Non-Thermal Aging and Cooling of Supercooled Liquids in Microcavities

Supercooled liquids depart from equilibrium below the glass transition temperature due to dramatic slowdown in structural relaxation. Below this point, they undergo physical aging, during which material properties slowly drift toward equilibrium over astronomical timescales. In this work, we demonstrate that placing molecular supercooled liquids inside Fabry-Pérot cavities induces nonthermal aging via strong light-matter coupling. Cavity electromagnetic modes selectively pump energy into intramolecular vibrations, creating an energy imbalance that drives structural degrees of freedom into deeper potential minima. Using established principles of physical aging, including time-reparameterization softness and material-time translational invariance, we collapse nonequilibrium intermediate scattering functions (ISFs) onto their equilibrium counterparts, revealing that cavity aging traverses sequences of equilibrium states despite being a nonequilibrium protocol. We exploit this finding to develop the cavity configurational feedback cooling protocol, which combines time-modulation of the light-matter coupling strength with feedback control to prepare equilibrium supercooled liquids at ultralow temperatures near the glass transition, bypassing the need for millions of years of brute-force molecular dynamics (MD) simulations. These results demonstrate that strong light-matter interactions provide a transformative route to access ultralow-temperature equilibrium states in supercooled liquids.