Quantum Fluids in One and Two Dimensions

这是一个低温物理研究项目。液态He-3和液态He-4是表现出宏观量子行为的范例系统，分别服从费米统计和玻色统计。虽然人们已经对这些量子液体进行了大量的研究，但在吸附在表面的He-3和He-4原子薄膜中仍发现了有趣的结果。最近的测量发现，He-3原子倾向于漂浮在He-4薄膜的顶部，并将相分离为二维汽相和液态。计划进行热容测量以阐明这种相分离/转变的性质，以确定这个本质上的量子系统是否也是著名的Onsager的2D Ising模型的物理实现。核磁共振和热容测量将研究吸附在MCM-41上的He-3和He-4的性质。MCM-41是一种高度多孔的衬底，一维孔直径为2.5至5.0 nm，长度可达500 nm。这些测量的结果将与一维量子系统的理论进行对比测试。参与这些实验的本科生和研究生接受了低温、高真空和超灵敏电子测量方面的严格培训。他们必须整合这些技能来完成要求苛刻的实验，这一过程将迅速而优雅地为他们在政府、工业和学术界的职业生涯做好准备。这是一个低温物理项目。当温度降低时，所有物质都冻结成固体。液体He-3和He-4除外，它们在绝对零度下仍保持液态。究其原因，与量子测不准原理有关。虽然化学成分相同，但He-3的原子核中有一个中子和两个质子，而He-4的原子核中各有两个。所有的原子要么是费米子，要么是玻色子，这取决于它们拥有的中子、质子和电子的总数。这条规则使得He-3是费米子，He-4是玻色子，因此，液体He-3和液体He-4的行为截然不同，特别是当这些“量子流体”被强迫进入至少一个维度是“纳米”的体积时。该项目致力于了解一维和二维费米子和玻色子系统的性质，即限制在原子薄膜中的He-3和He-4原子，或直径在2.5至5.0纳米范围内的一维微孔中的He-3和He-4。我们在研究这些量子液体中获得的知识有助于理解超导体和其他电子系统。参与这些实验的本科生和研究生接受了低温、高真空和超灵敏电子测量方面的严格培训。他们必须整合这些技能，以完成要求苛刻的实验，这一过程将迅速而优雅地为他们在政府、行业和学术界的职业生涯做好准备。

This is a low temperature physics research project. Liquid He-3 and liquid He-4 are paradigm systems that exhibit macroscopic quantum behavior, obeying respectively Fermi and Bose statistics. While a great deal has been learned about these quantum liquids in bulk, fascinating results are still being discovered in atomically thin films of He-3 and He-4 adsorbed on surfaces. Recent measurements found that He-3 atoms tend to float on top of a He-4 film and phase separate into 2-dimensional vapor and liquid phases. Heat capacity measurements are planned to elucidate the nature of this phase separation/transition to determine whether this intrinsically quantum system is also a physical realization of the celebrated 2D Ising model of Onsager. Nuclear magnetic resonance and heat capacity measurements will study the properties of He-3 and He-4 adsorbed in MCM-41, a highly porous substrate with one dimensional pores of 2.5 to 5.0 nm in diameter and up to 500 nm in length. Results of these measurements will be tested against the theories of one dimensional quantum systems. Undergraduate and graduate students involved in these experiments receive rigorous training in cryogenic, high vacuum and ultrasensitive electronic measurements. They must integrate these skills to complete demanding experiments, a process that quickly and elegantly prepares them for careers in government, industry and academe.This is a low temperature physics project. All substances freeze into solid when the temperature is reduced. The exceptions being liquid He-3 and He-4, which remain liquid even at absolute zero. The reason for this is related to the quantum uncertainty principle. Although chemically identical, He-3 has one neutron and two protons in its nucleus and He-4 has two of each. All atoms are either Fermion or Boson depending on the total number of neutrons, protons and electrons they have. This rule makes He-3 a Fermion and He-4 a Boson, and as a consequence, liquid He-3 and liquid He-4 behave quite differently, particularly when these "quantum fluids" are forced into volumes where at least one dimension is "nanoscopic". This project seeks to understand the properties of one and two-dimensional Fermion and Boson systems, namely He-3 and He-4 atoms confined in atomically thin films, or in tiny one-dimensional pores, with diameters in the range 2.5 to 5.0 nanometers. The knowledge we gain in studying these quantum liquids contributes to the understanding of superconductors and other electronic systems. Undergraduate and graduate students involved in these experiments receive rigorous training in cryogenic, high vacuum and ultrasensitive electronic measurements. They must integrate these skills to complete demanding experiments, a process that quickly and elegantly prepares them for careers in government, industry and academe.