Pressure tuning of the thermal conductivity of the layered muscovite crystal

The physics of heat conduction in layered, anisotropic crystals is probed by measurements of the cross-plane elastic constant C₃₃ and thermal conductivity Λ of muscovite mica as a function of hydrostatic pressure. Picosecond interferometry and time-domain thermoreflectance provide high-precision measurements of C₃₃ and Λ, respectively, of micron-sized samples within a diamond-anvil cell; Λ changes from the anomalously low value of 0.46 W m^-1 K^-1 at ambient pressure to a value more typical of oxides crystals with large unit cells, 6.6 W m^-1 K^-1, at P=24 GPa. Most of the pressure dependence of Λ can be accounted for by the pressure dependence of the cross-plane sound velocities.