Exploring Ultracold Matter Along the Complexity Axis

将普通物质置于特殊环境中可以创造出令人着迷的新现象和物理学应用。例如，人们在一段时间前就意识到，某些气体可以降低到绝对零度略高一点的温度，但不会凝结成液滴。这一新的超冷气体学科使人们对简单原子集合的量子力学行为有了丰富的新认识。现在，一组新的实验试图通过引入具有内部复杂性的原子和分子来丰富这一学科。这样做将导致在理解和控制化学反应方面出现前所未有的细节，应用还没有梦想。令人惊讶的是，在某些情况下，它还将允许人们对宇宙的基本规则有更深刻的理解，甚至比最大的粒子加速器都能提供。为了进行这样的实验，有必要彻底了解复杂的超冷气体的动力学。这项工作将探索复杂性在气体中的作用，考虑诸如基本热力学等现象，在这些现象中，热或声音的传播可能在不同方向上不同，或者可能取决于(并因此揭示)化学反应。它还将考虑一种可能性，即气体中的分子可以在短暂的时间内相互粘在一起，这是推测的，但尚未得到证实。在利用超冷气体应用之前，必须彻底了解这种自粘性气体的特性。为此，这项工作将详细研究量子混沌在两体碰撞动力学中的作用。已经证明，或者至少怀疑，在镧系二聚体原子和碱性二聚体分子的超冷碰撞中存在混沌。已经采取了第一步，但还必须进行全面的分析，包括能级和共振宽度的统计分布以及磁场的影响。这种分析将使用不同复杂程度的模型来进行，以揭示现象的基本物理学。此外，虽然偶极原子和分子的微分散射截面是已知的，但它们对气体热力学的完全影响在很大程度上仍未被探索。超冷偶极气体的动力学将使用蒙特卡罗计算进行。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Placing ordinary matter in extraordinary circumstances can create fascinating new phenomena and applications in physics. For example, it was realized some time ago that certain gases could be reduced to temperatures just a tiny bit above absolute zero, but without condensing into liquid drops. This new discipline of "ultracold" gases has led to a wealth of new understanding of quantum mechanical behavior of collections of simple atoms. Now, a new set of experiments seeks to enrich this discipline by introducing atoms and molecules with internal complexity. Doing so will lead to unprecedented detail in understanding and controlling chemical reactions, with applications yet to be dreamed of. Amazingly, it will in certain cases also allow for a deeper understanding of the fundamental rules of the universe than even the largest particle accelerator can provide. To carry out such experiments, it is necessary to thoroughly understand the dynamics of a complex, ultracold gas. This work will explore the role of complexity in the gas, considering phenomena such as basic thermodynamics, in which the propagation of heat or of sound can be different in different directions, or may depend on (and thus reveal) chemical reactivity. It will also consider the possibility, conjectured but not yet demonstrated, that molecules in the gas can stick to each other for brief amounts of time. Properties of this self-adhesive gas must be thoroughly understood before ultracold gases can be harnessed for applications. To do so, the work will investigate in detail the role of quantum chaos in the two-body collision dynamics. Chaos has already been demonstrated, or at least suspected, in ultracold collisions of lanthanide dimer atoms as well as alkali dimer molecules. The first steps have been taken, but a complete analysis, including the statistical distributions of energy levels and resonance widths, as well as the influence of magnetic fields, must still be undertaken. This analysis will be carried out using models of various degrees of complexity, to reveal the essential physics of the phenomena. Moreover, while the differential scattering cross sections of dipolar atoms and molecules are known, their complete influence on the thermodynamics of the gas remains largely unexplored. Dynamics of an ultracold dipolar gas will be undertaken, using Monte Carlo calculations.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.