Finite-size Scaling of Four Helium Near the Superfluid Transition and Two-Dimensional Behavior of Three Helium in Four Helium Films

液氦在低温下显示出许多有趣的性质。 温度 有些是这种量子流体所独有的， 与其他系统相同，但可观察到更高程度的 氦气的精确度 他们一直在研究批判行为 在氦的极限超流转变时， 局限于如此小的尺寸，它不再表现为一个 三维系统 他们发明了一种技术 将氦限制在两个间隔良好的硅晶片之间。 他们报告了1999年首次测量超流体密度的结果。 当我们接近超流体转变时， 偏离了三维的行为， 变成二维的 他们建议继续这些 下一个供资期的调查以及开始 测量热容量。 这些数据将提供严格的 有限尺寸标度理论和维数的检验 交叉。 在低温下，他们研究了超流体 4He与3He作为杂质的近单层膜的过渡。 他们报告说，观察到这些电影的过渡 进入超流体状态分两步进行 他们 将其解释为地表形成的标志 为3He。 他们建议继续进行这些测量 研究与相变相关的其他现象， 3He的流体动力学质量。

Liquid helium displays a number of interesting properties at low temperatures. Some are unique to this quantum fluid, others are common to other systems, but observable with a higher degree of precision in helium. They have been studying critical behavior at the superfluid transition in the limit where helium is confined to such small dimensions that it no longer behaves as a three dimensional system. They have devised a technique for confining the helium between two well-spaced silicon wafers. They report first measurements of the superfluid density in which, as one approaches the superfluid transition, the helium deviates from three-dimensional behavior and then crosses over into two dimensions. They propose to continue these investigations for the next funding period as well as to start measurements of heat capacity. These data will provide stringent tests of finite-size scaling theories and dimensionality crossover. At low temperatures they have studied the superfluid transiton of near-monolayer films of 4He with 3He as an impurity. They report the observation that the transition of these films into the superfluid state takes place in two steps. They interpret this as a signature of the formation of the surface state for 3He. They propose to continue with these measurements to study other phenomena associated with the phase transition and the hydrodynamic mass of 3He.