Enhancing optomechanical cooling through breaking time-reversal symmetry

he question whether the efficiency of thermodynamic devices such as heat engines and refrigeration is altered through the breaking of time-reversal symmetry has been a topic of significant debate. We experimentally investigate the cooling of nanomechanical resonators in multimode optomechanical devices, in which time-reversal symmetry for thermal fluctuations can be broken through suitable temporal modulation of the radiation pressure control field. We study the resultant nonreciprocal transport of thermal vibrations, and show that the controlled breaking of time-reversal symmetry through synthetic magnetic fields can enhance the cooling performance, yielding lower phonon occupancies than the conventional limit.