Abstract
In this paper we consider a bipartite system composed of two subsystems each coupled to its own thermal environment. Based on a collision model, we mainly study whether the approximation (i.e., the inter-system coupling is ignored when modeling the system–environment interaction) is valid or not. We also address the problem of heat transport unitedly for both excitation-conserving system–environment interactions and non-excitation-conserving system–environment interactions. For the former interaction, as the inter-system interaction strength increases, at first this approximation gets worse as expected, but then counter-intuitively gets better even for a stronger inter-system coupling. For the latter interaction with asymmetry, this approximation gets progressively worse. In this case we realize a perfect thermal rectification, and we cannot find an apparent rectification effect for the former interaction. Finally and more importantly, our results show that whether this approximation is valid or not is closely related to the quantum correlations between the subsystems, i.e., the weaker the quantum correlations, the more justified the approximation and vice versa.
Highlights
CiccarelloIn most practical situations, a quantum system inevitably interacts with its environment, which induces decoherence and dissipation [1]
Why can the decoupling approximation give a good estimate of heat current and steady state even for a large δ ? In References [71,72], it was found that the compositeness is closely related to the quantum correlations between the constituent particles
Based on the collision model, we mainly study whether the decoupling approximation is valid or not for describing the nonequilibrium dynamics
Summary
A quantum system inevitably interacts with its environment, which induces decoherence and dissipation [1]. In Reference [3], the local description for two coupled quantum nodes may predict heat currents from a cold to a hot thermal reservoir, or the existence of currents even in the absence of a temperature gradient. The origin of these effects, as discussed in References [5,23], lies in the fact that there is an external work cost related to the breaking of global detailed balance. Inspired by the previous work on the local and global master equations, we consider an decoupling approximation within the framework of collision model, environment acts on subsystem without considering the inter-system coupling, i.e., ignores the direct coupling between the subsystems when modeling the system–environment interaction. We find that whether or not this decoupling approximation is valid is closely related to the quantum correlations between the subsystems
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