Cepellotti A Fugallo G Paulatto L Lazzeri M Mauri F Marzari N 2015 The conduction of heat in two dimensions displays a wealth of fascinating phenomena of key relevance to the scientific understanding and technological applications of graphene and related materials. Here, we use density-functional perturbation theory and an exact, variational solution of the Boltzmann transport equation to study fully from first-principles phonon transport and heat conductivity in graphene, boron nitride, molybdenum disulphide and the functionalized derivatives graphane and fluorographene. In all these materials, and at variance with typical three-dimensional solids, normal processes keep dominating over Umklapp scattering well-above cryogenic conditions, extending to room temperature and more. As a result, novel regimes emerge, with Poiseuille and Ziman hydrodynamics, hitherto typically confined to ultra-low temperatures, characterizing transport at ordinary conditions. Most remarkably, several of these two-dimensional materials admit wave-like heat diffusion, with second sound present at room temperature and above in graphene, boron nitride and graphane. application/pdf https://sonar.ch/global/documents/163066 eng info:eu-repo/semantics/altIdentifier/doi/10.1038/ncomms7400 info:eu-repo/semantics/altIdentifier/pmid/25744932 info:eu-repo/semantics/openAccess Nature communications. - 2015 Phonon hydrodynamics in two-dimensional materials. http://purl.org/coar/resource_type/c_6501