Thermal conductivity in one-dimensional nonlinear disordered lattices: Two kinds of scattering effects of hard-type and soft-type anharmonicities

Abstract: The amorphous solids can be theoretically modeled by anharmonic disordered lattices. However, most of theoretical studies on thermal conductivity in anharmonic disordered lattices only focus on the potentials of hard-type (HT) anharmonicity. Here we study the thermal conductivity $\kappa$ of one-dimensional (1D) disordered lattices with both hard- and soft-type (ST) anharmonic on-site potentials. It is found, via both direct molecular dynamic simulations and theoretical method, that the anharmonicity dependence of $\kappa$ in the HT model is nonmonotonous, while in the ST model is monotonously increased. This provides a new way to enhance thermal conductivity in disordered systems. Furthermore, $\kappa$ of the HT model is consistent with the prediction of the quasi-harmonic Green-Kubo (QHGK) method in a wide range of anharmonicity, while for the ST model, the numerical results seem largely deviated from the theoretical predictions as the anharmonicity becomes soft. This new and peculiar feature of the ST model may root in the fact that only delocalization effect exists, different from the competing roles that both delocalization and localization play in the counterpart HT model.