Spin-boson thermal rectifier.

TLDR: This work considers two variants of the anharmonic system-a spin-boson nanojunction model that yield analytical solutions: a linear separable model in which the heat reservoirs contribute additively, and a nonseparable model suitable for a stronger system-bath interaction.

Abstract: The heat conduction properties of nanojunctions attract attention for two reasons. First, heating in nanoconductors, a crucial issue for their operation and stability, is determined by both heat release and conduction in such systems. Secondly, as with electronic conduction, the restrictive geometry raises fundamental questions concerning the relationship between transport processes in microscopic systems and their macroscopic counterparts. Indeed thermal transport properties of nanowires can be very different from the corresponding bulk properties as is demonstrated by the recent confirmation [1] of the prediction [2] that the low temperature ballistic phonon conductance in a one-dimensional quantum wire is characterized by a universal quantum unit. Also of considerable interest are studies that confront the macroscopic Fourier law, J � � KrT, that connects the heat current J to the temperature gradient rT and defines the thermal conductance K, with heat transport on the microscopic scale. Harmonic chains were repeatedly discussed theoretically in these contexts and considerable experimental progress was also made [1]. For reviews see Refs. [3,4]. An intriguing mode of behavior of transport devices is current rectification, allowing larger conduction in one direction than in the opposite one when driven far enough from equilibrium. Such phenomena were extensively studied for electronic conduction in molecular junctions, but much less so for thermal nanoconductors. For a harmonic thermal conductor connecting (by linear coupling) two [left (L), right (R)] harmonic thermal reservoirs that are maintained at equilibrium with the temperatures TL and TR, respectively, heat transfer is a ballistic process and the heat current J can be recast into a Landauer-type expression [2] J �