Geometric properties of adiabatic quantum thermal machines

A quantum thermal machine can be controlled by time-periodic perturbations that define a cycle, as in conventional macroscopic thermal machines. This paper presents a general and unified approach to the study of quantum thermal machines, including both heat engines and refrigerators, which operate under periodic adiabatic driving and are in contact with thermal reservoirs kept at different temperatures. Importantly, many observables characterizing the operation and the performance of these machines are geometric in nature.