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扮演着重要的角色。偶极-偶极相互作用在蛋白质的形成和折叠过程中是必不可少的。这种相互作用可能导致集体和紧急现象，而这些现象不是通过简单地推断几个粒子的微观规律就能理解的。这项由NSF奖项支持的研究旨在通过实验证实对原子系综中多体偶极-偶极相互作用的理解。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特别敏感。实验结果将与模拟结果进行比较，以帮助建立理论模型。这项研究将有助于对相互作用粒子系综中的多体物理的总体理解，这在从光学原子钟到光合作用等领域具有深远的意义。该项目所开发的实验和理论方法也可用于其他多体系统的研究。该项目还包括努力提高佛罗里达国际大学的学生在科学和技术方面的培训能力，这是一所为少数族裔服务的机构，以加强对STEM领域中代表不足的群体的教育。这个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，密度在九个数量级上变化，并且两者都有或没有热运动的存在。偶极-偶极相互作用的效应将通过双量子二维相干光谱来探测，它提供了一种灵敏的、无背景的多体偶极-偶极相互作用的检测。飞秒激光脉冲的时间分辨率使人们能够探测相互作用的瞬时过程中的动力学。这些实验将在热原子Rb蒸气上进行，也将在冷Rb原子上进行。热原子蒸气提供了与热运动有关的广泛的平均原子间分离和多体动力学。相比之下，冷原子提供了一个实际上没有热运动的环境。通过比较冷原子和热原子的结果，该小组能够研究热运动对偶极-偶极相互作用的影响。由此得到的结构和动态信息将有助于基于激子形式的理论模型的发展，该理论模型解释了原子系综中的偶极-偶极相互作用。这项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，以及原子系综中偶极-偶极相互作用的热运动效应。

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.