  By way of the non-equilibrium Green's function simulations and analytical
expressions, the quantum thermal conductance of stanene is studied. We find
that, due to the existence of Dirac fermion in stanene, the ratio of electron
thermal conductance and electric conductance becomes a
chemical-potential-dependent quantity, violating the Wiedemann-Franz law. This
finding is applicable to any two-dimensional (2D) materials that possess
massless Dirac fermions. In strong contrast to the negligible electronic
contribution in graphene, surprisingly, the electrons and phonons in stanene
carry a comparable heat current. The unusual behaviours in stanene widen our
knowledge of quantum thermal transport in 2D materials.
