Numerically "exact" simulations of a quantum Carnot cycle: Analysis using thermodynamic work diagrams
Abstract
We investigate the efficiency of a quantum Carnot engine based on open quantum dynamics theory. The model includes timedependent external fields for the subsystems controlling the isothermal and isentropic processes and for the systembath (SB) interactions controlling the transition between these processes. Numerical simulations are conducted in a nonperturbative and nonMarkovian SB coupling regime by using the hierarchical equations of motion under these fields at different cycle frequencies. The work applied to the total system and the heat exchanged with the baths are rigorously evaluated. In addition, by regarding quasistatic work as free energy, we compute the quantum thermodynamic variables and analyze the simulation results by using thermodynamic work diagrams for the first time. Analysis of these diagrams indicates that, in the strong SB coupling region, the fields for the SB interactions are major sources of work, while in other regions, the field for the subsystem is a source of work. We find that the maximum efficiency is achieved in the quasistatic case and is determined solely by the bath temperatures, regardless of the SB coupling strength, which is a numerical manifestation of Carnot's theorem.
 Publication:

Journal of Chemical Physics
 Pub Date:
 August 2022
 DOI:
 10.1063/5.0107305
 arXiv:
 arXiv:2205.09487
 Bibcode:
 2022JChPh.157h4110K
 Keywords:

 Condensed Matter  Statistical Mechanics;
 Physics  Chemical Physics;
 Quantum Physics
 EPrint:
 13 pages, 6 figures, 3 tables