
Quantum heat current under nonperturbative and nonMarkovian conditions: Applications to heat machinesQuantum heat current under nonperturbative and nonMarkovian conditions: Applications to heat machines 
"/Kato, Akihito/"Kato, Akihito ,
"/Tanimura, Yoshitaka/"Tanimura, Yoshitaka
145
(
22
)
20161213 , American Institute of Physics Inc.
ISSN:00219606
内容記述
We consider a quantum system strongly coupled to multiple heat baths at different temperatures. Quantum heat transport phenomena in this system are investigated using two definitions of the heat current: one in terms of the system energy and the other in terms of the bath energy. When we consider correlations among systembath interactions (CASBIs)  which have a purely quantum mechanical origin  the definition in terms of the bath energy becomes different. We found that CASBIs are necessary to maintain the consistency of the heat current with thermodynamic laws in the case of strong systembath coupling. However, within the context of the quantum master equation approach, both of these definitions are identical. Through a numerical investigation, we demonstrate this point for a nonequilibrium spinboson model and a threelevel heat engine model using the reduced hierarchal equations of motion approach under the strongly coupled and nonMarkovian conditions. We observe the cyclic behavior of the heat currents and the work performed by the heat engine, and we find that their phases depend on the systembath coupling strength. Through consideration of the bath heat current, we show that the efficiency of the heat engine decreases as the strength of the systembath coupling increases, due to the CASBI contribution. In the case of a large systembath coupling, the efficiency decreases further if the bath temperature is increased, even if the ratio of the bath temperatures is fixed, due to the discretized nature of energy eigenstates. This is also considered to be a unique feature of quantum heat engines.
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http://repository.kulib.kyotou.ac.jp/dspace/bitstream/2433/218328/1/1.4971370.pdf