Magnetic Excitations in Magnetically Ordered Superfluids

该项目支持研究一种新的“超流体”（一种旋量玻色-爱因斯坦凝聚体），它不仅流动无阻力（超流体的特征之一），而且还呈现磁性秩序（像条形磁铁）。这种超流体是由原子气体组成的，它被冷却到极低的温度，并被所谓的“光镊子陷阱”（由激光产生）限制在真空室中。该项目支持的研究人员将研究这种气体材料的磁性特征，并阐明这种材料的磁性和超流动性相互影响的方式。这项工作的更广泛的目标是帮助更好地理解材料，特别是那些量子力学理论起主导作用的材料（这些材料可以被越来越多地投入使用，特别是当它们涉及短长度尺度时，如微电子工业）。为了实现这一目标，这里研究的磁性超流体是一个有用的测试对象，人们相信，材料性质背后的所有基本物理学都是已知的，并且可以应用非常精确和敏感的测量技术。该项目将在一所公立大学进行，并将支持在这种环境下培训研究生。该项目侧重于三个具体目标。首先是表征磁有序超流体中的磁振子。这些磁振子是这些材料的基本磁激发。各种方法，许多基于直接成像的传播磁振子波，将用于测量磁振子能量，阻尼，磁矩，和非线性，也阐明了远距离磁偶极子相互作用的作用。本项目的第二个目的是研究铁磁超流体中磁振子的凝聚，这与固态磁性材料中的磁振子凝聚现象有关。第三个目的是研究空间变化磁化强度（自旋织构）对质量电流和自旋电流的影响。这项工作将研究标量超流体和磁有序超流体之间的差异，目的是确定旋量玻色-爱因斯坦凝聚体流体动力学的基本过程（有人可能称之为“超流体磁流体动力学”）。

This project supports the study of a new kind of "superfluid" (a spinor Bose-Einstein condensate) which not only flows without resistance (one of the characteristics of superfluids) but also presents magnetic order (like a bar magnet). This superfluid is made up of an atomic gas that is cooled to extremely low temperatures and confined by a so-called "optical tweezer trap" (created by laser light) within a vacuum chamber. The researchers supported by this project will examine the magnetic characteristics of this gaseous material, and also clarify ways in which the magnetism and superfluidity of this material influence one another. The broader goal of this work is to help understand materials better, in particular those materials where the theory of quantum mechanics plays a dominant role (such materials can be expected to be increasingly put to use, particularly when they involve short length scales such as in the microelectronics industry). Toward this goal, the magnetic superfluid studied here is a useful test subject, one for which all of the basic physics underlying the material properties is believed to be known, and to which one can apply very precise and sensitive measurement techniques. The project will take place at a public University, and will support the training of graduate students in that setting.The project is focused on three specific aims. The first is to characterize magnons in magnetically ordered superfluids. These magnons are the elementary magnetic excitations of these materials. A variety of approaches, many based on directly imaging the propagation of magnon waves, will be used to measure the magnon energy, damping, magnetic moment, and nonlinearities, and also to clarify the role of long-range magnetic dipole interactions. The second aim of this project is to study the condensation of magnons within ferromagnetic superfluids, related to the phenomenon of magnon condensation in solid-state magnetic materials. The third aim is to study the influence of spatially varying magnetization (spin textures) on mass currents and spin currents. This work will study differences between the study of scalar superfluids and magnetically ordered superfluids, with the goal of identifying the basic processes in the hydrodynamics of spinor Bose-Einstein condensates (something one might call "superfluid magnetohydrodynamics").