CAREER: Modifying Electron-Electron Interactions to Control the Optical and Electronic Properties of Carbon Nanotubes

*技术摘要*载流子之间的强库仑相互作用是低维电子系统(如碳纳米管)的一个重要特征。与强相互作用相关的现象往往挑战理论描述，并可能导致技术上的新突破。在这个项目中，碳纳米管中的电子-电子(e-e)相互作用将通过操纵碳纳米管周围的介电环境来改变。通过研究电子-电子相互作用“开启”然后“关闭”的单个碳纳米管器件，拟议的实验将测试关于带隙重整化、光吸收截面、光电流产生效率、碰撞电离率和Luttinger液体行为的理论。据预测，修改e-e相互作用将导致所有这些性质的巨大变化。实验的成功完成将确定电子相互作用如何改变纳米材料的性质，从而产生关于如何设计具有特定性质的纳米材料的基础知识。这些实验还将直接有助于太阳能电池设计的发展，打破太阳能转换效率的传统限制。该项目支持博士生和本科生，他们将接受纳米制造和纳米计量学技术的强大组合培训。在该项目期间开发的纳米科学活动将接触到广泛的受众，包括农村高中课堂和物理入门课程。*非技术抽象*计算机芯片和光伏电池等设备是基于我们对材料内部电子的理解和控制。在大多数材料中，电子相互独立地运动，这简化了理论，但限制了发现新现象的可能性。然而，在碳纳米管等材料中，由于材料的纳米级几何形状，电子之间的排斥作用非常强。如果一个电子在碳纳米管内跳舞，其他电子也会跳舞。与这种集体电子舞蹈相关的新现象包括更快的信号传播速度和更高的太阳能转换效率。要理解和利用与纳米材料中电子之间的强相互作用有关的现象，还需要做很多工作。在这个项目中，将在各种条件下对单个碳纳米管进行测量，这些条件旨在促进或抑制集体电子舞蹈。实验的成功完成将确定电子相互作用如何改变纳米材料的性质，从而产生关于如何设计具有特定性质的纳米材料的基础知识。这些实验还将直接有助于太阳能电池设计的发展，打破太阳能转换效率的传统限制。该项目支持博士生和本科生，他们将接受纳米制造和纳米计量学技术的强大组合培训。在该项目期间开展的纳米科学活动将惠及广大受众，包括农村高中课堂和物理入门课程。

***TECHNICAL ABSTRACT***Strong Coulomb interactions between charge carriers are a defining feature in low-dimensional electronic systems such as carbon nanotubes (CNTs). Phenomena associated with strong interactions often challenge theoretical descriptions and can lead to new breakthroughs in technology. In this project, electron-electron (e-e) interactions in CNTs will be varied by manipulating the dielectric environment surrounding the CNT. By studying individual CNT devices with e-e interactions "turned on" and then "turned off", the proposed experiments will test theories about bandgap renormalization, photoabsorption cross-section, photocurrent generation efficiency, impact ionization rates, and Luttinger liquid behavior. It is predicted that modifying the e-e interactions will causes dramatic changes in all these properties. Successful completion of the experiments will establish how electron interactions modify the properties of a nanomaterial, thereby generating fundamental knowledge about how to engineer nanomaterials with specific properties. The experiments will also directly contribute to the development of a solar cell design that breaks the conventional limit for solar energy conversion efficiency. The project supports PhD students and undergraduates who will be trained in a powerful combination of nanofabrication and nanometrology techniques. Nanoscience activities developed during the project will reach a broad audience, including rural highschool classrooms and introductory physics classes.***NONTECHNICAL ABSTRACT***Devices such as computer chips and photovoltaic cells are based on our understanding and control of electrons inside of materials. In most materials, electrons move independently of one another, which simplifies theory but limits the possibilities of discovering new phenomena. In materials such as carbon nanotubes, however, the repulsive interactions between electrons are extremely strong due to the nanoscale geometry of the material. If one electron dances about inside a carbon nanotube, the other electrons dance too. New phenomena related to this collective electron dance include faster signal propagation speeds and higher efficiency solar energy conversion. Much work is required to understand and utilize the phenomena related to the strong interactions between electrons in nanomaterials. In this project, measurements of individual carbon nanotubes will be made in a variety of conditions that are designed to promote or suppress the collective electron dance. Successful completion of the experiments will establish how electron interactions modify the properties of a nanomaterial, thereby generating fundamental knowledge about how to engineer nanomaterials with specific properties. The experiments will also directly contribute to the development of a solar cell design that breaks the conventional limit for solar energy conversion efficiency. The project supports PhD students and undergraduates who will be trained in a powerful combination of nanofabrication and nanometrology techniques. Nanoscience activities developed during the project will reach a broad audience, including rural high school classrooms and introductory physics classes.