RUI: Topological Excitations in Spinor Bose-Einstein Condensates

长久以来，人类对对称性有着浓厚的兴趣，任何一个看过镜子或观察过自己左右手的人都很熟悉这个概念。事实上，对称性是一个基本的组织原则，出现在每一个科学学科。在物理学中，对称性通常表现在拓扑学方面，或者是研究形状和结构如何可以-或可以不-连续变形成另一个。拓扑学最近成为现代物理学中一个重要且日益相关的主题，并获得2016年诺贝尔奖的认可。不同物理系统共有的拓扑特征允许互补研究，即使这些系统非常不同。例如，类似的物理学既可以在最高能量的巨型粒子加速器中进行研究，也可以在最冷温度的桌面设备中进行研究。这项研究的核心超冷环境是一种被冷却到绝对零度以上数十亿分之一度的稀释气体，在这一点上，它发展出一些性质，使其成为一种控制良好的“宇宙”，可以召唤出可能--或者更有趣的是，可能不会--出现在“真实的”宇宙中的粒子的类似物。这个项目将研究这些粒子现象的产生和时间演化，包括点状单极子和被称为“skyrmions”和“knots”的扩展粒子。“这样的实验可以提供对许多不同拓扑系统的现象和行为的洞察，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性很高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，加强前沿实验研究与本科教育之间的关系。粒子拓扑结构在物理学中无处不在，出现在宇宙学、粒子物理学和凝聚态物理学等领域。它们可以表现出令人惊讶的持久性，因为它们的特征是保守的拓扑电荷。超流体，如稀释气体玻色-爱因斯坦凝聚，提供了新的和令人兴奋的机会，检查这些激发在高度受控的环境。超流体的基本对称性（和磁相）决定了它可以支持什么样的拓扑激发。这个实验研究计划检查自旋1和自旋2玻色-爱因斯坦凝聚体，包括单极子，结和skyrmion内的三维拓扑激发。自旋-1实验将探索激发产生后的时间演化。自旋-2实验将开始通过创建和探索拓扑激发所允许的更广泛的各种可用的磁性相位，并回答类似的问题，他们的时间演变。激发将通过将冷凝物暴露于随时间变化的磁场和光场来产生，随后将通过使用已建立的成像技术对超流体进行仔细检查来表征。预计这些结果将直接有助于我们对拓扑激发在物理学的许多分支中出现的科学理解。该科学计划还将通过为几名积极进取的本科生和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生教育之间的关系。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。

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.