Thermal Expansion Coefficient and Universality Near the Superfluid Transition of 4He under Pressure

  • K. H. Mueller
  • F. Pobell
  • Guenter Ahlers


Recent measurements1 of the specific heat Cp of pressurized liquid helium near the λ-line gave results which seemed to be in conflict with the concept of universality;2 specifically the amplitude ratio A/A’ of the singular part of Cp above and below Tλ appeared to depend upon the pressure P.1 We report on new determinations of A/A’ for 4He near Tλ based upon measurements of the isobaric thermal expansion coefficient ßp 3, which is a linear function of Cp sufficiently near Tλ . Our measurements were made by a new technique, to be described in detail elsewhere,3 which is characterized by high pressure stability (ΔP/P ≲ 2.10−8), and temperature resolution (ΔT/T ≈ 2·10−7). Our experiment covered the ranges 5 bar ≤ P ≤ 29 bar, and 2·10−5 ≤ |t| ≤ 0.07, where t = T/Tλ − 1. The data were fit to
$$ {\beta _p} = (A/\alpha ) {t^{ -\alpha }}[1 + D {t^x}] + B $$
for T > Tλ, and simultaneously to the same function with primed coefficients for T < Tλ.


Thermal Expansion Quantum Statistics Theoretical Prediction Excellent Agreement Thermal Expansion Coefficient 
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Copyright information

© Plenum Press, New York 1975

Authors and Affiliations

  • K. H. Mueller
    • 1
  • F. Pobell
    • 1
  • Guenter Ahlers
    • 2
  1. 1.Institut für Festkörperforschung KernforschungsanlageJülichW. Germany
  2. 2.Bell LaboratoriesMurray HillUSA

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