Many-Body Dipole-Dipole Interactions in Atomic Ensembles

多体相互作用在从简单原子到复杂生物分子的各种系统中发挥着重要作用。 偶极-偶极相互作用在蛋白质的形成和折叠中是必不可少的。 这种相互作用可以导致集体和涌现的现象，这些现象不能通过简单地推断几个粒子的微观定律来理解。这项由美国国家科学基金会资助的研究旨在获得对原子系综中多体偶极-偶极相互作用的实验证实的理解。这将通过使用先进的激光光谱技术来实现，该技术对复杂系统中的多体相互作用具有独特的敏感性。将实验结果与模拟结果进行比较，以帮助开发理论模型。这项研究将有助于对相互作用粒子系综中的多体物理学的一般理解，这在从光学原子钟到光合作用等领域具有深远的影响。该项目中开发的实验和理论方法也可用于研究其他多体系统。该项目还包括努力提高佛罗里达国际大学（一所为少数民族服务的机构）在科学和技术方面培训学生的能力，以加强在STEM领域代表性不足的群体的教育。该项目的目标是定量地了解原子系综中的多体偶极-偶极相互作用，其密度在9个数量级之间变化，并且存在或不存在热运动。偶极-偶极相互作用的影响将通过双量子二维相干光谱来探测，该光谱提供了对多体偶极-偶极相互作用的灵敏和无背景检测。飞秒激光脉冲的时间分辨率允许人们在相互作用的瞬态过程中探测动力学。实验将在热的铷原子蒸气和冷的铷原子上进行。热原子蒸气提供了一个广泛的平均原子间的分离和多体动力学与热运动。相比之下，冷原子提供了一个几乎没有热运动的环境。 比较冷原子和热原子的结果使这个小组能够研究热运动对偶极-偶极相互作用的影响。由此产生的结构和动态信息将有助于发展的理论模型的基础上的激子形式主义，占原子系综中的偶极-偶极相互作用。该研究将确定基本参数，如偶极-偶极相互作用强度，有效相互作用范围，相互作用原子的数量，激发诱导的多体状态，缓冲气体的影响，以及偶极-偶极相互作用在原子系综中的热运动的影响。

Many-body interactions play important roles in a variety of systems ranging from simple atoms to complex biological molecules. Dipole-dipole interactions are essential in protein formation and folding. The interactions can lead to collective and emergent phenomena that cannot be understood by a simple extrapolation of the microscopic laws of a few particles. The research supported by this NSF award aims to gain an experimentally confirmed understanding of many-body dipole-dipole interactions in atomic ensembles. This will be accomplished by using an advanced laser spectroscopic technique that is uniquely sensitive to many-body interactions in complex systems. The experimental results will be compared to simulated results to help develop a theoretical model. This research will contribute to the general understanding of many-body physics in an ensemble of interacting particles, which has profound implications in fields ranging from optical atomic clocks to photosynthesis. The experimental and theoretical approaches developed in the project can be used to study other many-body systems as well. This project also includes efforts to enhance the capacity to train students at Florida International University, a minority serving institution, in science and technology, to strengthen the education of underrepresented groups in the STEM fields. The goal of this project is to quantitatively understand many-body dipole-dipole interactions in atomic ensembles, at densities varying across nine orders of magnitude, and both with or without the presence of thermal motion. The effects of dipole-dipole interactions will be probed by double-quantum two-dimensional coherent spectroscopy, which provides a sensitive and background-free detection of many-body dipole-dipole interactions. The temporal resolution of femtosecond laser pulses allows one to probe the dynamics during the transient processes of interactions. The experiments will be performed on a hot atomic rubidium vapor and also with cold rubidium atoms. The hot atomic vapor provides a broad range of mean interatomic separations and many-body dynamics associated with thermal motion. In comparison, the cold atoms provide an environment in the virtual absence of thermal motion. Comparing the results from cold and hot atoms enables this group to study the effects of thermal motion on the dipole-dipole interactions. The resulting structural and dynamic information will contribute to the development of a theoretical model based on the exciton formalism that accounts for the dipole-dipole interactions in an atomic ensemble. The study will determine fundamental parameters such as dipole-dipole interaction strength, effective interaction range, the number of interacting atoms, excitation-induced many-body states, effects of a buffer gas, and effects of thermal motion of the dipole-dipole interaction in atomic ensembles.