Dynamics and Excitations of Spin-Orbit-Coupled Bose-Einstein Condensates

量子多体相互作用决定了材料的性质，如磁性和导电性。了解这些特性如何取决于材料的结构、温度和材料中的电子运动，对于开发新技术非常重要，例如那些使用超导或“自旋电子学”的技术。本项目将研究在激光合成势中使用超冷原子的模型系统中的多体相互作用。激光将耦合原子的运动和“自旋”，从而产生自旋-轨道耦合（SOC），类似于许多电子材料中重要的相对论SOC效应。本项目将重点研究SOC如何影响原子玻色-爱因斯坦凝聚体（BEC）中的量子输运现象和集体激发。BEC是量子气体中在足够低的温度下发生的相干超流体相。了解SOC如何影响BEC中的自旋输运将为设计新的“自旋电子”器件提供有益的指导，这些器件旨在利用自旋（量子力学角动量）以比当前基于电荷的电子器件更高的效率和更低的能耗来携带和处理信息。这项研究将带来新的见解，帮助科学家理解和发现新型超流体和超导体，在这些超流体和超导体中，不同自旋的粒子之间的相互作用很重要。该项目还将加强该研究组与活跃在该领域的几位理论家之间的合作，并培养物理和工程专业的学生参与涉及原子物理、量子物理、凝聚态物理和光学的跨学科研究。该实验研究项目将研究原子（Rb-87）玻色-爱因斯坦凝聚体（BEC）受光学（拉曼）合成规范场和自旋轨道耦合（SOC）的影响。重点研究自旋轨道耦合（SOC） BEC中的量子动力学、输运和激发。该研究建立在该团队最近的成就基础上，包括在SOCBEC中修饰带之间演示可调谐Landau-Zener跃迁，实现Landau-Zener- Stueckelberg干涉（准动量空间中的原子干涉测量），以及利用调制拉曼耦合诱导的“第二代修饰带”实现具有新型自旋动量锁定的新型SOC。目前的计划将特别研究各种自旋相关的输运和激发。一个例子是“自旋偶极子模式”（交变自旋电流），它不仅可以用来探测自旋输运，还可以探测在这种集体激励存在下的SOCBEC的碰撞和热化。另一个例子是所谓的剪刀模式和自旋-剪刀模式，可用于探测超流动性以及如何通过SOC和合成磁场对其进行修饰。该计划的后期还将通过添加光学晶格来研究低维（特别是一维）SOC BEC，其中SOC有望产生更明显的影响（例如改变基态，相互作用和激发）。这项工作可能为设计新的物质状态（拓扑相、新型超流体）和理解SOC系统中的自旋输运和动力学提供见解，这在自旋电子学中是重要的。

Quantum many-body interactions are responsible for material properties such as magnetism and conductivity. Understanding how these properties depend on a material's structure, its temperature, and the motion of electrons in the material is important for developing new technologies, for example those using superconductivity or "spintronics". This project will investigate many-body interactions in model systems using ultracold atoms in synthetic potentials generated by laser light. Lasers will couple the motion and "spin" of atoms, to cause spin-orbit-coupling (SOC) analogous to the relativistic SOC effects that are important in many electronic materials. This project will focus on the experimental studies of how SOC affects quantum transport phenomena and collective excitations in an atomic Bose-Einstein condensate (BEC). A BEC is a coherent superfluid phase that occurs at sufficiently low temperatures in a quantum gas. Understanding how SOC affects spin transport in BEC will provide helpful guidance for designing novel "spintronic" devices that aim to use spin (quantum mechanical angular momenta) to carry and process information with much higher efficiency and lower energy consumption than current charge-based electronics. The study will lead to new insights that will help scientists understand and discover new types of superfluids and superconductors in which the interaction of particles of different spins are important. This project will also enhance collaborations between this experimental group and several theorists active in the field, and train students in physics and engineering to participate in interdisciplinary research involving atomic physics, quantum physics, condensed matter physics, and optics.This experimental research program will study an atomic (Rb-87) Bose-Einstein condensate (BEC) subject to optically (Raman) generated synthetic gauge fields and spin-orbit coupling (SOC). The study will focus on quantum dynamics, transport and excitations in spin-orbit-coupled (SOC) BEC. The study builds upon the team's recent achievements including the demonstration of a tunable Landau-Zener transition between the dressed bands in SOCBEC, and the realization of the Landau-Zener- Stueckelberg interference (atom interferometry in quasi-momentum space) and a new type of SOC with novel spin-momentum locking using "2nd generation dressed bands" induced by modulated Raman coupling. The current program will study in particular various spin-dependent transport and excitations. One example is the "spin dipole mode" (alternating spin current) that can be used to probe not only the spin transport but also collisions and thermalization of SOCBEC in the presence of such collective excitations. Another example is the so called scissors mode and spin-scissors mode that can be used to probe superfluidity and how it may be modified by SOC and synthetic magnetic fields. The later part of the program will also investigate low-dimensional (especially 1D) SOC BEC by adding an optical lattice, where the SOC is expected to have even more pronounced effects (such as to alter the ground state, interactions and excitations). This work may provide insights to engineer new states of matter (topological phases, novel superfluids) and to understand the spin transport and dynamics in SOC systems, which are important in spintronics.