Quantum Phases of Rotating Multipolar Molecules

加州大学伯克利分校的Birgitta Whaley获得了化学系化学理论、模型和计算方法项目的一项奖励，该项目使用基态量子蒙特卡罗技术研究多极分子形成的新量子相。 Whaley教授和她的研究小组研究偶极和四极分子的密度，其中相互作用为能量提供了显着的各向异性取向贡献，从而产生了强相互作用的量子分子系统。 他们的目标是确定这些系统的行为和性质，特别注意在确定简并量子区域中的量子性质时平移和旋转自由度之间的相互作用，即，在尽可能低的温度下。 他们正在使用由研究人员和她的同事开发的新的路径积分基态量子蒙特卡罗代码，该代码将完整的旋转和平移自由度与高精度的“任何阶”传播子结合起来。 新的高精度旋转/平移代码允许探索这些系统的新化学和物理学，而不限制偶极取向，并允许计算非对角矩阵元素，从而可以研究分子系统中的大规模量子相干性，这使他们能够首次研究分子旋转如何改变众所周知的偏离，量子气体和流体中平移自由度的对角长程序。 最近的实验方法的发展，不仅探测和揭示量子相的微观行为，而且还能够在费曼最初的量子模拟意义上模拟新的相，这使得新分子量子相的理论研究成为不久的将来化学物理景观的重要组成部分。这项研究将分子化学与量子物理学结合在一起，将分子化学的领域扩展到强量子体系中的冷分子。 因此，它体现了作为21世纪科学研究的一个重要方面的跨学科科学观。 预期的结果为生物和新型凝聚相材料的量子模拟奠定了基础，并揭示了创造具有定制量子特性和不同应用的不寻常材料的机会。这项研究涉及化学和物理学的学生，并将与伯克利校园的教育和推广活动联系起来。

Birgitta Whaley of the University of California, Berkeley, is supported by an award from the Chemical Theory, Models and Computational Methods program in the Chemistry division to use ground state Quantum Monte Carlo techniques for the study of novel quantum phases formed by multipolar molecules. Professor Whaley and her research group study dipolar and quadrupolar molecules at densities where the interactions provide significant anisotropic orientational contributions to the energy, resulting in strongly interacting quantum molecular systems. Their goal is to determine the behavior and properties of these systems with special attention to the interplay between translational and rotational degrees of freedom in determining the quantum properties in the degenerate quantum regime, i.e., at the lowest possible temperatures. They are using a new path integral ground state Quantum Monte Carlo code developed by the researcher and her coworkers that incorporates full rotational and translational degrees of freedom with a high accuracy "any order'' propagator. The new high accuracy rotation/translation code allows exploration of the novel chemistry and physics of these systems without constraints on dipole orientation and allows calculation of off-diagonal matrix elements giving access to study of large scale quantum coherences in molecular systems, allowing them to investigate for the first time how molecular rotations might modify the well-known off-diagonal long range order of translational degrees of freedom in quantum gases and fluids. Recent growth of experimental methods that not only probe and reveal the microscopic behavior of quantum phases but also enable emulation of new phases in Feynman's original sense of quantum simulation, which makes theoretical research in novel molecular quantum phases an essential component of the chemical physics landscape for the near future. This research brings together molecular chemistry with quantum physics to extend the realm of molecular chemistry to cold molecules in strongly quantum regimes. It thus embodies the interdisciplinary view of science that is an essential aspect of scientific research in the twenty-first century. The anticipated results form a base for quantum simulation of biological and novel condensed phase materials and reveal opportunities for creating unusual materials with tailored quantum properties and diverse applications. The research involves students from chemistry and physics, and will be linked to education and outreach activities on the Berkeley campus.