A spin-boson thermal rectifier
  Rectification of heat transfer in nanodevices can be realized by combining the system inherent anharmonicity with structural asymmetry. we analyze this phenomenon within the simplest anharmonic system -a spin-boson nanojunction model. We consider two variants of the model that yield, for the first time, analytical solutions: a linear separable model in which the heat reservoirs contribute additively, and a non-separable model suitable for a stronger system-bath interaction. Both models show asymmetric (rectifying) heat conduction when the couplings to the heat reservoirs are different. 
Dvira Segal and Abraham Nitzan