Thermal Transport and Phonon Hydrodynamics in Strontium Titanate

• Published in: Physical review letters 2018-03, Vol.120 (12), p.125901-125901, Article 125901
• Main Authors: Martelli, Valentina, Jiménez, Julio Larrea, Continentino, Mucio, Baggio-Saitovitch, Elisa, Behnia, Kamran
• Format: Article
• Language: English
• Subjects: Acoustic velocity; Dopants; Fluid dynamics; Fluid flow; Heat conductivity; Heat transfer; Heat transmission; Hydrodynamics; Laminar flow; Momentum; Phonons; Physics; Strontium titanates; Temperature; Thermal conductivity; Thermal diffusivity
• ISSN: 0031-9007; 1079-7114
• DOI: 10.1103/physrevlett.120.125901

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)).