Abstract
We present a study of thermal conductivity, , in undoped and doped strontium titanate in a wide temperature range (2–400 K) and detecting different regimes of heat flow. In undoped , evolves faster than cubic with temperature below its peak and in a narrow temperature window. Such behavior, previously observed in a handful of solids, has been attributed to a Poiseuille flow of phonons, expected to arise when momentum-conserving scattering events outweigh momentum-degrading ones. The effect disappears in the presence of dopants. In , a significant reduction in lattice thermal conductivity starts below the temperature at which the average inter-dopant distance and the thermal wavelength of acoustic phonons become comparable. In the high-temperature regime, thermal diffusivity becomes proportional to the inverse of temperature, with a prefactor set by sound velocity and Planckian time ().
- Received 7 December 2017
DOI:https://doi.org/10.1103/PhysRevLett.120.125901
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