Thermal resistance below the superfluid transition of4He in a heat current

Abstract

We report on the thermal resistivity of4He nearT λ in heat currents 20≲Q≲300 μW/cm 2. The temperature at the bottom of a layer was measured as a function of that at the top and compared with integrations of models for the conductivity λ(Q,t). The data reveal a new dissipative region belowTλ(Q) with a small but finite resistivity and a sharp onset which can not be explained by the usual “mutual friction” due to vortices.