，产生了新奇的效果，例如不寻常的光-物质相互作用和电荷传输。因此，这些材料对于研究新的物理现象和设计具有目标功能的小型电子设备是有用的。PI将使用无参数量子力学模拟和基于这些计算的更简单模型来探索vdW界面上的电子相互作用如何产生独特的电传输和光学特性。这项研究可以为控制器件的电子、热学和光学特性铺平道路，如二极管、晶体管和低成本光伏太阳能电池。这项活动的教育部分包括学生指导、课程开发、研讨会和讲习班，以及涉及学生的各种合作。特别是，PI将重点关注K-12的各种活动。与邻国和国际机构的合作将为在科学、技术、工程和数学领域培养未被充分代表的少数民族学生提供机会。在过去的十年里，石墨烯和相关的二维结构吸引了大量的科学和技术兴趣。为了达到这个目的，最近已经制造出了由层间范德华相互作用结合在一起的几层异质结构和超晶格。创建不同材料的几层复合材料允许人们获得广泛的新材料特性-单个材料的特性不是简单地叠加。因此，vdW界面很可能成为未来基于二维材料的科学和工业研究的核心。该职业奖支持多电子相互作用和这些界面的激发态特性的理论和计算研究和教育。研究计划包括三个方面：1.研究计划；在单粒子激发水平，PI和他的团队将计算准粒子带偏移和vdW结的电荷转移，这决定了它们的电学和输运性质。该团队将进一步开发实用的方法来设计这些特性。最终，我们的目标是设计一种新型的低功耗二极管，它是基于量子隧道穿越vdW结。在双粒子激发水平，该项目侧重于光激发：激子（电子-空穴对）。计算了vdW异质结构中不同层间和层内激子的电子-空穴结合能谱，最终得到了无参数激子模型。该团队还将专注于物理和化学方法，以操纵能量谱，光学活动，以及这些激子在少层和超晶格结构中的寿命。这些想法将应用于实现激子玻色-爱因斯坦凝聚和设计光伏器件。在高阶激发水平上，该项目将重点关注三体相互作用（trions）和四体相互作用（biexcitons）。通过基于第一性原理模拟的vdW界面中屏蔽的库仑相互作用的建模，PI将开发有效的方法来获得trions和bi激子的能谱和光学活性。这些模型对于解释实验结果和预测新的光学器件特别有用，而不需要昂贵的第一原理模拟。这项活动的教育部分包括学生指导、课程开发、研讨会和讲习班，以及涉及学生的各种合作。特别是，PI将重点关注K-12的各种活动。与邻国和国际机构的合作将为在科学、技术、工程和数学领域培养未被充分代表的少数民族学生提供机会。