Rectification of heat currents across nonlinear quantum chains: A general approach beyond weak coupling

Within the emerging field of quantum thermodynamics the issues of heat transfer and heat rectification are basic ingredients for the understanding and design of quantum heat engines. Here, a general approach is developed which is not plagued by deficiencies of conventional weak coupling treatments, allows to cover broad ranges of parameter space, and is applicable to various realizations including the presence of disorder and external time-dependent fields. As a particular application one-dimensional chains of anharmonic oscillators terminated by thermal reservoirs are analyzed and the basic mechanism for the occurrence of rectification is identified. The efficiency of the method opens a door to treat also rather long chains and extensions to higher dimensions and geometries.