Second-sound velocity and superfluid density in $sup 4$He under pressure near T/sub lambda/
Second-sound velocity and superfluid density in $sup 4$He under pressure near T/sub lambda/
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$sup 4$He 在 T/sub lambda/ 附近压力下的第二声速和超流体密度
DOI：
10.1103/physreva.7.2145
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发表时间：
1973
影响因子：
2.9
通讯作者：
G. Ahlers
中科院分区：
文献类型：
--
作者：
D. Greywall;G. Ahlers
在超流体He 4中，当温度≥1.6 K时，测量了蒸汽压与熔化压之间的第二声速。特别强调了T λ附近的温度区域，2× 10−5 > ε≡1−T T λ (P) > 10−2。利用这些结果，其他已有的热力学信息，以及线性双流体流体力学，确定了超流体分数ρ s ρ。小ε处的高压数据表明，沿等压线的ρ s ρ不能用ε的幂定律来描述。相反，幂律项的奇异修正比ε阶的修正大得多。因此，结果拟合为ρ s ρ= k (P) ε ζ [1+ a (P) ε y]。他们得出了0.66±ζ±0.68和0.4±y±0.6，与压强p无关。这些指数的结果，以及奇异修正的存在，与标度、通用性和最近的显式计算是一致的。
The velocity of second sound was measured in superfluid He 4 between vapor pressure and the melting pressure for T≥ 1.6 K. Particular emphasis was given to the temperature region near T λ with 2× 10− 5≲ ε≡ 1− T T λ (P)≲ 10− 2. Using these results, other existing thermodynamic information, and linear two-fluid hydrodynamics, the superfluid fraction ρ s ρ was determined. The higher-pressure data at small ε revealed that ρ s ρ along isobars cannot be described by a pure power law in ε. Instead, singular corrections to the leading power-law term exist which are much larger than of order ε. Therefore, the results were fitted to the expression ρ s ρ= k (P) ε ζ [1+ a (P) ε y]. They yielded 0.66≲ ζ≲ 0.68 and 0.4≲ y≲ 0.6, independent of the pressure P. These results for the exponents, and the existence of singular corrections, are consistent with scaling, universality, and recent explicit calculations.