  Interfacial thermal transport is critical for many thermal-related
applications such as heat dissipation in electronics. While the total
interfacial thermal conductance (ITC) can be easily measured or calculated, the
ITC spectral mapping has been investigated only recently and is not fully
understood. By combining nonequilibrium molecular dynamics simulations and
atomistic Green's function method, we systematically investigate the ITC
spectrum across an ideal interface, i.e., the argon-heavy argon interface. Our
results show that the ITC spectrum increases gradually with temperature as more
phonons and anharmonic scattering channels are activated, e.g., the vibrations
with frequencies larger than 1 THz can contribute 5% (15%) to the total ITC at
2 K (40 K) through anharmonic phonon scatterings channels. We further find that
the ITC spectrum from the left interfacial Hamiltonian is quite different from
that of the right interfacial Hamiltonian, which stems from the asymmetry of
anharmonic phonon scatterings caused by the dissimilar vibrational property of
the two interfacial contacts. While all the phonons are involved in the
anharmonic scatterings for the heavy argon interfacial Hamiltonian, these
phonons involved in the anharmonic phonon scatterings from the argon
interfacial Hamiltonians are mainly these vibrations with frequency smaller
than 1 THz (i.e., the cut-off frequency of heavy argon). Finally, we find the
quantum effect is important for the ITC spectrum at low temperatures, e.g.,
below 30 K in our systems. Our results here systematically investigate the
influence of anharmonicity, non-homogeneity, and quantum effects on the ITC
spectrum, which is critical for designing and optimizing the interfaces with
better performance.
