  We investigate the influence of three- and four-phonon scattering,
perturbative anharmonic phonon renormalization, and off-diagonal terms of
coherent phonons on the thermal conductivity of CsPbBr3 phase change
perovskite, by using advanced implementations and first-principles simulations.
Our study spans a wide temperature range covering the entire structural
spectrum. Notably, we demonstrate that the interactions between acoustic and
optical phonons result in contrasting trends of phonon frequency shifts for the
high-lying optical phonons in orthorhombic and cubic CsPbBr3 as temperature
varies. Our findings highlight the significance of wave-like tunneling of
coherent phonons in ultralow and glass-like thermal conductivity in halide
perovskites.
