Extended multi-temperature model for electron–phonon coupling and ultrafast thermal transport in graphene

Ultrafast thermal transport in low-dimensional materials challenges traditional diffusive models due to reduced scattering, strong electron–phonon coupling, and pronounced non-equilibrium effects. To address these complexities, we extend the macroscopic multi-temperature model by incorporating non-diffusive and non-local phenomena, treating electrons, optical phonons, and acoustic phonons as coupled but thermally distinct subsystems. We benchmark this enhanced framework against the multi-temperature Boltzmann transport equation, enabling detailed resolution of branch-dependent energy relaxation and identifying bottlenecks in thermalization. This approach provides a more accurate and comprehensive description of heat flow in emerging materials, offering novel insights into phonon dynamics and electron–phonon interactions. These theoretical advances pave the way for the improved design and optimization of next-generation nanoelectronic and photothermal devices.