  Thermal transport through liquid-solid interfaces plays an important role in
many chemical and biological processes, and better understanding of
liquid-solid energy transfer is expected to enable improving the efficiency of
thermally driven applications. We determine the spectral distribution of
thermal current at liquid-solid interfaces from nonequilibrium molecular
dynamics, delivering a detailed picture of the contributions of different
vibrational modes to liquid-solid energy transfer. Our results show that
surface modes located at the Brillouin zone edge and polarized along the
liquid-solid surface normal play a crucial role in liquid-solid energy
transfer. Strong liquid-solid adhesion allows also for the coupling of in-plane
polarized modes in the solid with the liquid, enhancing the heat transfer rate
and enabling efficient energy transfer up to the cut-off frequency of the
solid. Our results provide fundamental understanding of the energy transfer
mechanisms in liquid-solid systems and enable detailed investigations of energy
transfer between, e.g., water and organic molecules.
