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- Title
- Steady-state Quantum Thermodynamics with Synthetic Negative Temperatures
- KIAS Author
- Singh, Varinder
- Journal
- Physical Review Research, 2024
- Archive
-
arXiv:2305.01215
- Abstract
- A bath with a negative temperature is a subject of intense debate in recent times. It raises fundamental
questions not only on our understanding of negative temperature of a bath in connection with thermodynamics
but also on the possibilities of constructing devices using such baths. In this work, we study steady-state quantum
thermodynamics involving baths with negative temperatures. A bath with a negative temperature is created
synthetically using two baths of positive temperatures and weakly coupling these with a qutrit system. These
baths are then coupled to each other via a working system. At steady state, the laws of thermodynamics are
analyzed. We find that whenever the temperatures of these synthetic baths are identical, there is no heat flow,
which reaffirms the zeroth law. There is always a spontaneous heat flow for different temperatures. In particular,
heat flows from a bath with a negative temperature to a bath with a positive temperature which, in turn, implies
that a bath with a negative temperature is “hotter” than a bath with a positive temperature. This warrants
an amendment in the Kelvin-Planck statement of the second law, as suggested in earlier studies. In all these
processes, the overall entropy production is positive, as required by the Clausius statement of the second law.
We construct continuous heat engines operating between positive and negative temperature baths. These engines
yield maximum possible heat-to-work conversion efficiency, that is, unity. We also study the thermodynamic
nature of heat from a bath with a negative temperature and find that it is thermodynamic work but with negative
entropy.