Anharmonic quantum thermal transport across a van der Waals interface

We investigate the anharmonic phonon scattering across a weakly interacting interface by developing a quantum mechanics-based theory. We find that the contribution from anharmonic three-phonon scatterings to interfacial thermal conductance can be cast into Landauer formula with transmission function being temperature-dependent. Surprisingly, in the weak coupling limit, the transmission due to anharmonic phonon scattering is unbounded with increasing temperature, which is physically impossible for two-phonon processes. We further reveal that the anharmonic contribution in a real heterogeneous interface (e.g., between graphene and monolayer molybdenum disulfide) can dominate over the harmonic process even at room temperature, highlighting the important role of anharmonicity in weakly interacting heterogeneous systems. Impact statement Two-dimensional (2D) van der Waals heterostructures that are built by vertically stacking different 2D materials not only serve as a new platform for exploring new materials physics, but also open up enormous possibilities for applications, such as in nanoelectronic and photonic devices. Because each layer in such heterostructures acts both as a bulk and an interface, this construct can have limited thermal transport across the layers, and yet our understanding on heat dissipation in such systems is still limited due to quantum effect and phononic anharmonicity. Here, we develop a quantum-mechanical theory to describe thermal conduction across such systems by considering interlayer phonon scatterings and placing both harmonic and anharmonic scattering under the same framework. We apply the theory to explore the thermal transport across different heterostructures and reveal the following findings: (1) The contribution of three-phonon processes can be cast into Landauer form with the transmission function being temperature-dependent. (2) The transmission of three-phonon processes is unbounded and increases linearly with temperature in the high temperature limit. (3) The anharmonic contribution in real heterostructures (e.g., graphene-MoS _2 ) can dominate over the harmonic contribution even at room temperature, highlighting the important role of anharmonicity in weakly interacting heterogeneous systems. Graphical Abstract