Quantum Hydrodynamics in Interacting Fermi Gases

相互作用费米气体中的量子流体动力学

• 批准号: 1404135
• 负责人: John Thomas
• 金额: $ 53.75万
• 依托单位: North Carolina State University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-08-01 至 2017-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1404135&HistoricalAwards=false
• 关键词: Quantum; Hydrodynamics; Interacting; Fermi; Gases

This project explores the nearly perfect fluid-flow properties of a special class of ultra-cold atoms, Fermi gases, which are tightly confined in a bowl made of laser light and cooled to temperatures just billionths of a degree above absolute zero. The bowl is turned off to release the ultra-cold atoms into a high vacuum and they are imaged during expansion by laser flash-photography. By just turning a knob in these tabletop experiments, an expanding atom cloud can be made to simulate the behavior of electrons in superconductors, neutrons in neutron stars, or even an exotic state of matter that existed just microseconds after the Big Bang. The study of these nearly perfect fluids has practical significance in testing theories of high temperature superconductors, which will one day enable energy-saving power transmission, and fundamental significance in testing theories of perfect fluid flow that may have occurred just after the Big Bang. The goal of this project is to measure precisely the nearly perfect hydrodynamic transport properties of an ultra-cold atomic Fermi gas. Spin-up and spin-down atoms are made to strongly interact by means of a bias magnetic field, tuned near a collisional (Feshbach) resonance. A collision between two such clouds produces shock waves as the strongly-interacting clouds bounce off each other. Measurements of the shear viscosity above, at, and below resonance will enable new tests of the lower bound predicted for a perfect fluid using string theory methods. Studies of scale-invariant flow at resonance will determine the bulk viscosity and test general predictions for scale invariant systems. The experiments cross interdisciplinary boundaries by testing state-of-the-art theory for the transport properties of strongly-correlated matter, which can be simulated in these cold atom experiments, such as high-temperature superconductors, nuclear matter, and quark-gluon plasmas that are created in heavy ion collisions.

该项目探索了一类特殊的超冷原子费米气体的近乎完美的流体流动特性，费米气体被紧紧地限制在一个由激光制成的碗中，并被冷却到比绝对零度高十亿分之一度的温度。碗被关闭，将超冷原子释放到高真空中，它们在膨胀过程中通过激光闪光照相术成像。在这些桌面实验中，只需转动一个旋钮，就可以制造出一个膨胀的原子云来模拟超导体中的电子、中子星中的中子，甚至是大爆炸后几微秒内存在的奇异物质状态。 对这些近乎完美的流体的研究在测试高温超导体理论方面具有实际意义，这将有一天能够实现节能电力传输，并且在测试大爆炸后可能发生的完美流体流动理论方面具有根本意义。该项目的目标是精确测量超冷原子费米气体的近乎完美的流体动力学输运性质。自旋向上和自旋向下的原子通过偏置磁场进行强烈的相互作用，该偏置磁场在碰撞（Feshbach）共振附近调谐。 两个这样的云之间的碰撞会产生冲击波，因为强烈相互作用的云会彼此反弹。测量的剪切粘度以上，在和以下的共振将使新的测试的下限预测一个完美的流体使用弦理论的方法。 研究尺度不变的流动在共振将确定整体粘度和测试一般的预测尺度不变的系统。这些实验通过测试强相关物质的输运特性的最新理论来跨越跨学科的界限，这些理论可以在这些冷原子实验中模拟，例如高温超导体，核物质和重离子碰撞中产生的夸克胶子等离子体。