Negative differential thermal resistance in a two-dimensional gas model

The negative differential thermal resistance (NDTR) effect refers to a phenomenon that may take place in a heat transport system where the heat current counterintuitively decreases as the temperature difference between heat baths increases. Understanding and controlling the NDTR properties of out-of-equilibrium systems and using them to design new functional thermal devices are the major challenges of modern science and technology, which has important theoretical significance and application prospects. Up to now, the various lattice models representing solid materials have been taken to study the NDTR properties, but the fluid models have not received enough attention. It has recently been shown that in one-dimensional hard-point gas models representing fluids, there is a mechanism for NDTR induced by heat baths. The mechanism for NDTR in such a system depends on the simple fact that decreasing the temperature of the cold bath can weaken the motion of particles and decrease the collision rate between particles and the hot bath, thus impeding thermal exchange between the cold and hot baths. In this paper, we study how this mechanism works in more general two-dimensional gas models described by multi-particle collision dynamics. The gas models we consider are in a finite rectangular region of two-dimensional space with each end in contact with a heat bath. Based on the analytical results and numerical simulations, we show that the mechanism underlying NDTR induced by heat baths is also in effect for two-dimensional gas models and is applicable for describing systems with small sizes and weak interactions. Our result, together with that previously obtained in one-dimensional gas models, provides strong evidence that gas systems can exhibit NDTR by decreasing the temperature of the heat bath, which sheds new light on the exploring direction for developing various fluidic thermal control devices.