Search for the minimum thermal conductivity in mixed cryocrystals (CH4)1−ξKrξ

The isochoric thermal conductivity of (CH4)1−ξKrξ solid solutions is studied between 40 K and ∼150 K over a wide range of concentrations (ξ=0.013, 0.032, 0.07, 0.115, 0.34, 0.71, 0.855, 0.937, and 0.97). A gradual transition from the thermal conductivity of a highly perfect crystal to the minimum thermal conductivity is observed as the crystal becomes increasingly more disordered. A qualitative description is given in the framework of Debye model of thermal conductivity, which takes into consideration the fact that phonon mean free path cannot decrease indefinitely.