Quantum open system in the strong coupling regime

Non-equilibrium devices exploit energy/particles currents that flow through a system coupled to multiple baths. Although the fluxes increase in the weak coupling regime as the coupling strengthens, why they decrease to zero for large coupling values remains unknown. This turnover effect has been predicted in several systems, such as photosynthetic complexes, mesoscopic junctions, heat machines and chemical networks, without a single counterexample. We use scattering theory to study heat currents in the strong coupling regime for an open quantum system far from equilibrium. We classified the different possibilities given different scattering potentials and we showed cases where the heat current does not converge to zero when the coupling strength increases to infinity. We also saw cases where the heat current behaves as a wave, with the frequency decreasing with the coupling strength. Such effects depend on the structure of the interaction operator.