Steady-state thermodynamics of non-interacting transport beyond weak coupling

TL;DR

This paper derives exact expressions for steady-state matter and energy currents in non-interacting transport models beyond weak coupling, demonstrating the impact of coupling strength on thermodynamic efficiency.

Contribution

It provides exact solutions for non-interacting transport beyond weak coupling and analyzes how increased coupling affects thermodynamic efficiency.

Findings

Positivity of entropy production rate is explicitly shown.

Exact stationary current expressions are derived.

Efficiency decreases with stronger system-reservoir coupling.

Abstract

We investigate the thermodynamics of simple (non-interacting) transport models beyond the scope of weak coupling. For a single fermionic or bosonic level -- tunnel-coupled to two reservoirs -- exact expressions for the stationary matter and energy current are derived from the solutions of the Heisenberg equations of motion. The positivity of the steady-state entropy production rate is demonstrated explicitly. Finally, for a configuration in which particles are pumped upwards in chemical potential by a downward temperature gradient, we demonstrate that the thermodynamic efficiency of this process decreases when the coupling strength between system and reservoirs is increased, as a direct consequence of the loss of a tight coupling between energy and matter currents.