RUI: Topological Excitations in Spinor Bose-Einstein Condensates

长期以来，人类一直对对称性着迷，这是一个任何看过镜子或凝视过自己的左右手的人都熟悉的概念。事实上，对称性是一个基本的组织原则，它出现在每一个科学学科中。在物理学中，对称性通常以拓扑学的形式表现出来，或者研究形状和结构如何相互连续变形。正如2016年诺贝尔奖所承认的那样，拓扑学最近已经成为现代物理学中一个重要且越来越相关的话题。不同物理系统中共享的拓扑特征允许进行互补研究，即使这些系统非常不同。例如，在能量最高的巨型粒子加速器和温度最低的桌面设备中，都可以研究类似的物理学。这项研究的核心超冷环境是一种稀薄气体，冷却到绝对零度以上数百亿分之一度，在这一点上，它会产生一些性质，使其成为一种控制良好的“宇宙”，其中可能会召唤出粒子的类似物，而这些粒子可能--或者更有趣的是，可能不会--出现在“真正的”宇宙中。这个项目将研究这些类粒子现象的产生和时间演化，包括点状单极子和扩展粒子，这些粒子被称为“天空粒子”和“结”。这样的实验可以洞察许多不同拓扑系统的现象和行为，并有助于基于它们的操纵和控制的新兴技术。该科学计划还将通过为几名积极进取的本科生以及一名研究生研究员提供技术和科学培训机会，加强尖端实验研究与本科教育之间的关系。在这些方面，它有助于培养下一代公民科学家。类粒子拓扑结构在物理学中普遍存在，出现在宇宙学、粒子物理和凝聚态物理等领域。它们可以表现出惊人的持久性，因为它们的特征是守恒的拓扑电荷。超流体，如稀薄气体玻色-爱因斯坦凝聚体，为在高度受控的环境中研究这些激发提供了新的令人兴奋的机会。超流体的基本对称性(和磁相)决定了它可以支持什么类型的拓扑激发。这个实验研究项目考察了自旋1和自旋2的玻色-爱因斯坦凝聚体中的三维拓扑激发，包括单极、纽结和Skyrmions。自旋1号实验将探索激发态产生后的时间演化。自旋2实验将从创建和探索各种可用磁相允许的拓扑激发开始，并回答关于它们的时间演化的类似问题。激发将通过将凝聚体暴露在随时间变化的磁场和光场中而产生，随后将通过使用现有的成像技术仔细检查超流体来表征。预计这些结果将直接有助于我们对拓扑激发的科学理解，这些激发涉及物理学中的许多分支。该科学计划还将加强尖端实验研究与本科教育之间的关系，为几名积极进取的本科生以及一名研究生研究人员提供技术和科学培训机会。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Humans have long had a fascination with symmetry, a concept familiar to anyone who has glanced in a mirror or contemplated their left and right hands. Indeed, symmetry is a fundamental organizing principle that appears in every scientific discipline. In physics, symmetries often manifest themselves in terms of topology, or the study of how shapes and structures may - or may not - be deformed continuously into one another. Topology has recently emerged as an important and increasingly relevant topic in modern physics, as recognized by the 2016 Nobel Prize. Shared topological features in different physical systems permit complementary studies, even when those systems are extremely different. For example, similar physics can be studied both in giant particle accelerators at the highest energies and in tabletop apparatus at the coldest temperatures. The ultracold environment central to this research is a dilute gas cooled to tens of billionths of a degree above absolute zero, at which point it develops properties that make it into a kind of well-controlled "universe" into which may be summoned analogues of particles that might - or, perhaps more interestingly, might not - appear in the "real" universe. This project will study the creation and time-evolution of these particle-like phenomena, including point-like monopoles and extended particles known as "skyrmions" and "knots." Such experiments can provide insight into the phenomena and behavior of many different topological systems, and contribute to emerging technologies based on their manipulation and control. The scientific program will also enhance the relationship between cutting-edge experimental research and undergraduate education by providing technological and scientific training opportunities for several highly motivated undergraduates, as well as for a graduate student researcher. In these ways it contributes to the education of the next generation of citizen-scientists.Particle-like topological structures are ubiquitous in physics, appearing in cosmology, particle physics, and condensed-matter physics, among others. They can exhibit a surprising degree of persistence, as they are characterized by a conserved topological charge. Superfluids, such as dilute-gas Bose-Einstein condensates, provide new and exciting opportunities to examine these excitations in highly-controlled environments. The underlying symmetries (and magnetic phases) of a superfluid determine what kinds of topological excitations it can support. This experimental research program examines three-dimensional topological excitations within spin-1 and spin-2 Bose-Einstein condensates, including monopoles, knots, and skyrmions. The spin-1 experiments will explore the time evolution of the excitations following their creation. The spin-2 experiments will begin by creating and exploring the topological excitations permitted by the wider variety of available magnetic phases, and answer similar questions about their time-evolution. The excitations will be created by exposing the condensate to time-dependent magnetic and optical fields, and will be subsequently characterized by close examination of the superfluid using established imaging techniques. The results are expected to contribute directly to our scientific understanding of topological excitations across the many branches of physics in which they appear. The scientific program will also enhance the relationship between cutting-edge experimental research and undergraduate education by providing technological and scientific training opportunities for several highly motivated undergraduates, as well as for a graduate student researcher.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.