How does collective hydrodynamic phonon transport impact interfacial thermal conductance

Interfacial thermal conductance (ITC) at nanoscale interfaces is a central fundamental problem involving symmetry breaking, and becomes also a critical bottleneck for the near-junction thermal management of next-generation micro- and nano-electronics. Collective phonon hydrodynamic transport in materials is the thermal counterpart of superfluid transport, however its impact on thermal transport across an adjacent interface remains an open question. Here we answer this question via a mesoscopic theoretical framework based on a direct solution of Boltzmann transport equation with an interfacial transmission model considering phonon branch conversion and the first-principles inputs. Our results unexpectedly show that collective phonon transport significantly reduces ITC origining from the competition between the larger interfacial temperature jump due to phonon non-equilibrium and the enhanced heat flow. The temperature and isotope concentration are also shown to significantly impact the ITC reduction due to their influence on the hydrodynamic window. Furthermore, we unravel that collective phonon transport still reduces the total thermal resistance of heterostructures from the dominant enhanced intrinsic transport over the reduced interfacial counterpart. This work thus provides fundamental understanding of the impact of phonon hydrodynamics on interfacial thermal resistance, and opens a new avenue for the manipulation and optimization of transistor-scale heat dissipation of nanoelectronics.