High-Field Terahertz Driven Photocarrier Dynamics in Nanomaterials

非技术摘要本项目的目标是研究半导体材料中的电子在暴露于脉冲短但能量大的电磁波时的运动。更好地了解这种相互作用的基础科学可能会导致制造高速运行的电子和光子设备。自然发生的电磁波充满了日常生活的空间，因此了解半导体中的电子在暴露于高能电磁波时如何反应是很重要的。该研究小组将采用具有大能量的极短电磁脉冲来研究电子在碳纳米管，石墨烯和二氧化钒等纳米尺度材料中的运动。该项目的成果可能会发现新的知识，这些知识对于开发量子信息处理设备和下一代高速电子和光子设备至关重要。该项目还将教育和培训研究生和本科生，使他们获得渊博的知识，为他们在高科技行业就业做好准备。该项目的夏季外展活动包括为波特兰社区学院系统的高中生和少数民族学生提供光学演示和研究经验。技术摘要太赫兹（THz）波段纳米材料中的高场电子动力学是一个未知的课题，考虑到纳米结构在高速电子学和量子信息处理等领域的潜在应用，场控制的重要性再怎么强调也不为过。该项目旨在了解由强太赫兹脉冲驱动的纳米材料中的超快光载流子动力学，其中太赫兹场足够强，可以使材料的电子能带结构发生实质性变化。该研究小组研究了强相关材料二氧化钒中的超快绝缘体-金属转变，由强THz脉冲和飞秒激光激发驱动，并表征了高度非平衡状态下相关电子的动力学。它还研究了低维材料中高场光生载流子动力学的微观机制，如碳纳米管，石墨烯和二硫化钼，在极端条件下，太赫兹场足够强，足以诱导带到带隧穿。时间分辨光学和太赫兹光谱是用来观察和相干控制的极端非平衡动力学的许多电子与亚皮秒分辨率，同时利用场增强和亚波长限制在太赫兹等离子体激元器件。该研究项目为超高速电子和光子学的潜在应用奠定了基础，如场效应晶体管，光调制器，无线互连和频率转换器。从这项研究中获得的基本认识和实验方法是有价值的信息，研究高场光-物质相互作用在各种材料系统，如非谐声子动力学在固体中，超导体的非微扰动力学，和分子中的非线性振动。太赫兹等离子体器件的场增强和亚波长聚焦可以应用于成像和传感应用。从事该研究项目的学生将获得有关使用最先进的光电仪器进行实验的基本科学和技术技能的深刻知识。该项目涉及本科生研究人员从事他们的高级论文或参加REU活动，并支持外展活动，激发年轻人的思想。该奖项反映了NSF的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。

Non-Technical AbstractThe goal of this project is to study the movement of electrons in semiconductor materials when exposed to electromagnetic waves with short pulses but large energy. Better knowledge of the fundamental science of this interaction could lead to making electronic and photonic devices that operate at high-speed. Naturally occurring electromagnetic waves fill up space of everyday life, so it is important to understand how electrons in semiconductors react when exposed to high-energy electromagnetic waves. This research team will employ extremely short electromagnetic pulses with large energy to investigate the movement of electrons in materials with nanometer-scale dimensions such as carbon nanotubes, graphene and vanadium dioxide. The outcome of this project could uncover new knowledge crucial for developing devices for quantum information processing and for the next generation high-speed electronic and photonic devices. This project will also educate and train graduate and undergraduate students, giving them profound knowledge that will prepare them for employment in high-tech industries. The summer outreach activities in the project include optics demonstrations and research experience for high school students and minority students in the Portland Community College system. Technical AbstractHigh-field electron dynamics in nanomaterials in the terahertz (THz) regime is an uncharted subject, yet the importance of field-control of nanostructures cannot be emphasized enough considering its potential application to high-speed electronics and quantum information processing among other areas. This project aims to understand ultrafast photocarrier dynamics in nanomaterials driven by intense terahertz pulses, where the terahertz field is strong enough to make substantial changes in the electronic band structure of the material. The research team investigates ultrafast insulator-to-metal transition in a strongly correlated material, vanadium dioxide, driven by strong THz pulses and femtosecond laser excitations, and characterize the dynamics of correlated electrons in highly non-equilibrium states. It also studies the microscopic mechanisms underlying the high-field photocarrier dynamics in low-dimensional materials, such as carbon nanotubes, graphene and molybdenum disulfide, under extreme conditions where the THz field is strong enough to induce band-to-band tunneling. Time-resolved optical and THz spectroscopy is employed to observe and to coherently control the extreme non-equilibrium dynamics of many electrons with sub-picosecond resolution, while exploiting the field enhancement and subwavelength confinement in THz plasmonic devices. This research project lays the groundwork for the potential applications to ultrahigh-speed electronics and photonics such as field-effect transistors, optical modulators, wireless interconnects, and frequency converters. The fundamental understandings and experimental methods obtained from this research is valuable information for studying high-field light-matter interactions in various material systems such as anharmonic phonon dynamics in solids, nonperturbative dynamics of superconductors, and nonlinear vibrations in molecules. The field enhancement and subwavelength focusing in terahertz plasmonic devices can be applied to imaging and sensing applications. The students working on the research project will gain profound knowledge about the fundamental science and technical skills to conduct experiments using state-of-the-art optoelectronic instruments. The project involves undergraduate researchers working on their senior thesis or participating in REU activities and support outreach activities inspiring young minds.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.