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: 2008
• 资助国家: 加拿大
• 起止时间: 2008-01-01 至 2009-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=389003
• 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年在激光冷却的碱原子中发现了Bose-Einstein凝结（BEC）以来（经过数十年的努力），全世界都在全球范围内就超速原子和超低物质的特性进行了研究。 BEC涉及占据相同单粒子量子状态的宏观数量的原子，从而导致超流体特性（持续的电流，量化涡流等），这是在超级流体中发现的类似物和超导体中发现的类似物。    我目前的研究涉及在存在Feshbach共振的情况下捕获的费米气体，这使人们可以“调整” S波散射长度的大小和符号（这完全描述了在超低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变得非常大，所以人们可以在有限温度下探测两流体流体动力学，在1941年在超氟液体HE的情况下首先由Landau进行研究。 Landau两流体方程应描述整个BCS-BEC交叉的动力学（从Cooper对的BCS凝结到真实分子的BEC）。我的工作涉及对两流体集体振荡的详细研究（在均匀的玻色超流体中的第一和第二声音的类似物）。具有Feshbach共振的超流体费米气体使我们首次探究被困的量子气体的局部平衡区域，即使密度仍然很小，碰撞起着至关重要的作用。在捕获的费米超级流体气体中对两流体行为的实验性观察将是1938年液态氦中超流体的历史观察结果的完全类似物，尽管由于不同的热力学，量子气体的量子性质在量子气体中会大不相同。