Violation of Fourier's law and anomalous heat diffusion in silicon nanowires

We study heat conduction and diffusion in silicon nanowires (SiNWs) systematically by using non-equilibrium molecular dynamics. It is found that the thermal conductivity (kappa) of SiNWs diverges with the length as, kappa proportional to L-beta, even when the length is up to 1.1 mu m which is much longer than the phonon mean free path. The dependences of beta on temperature and length are also discussed. Moreover, an anomalous heat diffusion is observed which is believed to be responsible for the length dependent thermal conductivity. Our results provide strong evidence that Fourier's law of heat conduction is not valid in low-dimensional nanostructures. (C) 2010 Elsevier Ltd. All rights reserved.