RAISE-TAQS: Nonlinear Optical Properties and Novel Quantum Phases of Polar Molecules in Optical Lattic

开发新的分子材料依赖于合成成分(分子)并在严格控制的条件下组装它们的能力。物理性质由分子间距、有序度和取向等参数决定。这些参数通常通过自组装固定到平衡晶态，并且只有通过合成一批新的材料才能改变。该奖项支持使用光学捕获方法来制备分子组件的研究，在这种组件中，这些参数可以通过外场进行调节。这种能力将允许以更便宜、更灵活的方式研究固态材料的基本属性。极性分子将被捕获在光学晶格中，模仿固体晶体的分子排列和性质，并利用外部电场进行定向。这种晶格构型使得系统地调整和探索固体的相关性质成为可能。此外，这种方法有可能探索新的量子现象，如集体光学响应，在这样的系统中。在未来，这项研究有可能为真正的分子材料的合成提供信息，从分子晶体到纳米晶体组装再到金属-有机骨架。它结合了物理学、化学和材料科学的进步，为“晶体工程”提供了一种新的途径。该项目的更广泛影响包括在不同领域的学生培训，包括激光、真空技术和光学设置，以及提供比通常情况下更广泛的跨学科研究体验。最后，定期访问K-12学校，介绍捕获和操纵粒子(例如分子或离子)的实验演示和讲座，将是这项研究的一部分。该项目的主要目标是将极性AlCL分子的量子简并气体加载到光学晶格中，以研究新的量子相并模拟固态晶体材料。这项研究有四个具体目标：第一，精确测量AlCL的能谱和Franck-Condon因子等分子性质；第二，冷却极性AlCL分子到量子简并，并研究偶极玻色-爱因斯坦凝聚体的动力学和稳定性。该小组还将探索由于各向异性偶极-偶极相互作用而产生的相关相，包括液晶和密度波相，并探索低维材料中超流性和电荷有序性之间的相互作用；第三，创建极性分子的一维光学晶格，并通过测量二次谐波来研究其非线性光学响应。通过改变温度和有序度，光学晶格可以从独立的、非相互作用的分子的极限调谐到强关联的一维晶体；第四，通过连续调节晶格参数，利用拉曼散射来探索从非相互作用分子的分子内振动到分子间声子结构的转变。这些实验将证明双原子分子的有序结构可以表现出与固态材料直接相关的现象。这些结果将推动未来的实验，将晶格扩展到二维，最终完全模拟三维晶体系统。它们的低温和可调结构可能会导致全新的现象，如巨大的非线性光学极化率，这可能会激发“晶体工程”领域的新研究方向。该奖项反映了美国国家科学基金会的法定使命，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。

Developing novel molecular materials relies on the ability to synthesize the constituents (molecules) and assemble them under carefully controlled conditions. The physical properties are determined by parameters like the molecular spacing, degree of order, and orientation. These parameters are typically fixed by self-assembly into the equilibrium crystal state and can only be changed by synthesizing a new batch of materials. This award supports research to use optical trapping methods to prepare molecular assemblies where these parameters can be tuned by external fields. This capability will permit the study of basic properties of solid-state materials in a cheaper, more flexible way. Polar molecules will be trapped in optical lattices, mimicking the molecular arrangement and properties of a solid crystal, and be oriented using external electric fields. Such a lattice configuration renders systematic tuning and exploration of relevant properties of solids feasible. Furthermore, this approach has the potential to explore novel quantum phenomena, like collective optical response, in such systems. In the future, this research has the potential to inform the synthesis of real molecular materials, from molecular crystals to nanocrystal assemblies to metal-organic frameworks. It provides a new approach to "crystal engineering" by combining advances in Physics, Chemistry and Materials Science. The project's broader impacts include student training in various areas, including lasers, vacuum technology and optical setups, as well as providing a broader, interdisciplinary research experience than typically accessible. Finally, regular visits to K-12 schools to present experimental demonstrations and lectures on trapping and manipulating particles, e.g. molecules or ions, will be part of this research effort.The main objective of this project is to load a quantum degenerate gas of polar AlCl molecules into an optical lattice to study novel quantum phases and simulate solid-state crystalline materials. This research has four specific goals: First, perform precision measurements of molecular properties, such as the energy spectrum and the Franck-Condon factors of AlCl; Second, cool the polar AlCl molecules to quantum degeneracy and study the dynamics and stability of dipolar Bose-Einstein condensates. The group will also explore correlated phases due to the anisotropic dipole-dipole interaction, including liquid crystal and density-wave phases, and probe the interplay between superfluidity and charge-ordering in low-dimensional materials; Third, create a one-dimensional optical lattice of polar molecules and study its non-linear optical response by measuring the second harmonic generation. By varying temperature and ordering, the optical lattice can be tuned from the limit of independent, noninteracting molecules to a strongly correlated one-dimensional crystal; Fourth, use Raman scattering to explore the transition from intramolecular vibrations of noninteracting molecules to intermolecular phonon structure by continuously tuning the lattice parameters. The experiments will demonstrate that ordered structures of diatomic molecules can exhibit phenomena that are directly relevant to solid-state materials. These results will motivate future experiments to expand the lattice to two dimensions and finally to fully mimic three-dimensional crystal systems. Their low temperature and tunable structure could lead to totally new phenomena, like giant nonlinear optical susceptibilities, that could inspire new research directions in the field of "crystal engineering".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.