Minimizing Dissipation via Interacting Environments: Quadratic Convergence to Landauer Bound

We explore the fundamental limits on thermodynamic irreversibility when cooling a quantum system in the presence of a finite-size reservoir. First, we prove that for any non-interacting $n$-particle reservoir, the entropy production $\mathrm{\Sigma }$ decays at most linearly with $n$. Instead, we derive a cooling protocol in which $\mathrm{\Sigma }\propto 1\mathrm{/}{n}^2$, which is in fact the best possible scaling. This becomes possible due to the presence of interactions in the finite-size reservoir, which must be prepared at the verge of a phase transition. Our results open the possibility of cooling with a higher energetic efficiency via interacting reservoirs.