Size Dependence of the Thermal Conductivity of Helium I Near the<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>λ</mml:mi></mml:math>Point

Abstract

The thermal conductivity of helium I was measured along its vapor pressure curve over the range $3\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}6}\ifmmode^\circ\else\textdegree\fi{}\mathrm{K}&lt;T\ensuremath{-}{T}_{\ensuremath{\lambda}}&lt;1\ifmmode^\circ\else\textdegree\fi{}\mathrm{K}$ using the parallel-plate technique. The exponent in a power-law variation of thermal diffusivity with $T\ensuremath{-}{T}_{\ensuremath{\lambda}}$ was found to depend on the plate spacing. These results could imply the existence of a relatively temperature-independent characteristic length in helium I near ${T}_{\ensuremath{\lambda}}$ approximately ${10}^{4}$ to ${10}^{5}$ times larger than the coherence length.