The Origins of the Evolution of Thermal Conductivity of Perovskite Superlattices

Abstract

The thermal conductivities of (SrTiO3)n/(CaTiO3)n and other such superlattices have been measured for several layer thicknesses, revealing a trend that dips to a minimum and then rises as the interface density approaches the unit-cell scale. We employ density-functional-theory (DFT)-based machine-learning molecular-dynamics simulations to investigate the thermal conductivities in (SrTiO3)n/(CaTiO3)n superlattices, examining how interface phonons influence the thermal and vibrational properties for n = 1, 2, 4, 6, and 8. The simulations reproduce the thermal conductivity trends with n values and reveal the absence of true interfacial phonons in SL1 and SL2. This study sheds light on the potential for tailoring thermal transport in nanoscale materials by understanding and manipulating the role of interface-specific phonons in superlattices.