Non-equilibrium dynamics of quantum absorption refrigerator at Liouvillian exceptional points: critical damping and better performance

Abstract We explore how Liouvillian exceptional points (LEPs) shape the non-equilibrium dynamics and performance of a three-level quantum absorption refrigerator (QAR). While most studies focus on steady-state operation, we demonstrate that the non-equilibrium dynamics near LEPs play a crucial role. At third-order LEPs, we derive the conditions for critical damping, which leads to the fastest convergence of both the system state and heat currents. Remarkably, non-equilibrium contributions can enhance heat transfer from the cold to the hot bath at reduced work cost, yielding a higher coefficient of performance (COP). By tuning the relative weights of these contributions, we demonstrate a strategy to optimize QAR performance focusing on the initial heat current from the cold bath. The influence of the non-equilibrium process is inevitable and accumulates, resulting in a larger total heat absorption and a higher accumulated COP than in the equilibrium case. These results highlight LEPs as a resource for accelerating relaxation and enhancing efficiency, offering practical guidance for the design of high-performance quantum thermal machines.