Phonon–phonon scattering selection rules and control: an application to nanofriction and thermal transport

Phonon–phonon scattering processes are the crucial phenomena which account for phonon decay, thermal expansion, heat transfer, protein dynamics, spin relaxation and related quantities. In this work, we show how the symmetries of the system determine which scattering processes are allowed at any order of anharmonic approximation, irrespective of the chemical composition. We also discuss how to control the system symmetries to switch on and off any single scattering process. We apply the presented results to the study and control of nanoscale intrinsic friction and thermal transport in lamellar van der Waals transition metal dichalcogenides. Thanks to its general formulation, the presented framework expands the materials science tool set for the design of nanoengineered thermally-active materials, irrespective of the specific chemical composition and atomic topology.