Unraveling the Regimes of Interfacial Thermal Conductance at a Solid/Liquid Interface

The interfacial thermal conductance at a solid/liquid interface (G) exhibits an exponential-to-linear crossover with increasing solid/liquid interaction strength, previously attributed to the relative strength of solid/liquid to liquid/liquid interactions. Instead, using a simple Lennard-Jones setup, our molecular simulations reveal that this crossover occurs due to the onset of solidification in the interfacial liquid at high solid/liquid interaction strengths. This solidification subsequently influences interfacial energy transport, leading to the crossover in G. We use the overlap between the spectrally decomposed heat fluxes of the interfacial solid and liquid to pinpoint when "solid-like energy transport" within the interfacial liquid emerges. We also propose a novel decomposition of G into (i) the conductance right at the solid/liquid interface and (ii) the conductance of the nanoscale interfacial liquid region. We demonstrate that the rise of solid-like energy transport within the interfacial liquid influences the relative magnitude of these conductances, which in turn dictates when the crossover occurs. Our results can aid engineers in optimizing G at realistic interfaces, critical to designing effective cooling solutions for electronics among other applications.