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The physics of heat conduction in layered, anisotropic crystals is probed by measurements of the cross-plane elastic constant C 33 and thermal conductivity ⌳ of muscovite mica as a function of hydrostatic pressure. Picosecond interferometry and time-domain thermoreflectance provide high-precision measurements of C 33 and ⌳, respectively, of micron-sized samples within a diamond-anvil cell; ⌳ 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 ⌳ can be accounted for by the pressure dependence of the cross-plane sound velocities.

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ZnO quantum dots ͑QDs͒ of controlled sizes have been fabricated by a simple sol-gel method. The blueshift of room-temperature photoluminescence measurement from free exciton transition are observed decreasing with the QD size that is ascribed to the quantum confinement effect. From the resonant Raman scattering, the coupling strength between electron and longitudinal optical phonon, deduced from the ratio of the second-to the first-order Raman scattering intensity, diminishes with reducing the ZnO QD diameter. The size dependence of electron-phonon coupling is principally a result of the Fröhlich interaction.

Iron may critically influence the physical properties and thermochemical structures of Earth's lower mantle. Its effects on thermal conductivity, with possible consequences on heat transfer and mantle dynamics, however, remain largely unknown. We measured the lattice thermal conductivity of lower-mantle ferropericlase to 120 GPa using the ultrafast optical pump-probe technique in a diamond anvil cell. The thermal conductivity of ferropericlase with 56% iron significantly drops by a factor of 1.8 across the spin transition around 53 GPa, while that with 8-10% iron increases monotonically with pressure, causing an enhanced iron substitution effect in the low-spin state. Combined with bridgmanite data, modeling of our results provides a self-consistent radial profile of lower-mantle thermal conductivity, which is dominated by pressure, temperature, and iron effects, and shows a twofold increase from top to bottom of the lower mantle. Such increase in thermal conductivity may delay the cooling of the core, while its decrease with iron content may enhance the dynamics of large low shear-wave velocity provinces. Our findings further show that, if hot and strongly enriched in iron, the seismic ultralow velocity zones have exceptionally low conductivity, thus delaying their cooling.