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Entropy transport through a superfluid quantum point contact: A Keldysh field-theory approach

Davide Bertolusso1,*, C. J. Bolech1,2, and Thierry Giamarchi1

  • *Contact author: davide.bertolusso@unige.ch
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Phys. Rev. Research 8, 043066 – Published 19 October, 2026

DOI: https://doi.org/10.1103/rxbq-74f6

Abstract

We study the matter and entropy transport between two ultracold neutral Fermi-gas reservoirs linked by a quantum point contact under a chemical-potential gradient. We describe the two leads with a BCS mean-field model and derive the current-bias characteristics for both particle and entropy transport. We compute the out-of-equilibrium steady-state currents by using the Keldysh formalism. In accordance with previous works in the literature, we confirm the well-known behavior for the particle current and extend the computation to the entropy current in the BCS regime. The entropy current shows an oscillatory behavior at low voltage in the ballistic junction limit. We analyze the results for a wide range of values of the junction's transparency. We also compare our findings with experimental results in cold atomic gases in the unitary regime.

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Phys. Rev. Research 8, 043066– Published 19 October, 2026
  • Received 1 May 2026
  • Accepted 17 August 2026
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