Experiments with Quantum Gases of Lithium in 1, 2, and 3 Dimensions

随着捕获、冷却和操纵原子气体的能力的迅速发展，对超冷原子气体的研究已经大大扩展，以便它们可以被应用于更好地理解凝聚态、材料、核和粒子物理中的复杂现象。原子气体可以冷却到纳米开尔文状态，在这种状态下，原子的行为更像波，而不是经典粒子。在这种“量子机制”中，原子表现出一些在物理世界中已知的最令人震惊的现象，包括超流性，这是一种类似超导的现象，但用中性原子取代了电子。与具有缺陷、杂质和随机无序的真实材料不同，原子模拟本质上是干净的，并且非常可调，能够对基本模型进行高度可控的测试。根据这项拨款进行的实验将使用超冷费米子锂原子Li-6来模拟高温超导体的性质和特征，高温超导体是具有重大技术意义的材料，但仍只有部分了解。该小组还将继续研究具有不同自旋数的混合物配对，以绘制出这个极其丰富的系统的相图。一个特别的焦点是“FFLO”阶段，在这个阶段，配对发生时质心动量不为零。FFLO相的理论研究由来已久，但到目前为止还没有明确的实验观测结果。这些实验有望澄清观察到的相分离与其他实验的不同。最后，利用锂的玻色子形式Li-7，该小组将研究安德森定域化，即由于无序而从超流体或导体到绝缘体的转变。玻色子系统的第二个实验将探索最近提出的用于首次创建二维孤子的动态稳定方案。这项工作的更广泛的影响是两方面的：首先，更多地了解材料的基本模型，可能使设计出性能更好的真实材料，如更高温度的超导体；其次，这项研究将为从事这项工作的学生和博士后科学家提供广泛的科学培训。

Research with ultracold atomic gases has greatly expanded by rapid advancement in the ability to trap, cool, and manipulate atomic gases, so that they may be applied to gain better understanding of complex phenomena in condensed matter, material, nuclear, and particle physics. Atomic gases can be cooled to the nano-Kelvin regime where atoms behave more as waves than as classical particles. In this "quantum regime," the atoms exhibit some of the most startling phenomenon known in the physical world, including superfluidity, an analog of superconductivity but with neutral atoms taking the place of electrons. Unlike real materials that possess defects, impurities, and random disorder, the atomic analogs are inherently clean and extraordinarily tunable enabling highly controllable tests of fundamental models. The experiments performed under this grant will use ultra-cold Fermionic lithium atoms, Li-6, to simulate the properties and characteristics of high-temperature superconductors, which are materials of great technological significance, but remain only partially understood. The group will also continue their studies of pairing of mixtures with unequal spin numbers to map out the phase diagram of this incredibly rich system. A particular focus is the "FFLO" phase, where pairing occurs with non-zero center of mass momentum. The FFLO phase has been long studied theoretically, but as of yet there are no clear experimental observations. These experiments will hopefully clarify differences in observations of phase separation with other experiments. Finally using a Bosonic form of lithium, Li-7, the group will investigate Anderson localization, the transition from a superfluid or conductor to an insulator due to disorder. A second experiment in the Boson system will explore a recently proposed dynamical stabilization scheme for creating two-dimensional solitons for the first time.The broader impact of this work is two-fold: firstly, greater understanding of fundamental models of materials may enable the design of real materials with improved performance, such as higher temperature superconductors; and secondly, this research will provide a broad scientific training for the students and post-doctoral scientists engaged in it.