Strong correlations in multi-component quantum gases

对超冷量子气体中强关联引起的有趣物理效应的研究已经成熟为原子物理和凝聚态物理之间相互联系的一个非常活跃的研究领域。研究单位FOR801正是在这个界面上行动，并为国际发展做出贡献。超冷原子系统中可用的特殊控制允许实现大量最初在固体物理背景下引用的哈密顿模型。利用粒子相互作用、晶格参数和维度的可调性来制备非常干净、无缺陷的系统，为准确测试处于凝聚态物理核心的潜在理论模型的预测打开了可能性，玻色-哈伯德模型是最突出的例子之一。在Forschergruppe的第一个资助期内，汉堡小组在制备和检测迄今未被探索的强关联量子气体系统方面取得了相当大的进展。能够进入三角形和六边形晶格的强关联区域，以及实现全动量分辨的布拉格光谱来探索和识别新的相和激发是这一领域的两个基本成就。在第二个资助期，我们打算继续研究不同晶格几何和维度的强关联旋量系统和费米-玻色混合物。这项工作将极大地得益于第一阶段取得的实验成果以及与FOR801研究单位理论和实验小组的简明合作。与我们的实验前提和技术相适应的互惠的理论描述的发展构成了一个有希望的基础，以制备、识别和探索正在考虑的多味量子气体系统的更复杂的相。特别是我们将专注于限制在六方光学晶格中的旋量凝聚的物理。我们最近首次研究了一种依赖于磁场的六方晶格结构的有趣方面，因此它是“磁性的”。与自旋相关的局域化和相干的碰撞自旋动力学一起可能会产生有趣的新效应，如依赖于状态的相变，阻止隧穿、自旋纠缠和输运。第一个结果显然推动了对这些系统的进一步研究，并在第二个资助期内深入了解有关量子模拟的基本物理和机会。我们将研究概念上不同于超立方晶格的三角形和六方晶格中的输运性质，作为一个长期目标，我们计划研究六方晶格中更高轨道系统的物理，以保证存在受挫的新相。本项目的第二个中心将是研究光学晶格中费米-玻色混合的新相，作为汉堡小组在第一个资助期所做的实验和理论工作的直接延续。有趣的现象，如电荷密度波的形成或极化子等准粒子的存在，预计将在这些混合系统中发生，并将在本项目的框架内实现和详细研究。在这个研究单位的头三年里，完全动量分辨的布拉格光谱学将作为一种工具，明确地识别这些相关的多体状态。此外，我们计划建立一个新的三光束晶格，类似于用于研究旋量凝聚的晶格，用于费米-玻色实验，以允许在强关联系统的背景下访问迄今未被探索的物理现象，即六角光学晶格中的类石墨素物理。这些研究将与凝聚态物理学中生动讨论的主题非常相似，在凝聚态物理学中，奇异超导态和轨道效应的影响是最令人感兴趣的。作为一个长期目标，我们在旋量BEC领域的深刻经验应该扩展到自旋变化动力学，以及更广泛的光学晶格中费米子系统的自旋相关现象。

The investigation of intriguing physical effects provoked by strong correlations in ultracold quantum gases has matured into a very active field of research at the interlink between atomic and condensed matter physics. The Research Unit FOR801 precisely acts at this interface and contributes to the international development.The exceptional control available in systems of ultracold atoms allows for the realization of a whole wealth of model Hamiltonians often originally invoked in the context of solid state physics. The opportunity to prepare very clean, defect-free systems in hand with the tunability of particle interaction, lattice parameters and dimensionality opens up the possibility to accurately test predictions of underlying theoretical models which are at the heart of condensed matter physics, the Bose-Hubbard model being one of the most prominent examples.Within the first funding period of this Forschergruppe considerable progress in preparing and detecting thus far unexplored strongly correlated quantum gas systems has been obtained in the Hamburg group. The ability to enter the regime of strong correlations in triangular and hexagonal lattice geometries as well as the implementation of fully momentum-resolved Bragg spectroscopy to explore and identify novel phases and excitations are two of the fundamental achievements in this context.In the second funding period we intend to continuatively investigate strongly correlated Spinor systems as well as Fermi-Bose mixtures in different kinds of lattice geometries and dimensionalities. This work will greatly benefit from the experimental achievements obtained in the first period and the concise collaboration with the theory and experimental groups in the Research Unit FOR801. Mutually beneficial development of theoretical descriptions suiting our experimental preconditions and techniques constitute a promising basis to prepare, identify and explore more complex phases of the multi-flavour quantum gas systems under consideration.In particular we will focus on the physics of Spinor condensates confined in a hexagonal optical lattice. We have recently investigated for the very first time the interesting aspects of an mF-dependent thus “magnetic” hexagonal lattice structure. Spin-dependent localization together with coherent collisional spin dynamics might give rise to interesting new effects like state-dependent phase transitions, a blockade of tunnelling and spin entanglement and transport. The first results clearly motivate to further study these systems and to obtain an in-depth understanding of the underlying physics and opportunities concerning quantum simulations within the second funding period. Transport properties in triangular and hexagonal lattices which are expected to be conceptually different from hyper- cubic lattices will be investigated and as a long-term goal we plan to study the physics of higher orbital system in hexagonal lattices promising the existence of frustrated new phases.A second central point within this project will be the investigation of novel phases of Fermi-Bose mixtures in optical lattices as a direct continuation of the experimental and theoretical work performed by the Hamburg group in the first funding period. Interesting phenomena such as the formation of charge density waves or the existence of quasi-particles such as polarons are predicted to occur in these mixed systems and shall be realized and studied in detail in the framework of this project. Fully momentum-resolved Bragg spectroscopy incorporated in the first three years of this Research Unit will serve as a tool to unambiguously identify these correlated many-body states. Furthermore we plan to set up a new three beam lattice, similar to that used to study Spinor condensates, for the Fermi-Bose experiment to grant access to thus far unexplored physical phenomena in the context of strongly correlated systems, i.e. grapheme-like physics in a hexagonal optical lattice. These investigations will be in close analogy to topics vividly discussed in condensed matter physics where exotic superconducting states and the influence of orbital effects are of highest interest. As a long-term goals our profound experience in the field of Spinor BEC shall be extended to spin-changing dynamics and more generally spin-dependent phenomena of fermionic systems in optical lattices.