Revisiting phonon transport in perovskite SrTiO3: Anharmonic phonon renormalization and four-phonon scattering

We investigate the role of anharmonic phonon renormalization and four-phonon scattering in the thermal transport of cubic SrTiO3 from 200 to 800 K by constructing an accurate first-principles machine-learning potential with active learning. The anharmonic phonon dispersion relations show obvious low-frequency phonon hardening as temperature increases, implying potential importance of fourth order lattice anharmonicity in cubic SrTiO3. Under the perturbation theory and Boltzmann transport equation scheme, we find that phonon frequency renormalization can make a significant improvement in the calculations of thermal conductivity and its temperature dependence of cubic SrTiO3 compared to experimental data. Four-phonon scattering is usually important in strongly anharmonic materials with ultralow thermal conductivity and simple crystals featured by large acoustic-optical phonon band gaps. Nonetheless, we find that four-phonon scattering can make a considerable contribution to suppressing phonon transport in cubic SrTiO3 which has a moderate thermal conductivity. This study deepens the understanding of anharmonic phonon renormalization and four-phonon scattering in oxide perovskites.

Automated summary

By constructing an accurate potential function with machine learning, the study investigates the roles of anharmonic phonon renormalization and four-phonon scattering in the thermal transport of cubic SrTiO3. The findings suggest that four-phonon scattering plays a significant role in suppressing phonon transport in the material.