Theory of trapped superfluid fermi gases

俘获超流体费米气体理论

• 批准号: 4620-2006
• 负责人: Griffin, Allan
• 金额: $ 3.06万
• 依托单位: University of Toronto
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2007
• 资助国家: 加拿大
• 起止时间: 2007-01-01 至 2008-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=364250
• 关键词: Theory; trapped; superfluid; fermi; gases

Since the dramatic discovery in 1995 of Bose-Einstein condensation (BEC) in laser-cooled alkali atoms (after decades of effort), there has been a worldwide explosion of research on the properties of ultracold atoms and ultracold matter.  BEC involves a macroscopic number of atoms occupying the same single-particle quantum state, which results in superfluid properties (persistent currents, quantized vortices, etc.) which are the analogue of those found in superfluid He and superconductors.        My current research deals with trapped Fermi gases in the presence of a Feshbach resonance, which allows one to "tune" the size and sign of the s-wave scattering length (which completely describes the interatomic interaction at ultracold temperature).  Because the interaction can be made very large in these Fermi gases, one can probe the two-fluid hydrodynamics at finite temperatures, first studied by Landau in 1941 in the context of superfluid liquid He.  The Landau two-fluid equations should describe the dynamics across the entire BCS-BEC crossover (going from a BCS condensate of Cooper pairs to a BEC of real molecules).  My work involves a detailed study of the two-fluid collective oscillations (the analogue of first and second sound in a uniform Bose superfluid).  Superfluid Fermi gases with a Feshbach resonance allow us for the first time to probe the local equilibrium region of trapped quantum gases where collisions play a crucial role, even though the density is still extremely small.  Experimental observation of two-fluid behaviour in trapped Fermi superfluid gases would be the complete analogue of the historic observations in 1938 of superfluidity in liquid Helium, although the detailed properties will be quite different in quantum gases because of the different thermodynamics.

自1995年激光冷却碱金属原子中的玻色-爱因斯坦凝聚（BEC）被发现以来，世界范围内对超冷原子和超冷物质性质的研究迅速发展。BEC涉及宏观数量的原子占据相同的单粒子量子态，导致超流性质（持续电流、量子化涡旋等）。这是在超流氦和超导体中发现的类似物。 我目前的研究是在存在费什巴赫共振的情况下处理被囚禁的费米气体，这使得人们可以“调整”s波散射长度的大小和符号（它完全描述了超冷温度下的原子间相互作用）。因为在这些费米气体中可以使相互作用非常大，所以可以探测有限温度下的双流体流体动力学，首先由朗道在1941年在超流液体He的背景下研究。朗道双流体方程应该描述整个BCS-BEC交叉的动力学（从库珀对的BCS凝聚到真实的分子的BEC）.我的工作涉及到两流体集体振荡的详细研究（均匀玻色超流体中第一和第二声音的模拟）。具有Feshbach共振的超流体费米气体使我们首次能够探测被捕获的量子气体的局部平衡区域，在该区域中碰撞起着至关重要的作用，尽管密度仍然非常小。实验观察到两个-被俘获的费米超流气体中的流体行为将完全类似于1938年对液氦中超流性的历史性观察，尽管由于热力学的不同，量子气体的具体性质会有很大的不同。