Ci. Um et al., THERMAL-CONDUCTIVITY AND FIRST VISCOSITY VIA TEMPERATURE-DEPENDENT ELEMENTARY EXCITATION-SPECTRA IN THIN AND BULK LIQUID-HE-4, Physica. B, Condensed matter, 203(1-2), 1994, pp. 151-168
The coefficients of thermal conductivity (kappa) and first viscosity (
eta) in thin and bulk liquid He-4 are evaluated explicitly as a functi
on of temperature via the zero-temperature and temperature-dependent t
wo- and three-dimensional elementary excitation spectra that are micro
scopic only in the long-wavelength limit. The coefficients kappa(T) an
d eta(T) obtained from the temperature-dependent spectrum have slightl
y larger values than those of the zero-temperature spectrum through th
e whole range of temperatures, while as the temperature approaches abs
olute zero, the coefficients kappa(T) and eta(T) coincide with each ot
her in both spectra. Below about 0.8 K, both coefficients increase exp
onentially with decreasing temperature. At temperatures below about 0.
3 K, kappa(T) in the thin and bulk cases have T-5 and T-6 dependences,
respectively, whereas eta(ph)(T) has a T-1 dependence in both dimensi
ons with extra temperature-dependent terms, which originate from three
-phonon processes for both excitation spectra.