Predicting the thermal conductivity in a graphene nanoflake from its response to a thermal impulse

Inspired by pulsed laser-assisted thermal relaxation experiments, we simulated the response of a nanometer-size monolayer graphene sample to thermal impulses by means of nonequilibrium molecular dynamics. By following the time evolution of the temperature profile until equilibrium is eventually reached, we obtain a direct estimation of the thermal conductivity of the excited graphene sample. It is shown that the predicted thermal conductivity depends on which vibrational degrees of freedom are in fact excited by the thermal impulse, suggesting that its determination depends, among many other issues, on the actual phonon population generated in the sample. The situation here explored is typically found in experiments or simulations addressing a transient regime of approach to equilibrium.