Negative differential thermal resistance in one-dimensional hard-point gas models

We study negative differential thermal resistance (NDTR) of one-dimensional hard-point gas models. The models are non-integrable unless all particles have the same mass. We show that NDTR can exist in both the integrable case and the non-integrable case. In the integrable case, the existence of NDTR is analytically predicted and numerically confirmed and a mechanism for NDTR different from that observed in lattice models is unveiled. In the non-integrable case, we show that the mechanism also works under certain conditions and the properties of NDTR are found to depend on the particle masses and the system size by the molecular dynamics simulations. These results shed new light on the mechanisms for NDTR and may help design new functional heat devices.