Non-Monotonic Thickness Dependent Hydrodynamic Phonon Transport in Layered Titanium Trisulphide: First-Principles Calculation and Improved Callaway Model Fitting
Abstract
Different from diffusive and ballistic phonon transport, the hydrodynamic phonon transport has many unique thermal properties such as super-linearity dependence of thermal conductivity on width and macroscopic phonon motion. In this work, the thickness dependent hydrodynamic phonon transport in layered titanium trisulphide (TiS3) is investigated by first-principles calculation and improved Callaway model. From the picture of linearized phonon Boltzmann transport based on first-principles calculation, two indicators at 100 K clearly show the existence of hydrodynamic phonon transport: the displaced phonon distribution with a constant drift velocity regardless of phonon wavevector and phonon polarization as well as the much larger N scattering rates than U scattering rates. The extracted drift velocity decreases significantly from 1954 m/s to 241 m/s under a temperature gradient 107 K/m as the temperature increases from 50 K to 100 K. From the improved Callaway model, the hydrodynamic phonon transport has a non-monotonic dependence on thickness due to the competition between phonon-phonon scattering and phonon-boundary scattering. The non-monotonic dependence can better understand the phonon properties of hydrodynamic transport and help design materials to observe hydrodynamic phonon transport experimentally. The temperature, width and length effects on the phonon transport behavior are also discussed individually.