Thermally driven classical Heisenberg chain with a spatially varying magnetic field: Thermal rectification and Negative differential thermal resistance

Thermal rectification and negative differential thermal resistance are two important features that have direct technological relevance. In this paper, we study the classical one dimensional Heisenberg model, thermally driven by heat baths attached at the two ends of the system, and in presence of an external magnetic field that varies monotonically in space. Heat conduction in this system is studied using a local energy conserving dynamics. It is found that, by suitably tuning the spatially varying magnetic field, the homogeneous symmetric system exhibits both thermal rectification and negative differential thermal resistance. Thermal rectification, in some parameter ranges, shows interesting dependences on the average temperature T and the system size N - rectification improves as T and N is increased. Using the microscopic dynamics of the spins we present a physical picture to explain the features observed in rectification as exhibited by this system and provide supporting numerical evidences. Emergence of NDTR in this system can be controlled by tuning the external magnetic field alone which can have possible applications in the fabrication of thermal devices.