Optics

Physics

Ceramic

Composite material

Nanotechnology

Thin film

Scattering

Dopant

Materials science

Phonon

Condensed matter physics

Titanate

Strontium titanate

Thermal diffusivity

Atmospheric temperature range

Doping

Thermal conductivity

Thermodynamics

Physical Review Letters

We present a study of thermal conductivity, κ, in undoped and doped strontium titanate in a wide temperature range (2-400 K) and detecting different regimes of heat flow. In undoped SrTiO_{3}, κ 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 SrTi_{1-x}Nb_{x}O_{3}, 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 (τ_{p}=(ℏ/k_{B}T)).

Thermal Transport and Phonon Hydrodynamics in Strontium Titanate