Novel Ferromagnetic Domains and Quantum Criticality with Bose Condensates in a Shaken Optical Lattice

虽然原子长期以来一直被认为是我们所看到的世界和我们生活的环境的基石，但它们在低温下的行为从未停止过让我们感到惊讶。例子包括无摩擦流动的超流体，以及允许读取、写入和存储大量信息的量子磁性材料。首席研究人员最近领导的一项工作表明，当激光来回摇动原子时，超流性和铁磁性(条形磁铁中的磁性类型)同时表现出来，就像乒乓球在湖面上荡漾一样。在原子超流体中观察到的耐人寻味的磁区动力学为在量子区域有效地存储和处理信息提供了新的策略。该项目的主要科学目标是模拟和研究一种新型的二维晶格中的四极磁体，它比传统材料中的两极(南北极)磁体具有更丰富的性质。科学计划得到了S.M.A.R.T.(科学、数学和研究培训)项目下广泛的外展努力的赞扬。当原子超流被转移到由两个垂直光学驻波重叠而产生的二维抖动光学晶格中时，将出现所提出的4极磁相。当震动幅度被小心地调到一个临界值以上时，超流体预计会分裂成4个具有铁磁相互作用的极。将通过原子样品的直接原位成像来检测和研究4极结构域的形成。与传统的双极磁体相比，四极磁体提供了新颖的磁区和顶点结构，并与图论中的四色定理和统计物理中的Potts模型有着独特的联系。此外，铁磁相的相变与各种量子现象有关，包括Rashba超流体、Berezinskii-Kosterlitz-Thouless相变和Kibble-Zurek机制。探索这种量子物理可能会有理论和实践两方面的收获，包括建立一个理解量子临界动力学的理论框架，模拟N极铁磁体，制造可编程的磁性材料，甚至潜在的量子信息存储和处理。

While atoms have been long recognized as the building blocks of the world we see and the environment we live in, their behavior at low temperatures has never ceased to surprise us. Examples include superfluids that flow without friction and quantum magnetic materials that permit read, write and storage of ample information. A recent work led by the principal investigator showed that both superfluidity and ferromagnetism (the type of magnetism in bar magnets) manifest simultaneously in atoms when shaken back and forth by laser beams, like ping-pong balls riding the ripples on a lake. The intriguing dynamics of magnetic domains observed in the atomic superfluids suggests new strategies to efficiently store and process information in the quantum regime. The major science goal of this project is to simulate and study a new type of 4-pole magnet in a two-dimensional lattice, which promises much richer properties than the 2-pole (south and north pole) magnetism in conventional materials. The science program is complimented by an extensive outreach effort under the S.M.A.R.T. (Science, Mathematics, And Research Training) project. The proposed 4-pole magnetic phase will arise when an atomic superfluid is transferred into a two-dimensional shaken optical lattice, generated by overlapping two perpendicular optical standing waves. When the shaking amplitude is carefully tuned above a critical value, the superfluid is anticipated to split into 4 poles with ferromagnetic interactions. The formation of the 4-pole domain will be detected and studied by direct in situ imaging of the atomic sample. Compared to the conventional 2-pole magnets, the 4-pole magnets offer novel domain and vertex structures and are uniquely related to the four-color theorem in graph theory and the Potts model of statistical physics. Furthermore the phase transition into the ferromagnetic phase is associated with a variety of quantum phenomena, including Rashba superfluids, the Berezinskii-Kosterlitz-Thouless transition, and the Kibble-Zurek mechanism. Exploration of this quantum physics may have both academic and practical payoffs, including the development of a theoretical framework to understand quantum critical dynamics, simulations of N-pole ferromagnetic magnets, fabrication of programmable magnetic materials, and potentially even quantum information storage and processing.